Texas Instruments | HDC2021 High-Accuracy, Low-Power Humidity and Temperature Sensor With Assembly Protection Cover | Datasheet | Texas Instruments HDC2021 High-Accuracy, Low-Power Humidity and Temperature Sensor With Assembly Protection Cover Datasheet

Texas Instruments HDC2021 High-Accuracy, Low-Power Humidity and Temperature Sensor With Assembly Protection Cover Datasheet
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HDC2021
SNAS773 – DECEMBER 2019
1 Features
3 Description
•
The HDC2021 is an integrated relative humidity and
temperature sensor with a factory-installed polyimide
tape cover over the opening of the relative humidity
sensor element. The tape cover provides protection
against pollutants that can appear in certain stages of
the manufacturing process, such as SMT assembly,
PCB board wash, and conformal coating. The tape
design allows for a full conformal coating of the PCB,
and includes an adhesive free corner tab for quick
removal using a pair of tweezers.
1
•
•
•
•
•
•
•
•
•
•
Factory-installed polyimide tape to protect sensor
during assembly
Backward-compatible with HDC2080
RH measurement range: 0% to 100%
Temperature measurement range: –40°C to
125°C
Supply voltage range: 1.62 V to 3.6 V
I2C interface compatibility
±2% RH sensor accuracy
±0.2°C temperature sensor accuracy
50-nA sleep mode current
550-nA average supply current (11-bit, 1
measurement/second)
Available auto measurement mode
2 Applications
•
•
•
•
•
•
•
Thermostats
Smart speakers (with voice assistant)
Washers and dryers
HVAC sensor transmitters (temperature, pressure,
and humidity)
HVAC system controllers
Wireless environmental sensors
Home printers
Typical Application
The HDC2021 device is backward-compatible with
the
HDC2080,
providing
high
accuracy
measurements with very low power consumption in a
small DFN package. The capacitive-based sensor
includes new integrated digital features and a heating
element to dissipate condensation and moisture. The
HDC2021 digital features include programmable
interrupt thresholds to provide alerts and system
wake-ups without requiring a microcontroller to
continuously monitor the system. Combined with
programmable sampling intervals, low power
consumption, and 1.8-V supply voltage support, the
HDC2021 is designed for ultra-low power batteryoperated systems.
Device Information(1)
PART NUMBER
HDC2021
BODY SIZE (NOM)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
RH Accuracy (TA = 30°C)
1.80 V
VDD
HDC2021
PACKAGE
WSON (6)
VDD
10
Typical
SCL
I2 C
Master
SDA
ADC
Registers
+
Logic
Temperature
Sensor
I2 C
DRDY/INT
9
8
GPIO
ADDR
MCU
Calibration
GND
GND
Accuracy (r%RH)
RH
Sensor
7
6
5
4
3
2
1
0
0
10
20
30
40
50
60
70
80
90
100
RH (%RH)
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. ADVANCE INFORMATION for pre-production products; subject to
change without notice.
ADVANCE INFORMATION
HDC2021 High-Accuracy, Low-Power Humidity and Temperature Sensor With Assembly
Protection Cover
HDC2021
SNAS773 – DECEMBER 2019
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Description (continued).........................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
4
4
4
4
5
6
6
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Switching Characteristics ..........................................
Timing Diagram.........................................................
Typical Characteristics ..............................................
8.4 Device Functional Modes........................................ 15
8.5 Programming .......................................................... 15
8.6 Register Maps ......................................................... 17
9
Application and Implementation ........................ 28
9.1 Application Information............................................ 28
9.2 Typical Application ................................................. 28
10 Power Supply Recommendations ..................... 30
11 Layout................................................................... 30
11.1 Layout Guidelines ................................................. 30
11.2 Layout Example .................................................... 31
12 Device and Documentation Support ................. 32
12.1
12.2
12.3
12.4
12.5
12.6
Detailed Description .............................................. 8
ADVANCE INFORMATION
8.1 Overview ................................................................... 8
8.2 Functional Block Diagram ......................................... 8
8.3 Feature Description................................................... 9
Documentation Support .......................................
Receiving Notification of Documentation Updates
Support Resources ...............................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
32
32
32
32
32
32
13 Mechanical, Packaging, and Orderable
Information ........................................................... 32
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
2
DATE
REVISION
NOTES
December 2019
*
Initial release.
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5 Description (continued)
The HDC2021 provides high-accuracy measurement capability for a wide range of environmental monitoring and
Internet of Things (IoT) applications such as smart thermostats and smart home assistants.
For applications with strict power-budget restrictions, Auto Measurement Mode enables the HDC2021 to
automatically initiate temperature and humidity measurements. This feature allows users to configure a
microcontroller into deep sleep mode because the HDC2021 is no longer dependent upon the microcontroller to
initiate a measurement.
Programable temperature and humidity thresholds in the HDC2021 allow the device to send a hardware interrupt
to wake up the microcontroller when necessary. In addition, the power consumption of the HDC2021 is
significantly reduced, which can help minimize self-heating and improve measurement accuracy.
The HDC2021 is factory-calibrated to ±0.2°C temperature accuracy and ±2% relative humidity accuracy.
6 Pin Configuration and Functions
SDA
1
6
SCL
GND
2
5
VDD
ADDR
3
4
DRDY/INT
ADVANCE INFORMATION
DEB Package
6-Pin WSON
Transparent Top View
Pin Functions
PIN
NAME
NO.
TYPE (1)
DESCRIPTION
ADDR
3
I
Address select pin – leave unconnected or hardwired to VDD or GND.
Unconnected slave address: 1000000X
GND: slave address: 1000000X
VDD: slave address: 1000001X
where 'X' represents the read-write (R/W) bit.
DRDY/INT
4
O
Data ready/Interrupt. Push-Pull Output.
GND
2
G
Ground
SCL
6
I
Serial clock line for I2C, open-drain. Requires a pullup resistor to VDD.
SDA
1
I/O
Serial data line for I2C, open-drain. Requires a pullup resistor to VDD.
VDD
5
P
(1)
Positive Supply Voltage
The definitions below define the functionality of the TYPE cells for each pin:
(a) I = input
(b) O = output
(c) I/O = input/output
(d) G = ground
(e) P = power
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
VDD
Applied Voltage on VDD pin
–0.3
3.9
V
GND
Applied Voltage on GND pin
–0.3
3.9
V
ADDR
Applied Voltage on ADDR pin
–0.3
3.9
V
SCL
Applied Voltage on SCL pin
–0.3
3.9
V
SDA
Applied Voltage on SDA pin
–0.3
3.9
V
Tstg
Storage temperature
–65
150
°C
(1)
UNIT
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
7.2 ESD Ratings
VALUE
ADVANCE INFORMATION
Electrostatic
discharge
V(ESD)
(1)
(2)
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2000
Charged device model (CDM), per JEDEC specification JESD22-C101 (2)
±500
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
PARAMETER
MIN
MAX
UNIT
VDD
Supply voltage
1.62
3.6
V
TTEMP
Temperature Sensor - Operating free-air temperature
–40
125
°C
TRH
Relative Humidity Sensor - Operating free-air temperature
–20
70
°C
–40
85
°C
THEATER Integrated Heater - Operating free-air temperature
7.4 Thermal Information
HDC2021
THERMAL METRIC
(1)
WSON (DEB)
UNIT
6 PINS
RθJA
Junction-to-ambient thermal resistance
57.9
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
58.7
°C/W
RθJB
Junction-to-board thermal resistance
27.0
°C/W
ΨJT
Junction-to-top characterization parameter
5.6
°C/W
ΨJB
Junction-to-board characterization parameter
26.9
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
16.5
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
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7.5 Electrical Characteristics
TA = 30°C, VDD = 1.8 V, 20% ≤ RH ≤ 80% (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
POWER CONSUMPTION
IDD
Supply Current
Averaged at 1 sample per second
RH & TEMP sensor (1) (2)
IDD
Supply Current
Averaged at 1 sample every two seconds
RH & TEMP sensor (1) (2)
IDD
Supply Current
No Measurement (Sleep Mode)
(1)
0.55
µA
0.3
µA
0.05
0.1
µA
650
890
µA
550
730
µA
IDD
Supply Current
During RH measurement
IDD
Supply Current
During TEMP measurement (1)
IDD
Supply Current
Startup (average on startup time)
80
µA
IHEATER
Integrated Heater (enabled)
VDD = 3.3V; THEATER - TA = 80°C
Steady state measurement
90
mA
RELATIVE HUMIDITY SENSOR
Accuracy (3) (4) (5)
RHREP
Repeatability (6)
RHHYS
Hysteresis (7)
±2
14 bit resolution
(8)
t63% step
(9)
±3
%RH
±0.1
%RH
±1
%RH
RHHYS
Response Time
8
s
RHCT
Conversion Time (6)
9 bit resolution
275
µs
RHCT
Conversion Time (6)
11 bit resolution
400
µs
RHCT
Conversion Time
(6)
14 bit resolution
RHOR
Operating Range
RHLTD
Long-term Drift (11)
Non-condensing (10)
660
0
µs
100
±0.25
%RH
%RH/yr
TEMPERATURE SENSOR
TEMPACC
Accuracy (6)
5°C ≤ TA ≤ 60°C
±0.2
±0.7
°C
TEMPACC
Accuracy (6)
10°C ≤ TA ≤ 35°C
±0.2
±0.4
°C
TEMPREP
Repeatability (6)
14 bit resolution
±0.1
°C
(6)
TEMPCT
Conversion Time
9 bit resolution
225
µs
TEMPCT
Conversion Time (6)
11 bit resolution
350
µs
TEMPCT
Conversion Time (6)
14 bit resolution
610
µs
(1)
(2)
(3)
(4)
Does not include I2C read/write communication or pullup resistor current through SCL and SDA
Average current consumption while conversion is in progress
Excludes hysteresis and long-term drift
Excludes the impact of dust, gas phase solvents and other contaminents such as vapors from packaging materials, adhesives, or tapes,
etc.
(5) Limits apply over the humidity operating 20% to 80% RH (non-condensing) from 0°C to 60°C
(6) This parameter is specified by design and/or characterization and is not tested in production
(7) The hysteresis value is the difference between the RH measurement in a rising and falling RH environment, at a specific RH point
(8) Actual response times will vary dependent on system thermal mass and air-flow
(9) Time for the RH output to change by 63% of the total RH change after a step change in environmental humidity
(10) Recommneded humidity operating range is 20% to 80% RH (non-condensing) over 0°C to 60°C. Prolonged operation beyond these
ranges may result in a shift of sensor reading, with slow recovery time
(11) Drift due to aging effects at typical conditions (30°C and 20% to 50% RH). This value may be impacted by dust, vaporized solvents,
outgassing tapes, adhesives, packaging materials, etc.
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ADVANCE INFORMATION
RHACC
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Electrical Characteristics (continued)
TA = 30°C, VDD = 1.8 V, 20% ≤ RH ≤ 80% (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SCL, SDA PINS
VIH
HIGH-level input voltage
VIL
LOW-level input voltage
VOL
LOW-level output voltage
0.7 x
VDD
V
IOL = 3 mA
0.3 x
VDD
V
0.4
V
7.6 Switching Characteristics
TA = 30°C, VDD = 1.8V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
400
kHz
SCL, SDA PINS
ADVANCE INFORMATION
fSCL
SCL clock frequency (1)
10
tLOW
LOW period of the SCL clock (1)
1.3
µs
0.6
µs
tHIGH
(1)
High period of the SCL clock
(1)
This parameter is specified by design and/or characterization and is not tested in production
7.7 Timing Diagram
SDA
tLOW
tSP
SCL
tHIGH
START
REPEATED
START
STOP
START
Figure 1. I2C Timing
6
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7.8 Typical Characteristics
Unless otherwise noted, TA = 30°C, VDD = 1.8 V.
1
10
Typical
9
0.9
8
0.8
7
0.7
Accuracy (r°C)
6
5
4
0.6
0.5
0.4
3
0.3
2
0.2
1
0.1
0
-40
0
0
10
20
30
40
50
60
70
80
90
100
-25
-10
5
20
700
750
700
80
95
110
125
VDD = 1.71V
VDD = 1.8V
VDD = 2.5V
VDD = 3V
VDD = 3.3V
VDD = 3.6V
650
IDD (nA)
IDD (nA)
650
600
600
550
550
500
500
450
450
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
400
-40
3.6
-15
10
35
60
85
110
125
Temp (°C)
VDD (V)
Figure 4. Supply Current vs. Supply Voltage, Average at 1
Measurement/Second, RH (11-Bit) and Temperature (11-Bit)
Figure 5. Supply Current vs. Temperature, Average at 1
Measurement/Second, RH (11-Bit) and Temperature (11-Bit)
400
400
T = -40°C
T = -20°C
T = 0°C
T = 25°C
T = 50°C
T = 85°C
T = 125°C
350
300
350
300
250
VDD = 1.71V
VDD = 1.8V
VDD = 2.5V
VDD = 3V
VDD = 3.3V
VDD = 3.6V
250
IDD (nA)
IDD (nA)
65
800
T = -40°C
T = -20°C
T = 0°C
T = 25°C
T = 85°C
T = 125°C
750
200
200
150
150
100
100
50
50
0
1.6
50
Figure 3. Temperature Accuracy vs. Temperature Set Point
Figure 2. RH Accuracy vs. RH Set Point
800
400
1.6
35
Temp (°C)
RH (%RH)
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
0
-40
-15
10
35
60
85
110
125
Temp (°C)
VDD (V)
Figure 6. Supply Current vs. Supply Voltage, Sleep Mode
Figure 7. Supply Current vs. Temperature, Sleep Mode
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ADVANCE INFORMATION
Accuracy (r%RH)
Typical
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8 Detailed Description
8.1 Overview
The HDC2021 is a highly integrated digital humidity and temperature sensor that incorporates both humiditysensing and temperature-sensing elements, an analog-to-digital converter, calibration memory, and an I2C
interface that are all contained in a 3.00-mm × 3.00-mm, 6-pin WSON package. The HDC2021 provides excellent
measurement accuracy with very low power consumption and features programmable resolution for both
humidity and temperature:
• Temperature resolution [9, 11, or 14 bits]
• Humidity resolution [9, 11, or 14 bits]
The conversion time during measurements is dependent upon the configured resolution for humidity and
temperature, which can be configured for optimal power consumption.
ADVANCE INFORMATION
The HDC2021 device incorporates a state-of-the-art polymer dielectric to provide capacitive-sensing
measurements. As with most relative humidity sensors that include this type of technology, the user must meet
these application requirements to ensure optimal device performance for the sensing element:
• Follow the correct storage and handling procedures during board assembly. See Humidity Sensor: Storage
and Handling Guidelines. (SNIA025) for these guidelines.
• Protect the sensor from contaminants during operation.
• Reduce prolonged exposure to both high temperature and humidity extremes that may impact sensor
accuracy.
• Follow the correct layout guidelines for best performance. See Optimizing Placement and Routing for
Humidity Sensors (SNAA297) for these guidelines.
8.2 Functional Block Diagram
VDD
HDC2021
SCL
RH
Sensor
SDA
ADC
Registers
+
Logic
Temperature
Sensor
I2C
DRDY/INT
ADDR
Calibration
GND
8
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8.3 Feature Description
8.3.1 Factory Installed Polyimide Tape
A polyimide tape covers the opening of the humidity sensor element. The tape protects the humidity sensor
element from pollutants that can be produced as part of the manufacturing process, such as SMT assembly,
PCB board wash, and conformal coating. The tape must be removed after the final stages of assembly for
accurate measurement of relative humidity in the ambient environment. The tape can withstand at least three
standard reflow cycles.
To remove the polyimide tape from the humidity sensor element, TI recommends to use a ESD-safe tweezer to
grip the adhesive free tab in the lower right corner, then slowly peel from the bottom right corner towards the top
left corner (pin 1 designator) in an upward direction (as opposed to across the surface). This will help to reduce
the risk of scratching the humidity sensor element.
8.3.2 Sleep Mode Power Consumption
8.3.3 Measurement Modes: Trigger on Demand vs. Auto Measurement
The two types of measurement modes are available on the HDC2021: Trigger on Demand and Auto Mode.
Trigger on Demand is when each measurement reading is initiated through an I2C command on an as-needed
basis. After the measurement is converted, the device remains in sleep mode until another I2C command is
received.
The HDC2021 can perform measurement readings on a periodic basis in auto measurement mode to eliminate
the need to initiate a measurement request through an I2C command and improve power consumption. The user
can adjust the Soft Reset and Interrupt Configuration register to select one of 7 different sampling rates (the
range spans from 1 sample every 2 minutes to 5 samples every second). In auto measurement mode, the
HDC2021 wakes up from sleep to measurement mode based on the selected sampling rate.
8.3.4 Heater
The HDC2021 includes an integrated heating element that can be switched on briefly to prevent or remove any
condensation that may build up in high humidity environments. Additionally, the heater can be used to verify
functionally of the integrated temperature sensor. The operating range of the heater should be limited to –40°C to
85°C. The heater will have a typical current draw of 90 mA at 3.3-V operation and 55 mA at 1.8-V operation.
8.3.5 Interrupt Description
NOTE
When multiple bits are enabled, the DRDY/INT pin can only reflect the status of one
interrupt bit at a time. The DRDY/INT pin DOES NOT function as the logical ‘OR’ of
interrupt bits that have been enabled.
The highest priority is given to TH_ENABLE bit, followed by TL_ENABLE, HH_ENABLE,
and HL_ENABLE bits in descending order. Therefore, programming recommendations are
provided as below:
• The DRDY/INT will track the HL_ENABLE, if enabled, and all other ENABLE bits are
disabled.
• The DRDY/INT will track the HH_ENABLE, if enabled, and the TH_ENABLE and
TL_ENABLE are disabled.
• The DRDY/INT will track the TL_ENABLE, if enabled, and the TH_ENABLE is
disabled.
• The DRDY/INT will track the TH_ENABLE, if enabled, and is independent of other
ENABLE bit settings.
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ADVANCE INFORMATION
One key feature of the HDC2021 is the low power consumption designed for battery-powered or energyharvesting applications. In these applications, the HDC2021 spends most of the time in sleep mode that has a
typical current consumption of 50 nA. This minimizes the average power consumption and self-heating.
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Feature Description (continued)
8.3.5.1 DRDY
When DRDY_ENABLE is enabled, and a humidity and/or temperature conversion is complete, the
DRDY_STATUS bit asserts to 1. To enable the DRDY/INT pin of HDC2021, the DRDY/INT_EN bit (0x0E bit[2])
must be set to 1 and the INT_MOD bit should be set to 0. If these bits are not configured, the pin will be left in
high impedance. The INT_POL bit of this register defines the interrupt polarity of the DRDY/INT pin. Figure 8 and
Figure 9 display the output behavior of the DRDY/INT pin for both interrupt polarity cases: INT_POL= 0 and
INT_POL= 1.
Previous Data
New Data Available
1
DRDY_STATUS
0
VDD
DRDY/INT
[INT_POL = 1]
ADVANCE INFORMATION
0
Figure 8. Data Ready Interrupt - Active High (INT_POL = 1)
Previous Data
New Data Available
1
DRDY_STATUS
0
VDD
DRDY/INT
[INT_POL = 0]
0
Figure 9. Data Ready Interrupt - Active Low (INT_POL = 0)
10
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Feature Description (continued)
8.3.6 INTERRUPT on Threshold
8.3.6.1 Temperature High
When TH_ENABLE is enabled and the temperature is over the programmed threshold level stored in the
Temperature Threshold HIGH register, the TH_STATUS bit asserts to 1. The polarity and interrupt mode of the
TH_STATUS bit and the DRDY/INT pin can be configured through the INT_POL and INT_MODE bits of Register
0x0E.
The INT_MODE bit sets the threshold to either comparator mode or a level-sensitive alarm.
When INT_MODE is set to 0, the TH_STATUS bit remains set to 1 until it is read. The polarity of the DRDY/INT
pin is set by INT_POL.
When INT_MODE is set to 1, the TH_STATUS bit is based on the current temperature conversion. The polarity
of the DRDY/INT pin is set by INT_POL.
Temperature Threshold High
Time
1
TH_STATUS
[INT_MODE = 0]
TH_STATUS Bit Read
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 0]
0
1
TH_STATUS
[INT_MODE = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 0]
0
Figure 10. INTERRUPT on Threshold - Temperature High
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ADVANCE INFORMATION
T [°C]
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Feature Description (continued)
8.3.6.2 Temperature Low
When TL_ENABLE is set, and the temperature is under the threshold value program in the Temperature
Threshold LOW register, the TL_STATUS bit is set to 1. The TL_STATUS bit and the DRDY/INT pin behave
based on the INT_POL and INT_MODE bits.
The INT_MODE bit sets the threshold to either comparator mode or a level-sensitive alarm.
When INT_MODE is set to 0, the TL_STATUS bit remains set to 1 until it is read. The polarity of the DRDY/INT
pin is set by INT_POL.
When INT_MODE is set to 1, the TL_STATUS bit is based on the current temperature conversion. The polarity of
the DRDY/INT pin is set by INT_POL.
T [°C]
ADVANCE INFORMATION
Temperature Threshold Low
Time
1
TL_STATUS
[INT_MODE = 0]
TL_STATUS Bit Read
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 0]
0
1
TL_STATUS
[INT_MODE = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 0]
0
Figure 11. INTERRUPT on Threshold - Temperature Low
12
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Feature Description (continued)
8.3.6.3 Humidity High
When HH_ENABLE is set and the humidity is over the threshold value program in the Humidity Threshold HIGH
register, the HH_STATUS bit is set to 1. The HH_STATUS bit and the DRDY/INT pin behave based on the
INT_POL and INT_MODE bits.
The INT_MODE bit sets the threshold to either comparator mode or a level-sensitive alarm.
When INT_MODE is set to 0, the HH_STATUS bit remains set to 1 until it is read. The polarity of the DRDY/INT
pin is set by INT_POL.
When INT_MODE is set to 1, the HH_STATUS bit is based on the current temperature conversion. The polarity
of the DRDY/INT pin is set by INT_POL.
H [%RH]
Time
1
HH_STATUS
[INT_MODE = 0]
HH_STATUS Bit Read
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 0]
0
1
HH_STATUS
[INT_MODE = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 0]
0
Figure 12. INTERRUPT on Threshold - Humidity High
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Feature Description (continued)
8.3.6.4 Humidity Low
When HL_ENALBE is set, and the humidity is over the threshold value program in the Humidity Threshold LOW
register, the HL_STATUS bit is set to 1. The HL_STATUS bit and the DRDY/INT pin behave based on the
INT_POL and INT_MODE bits.
The INT_MODE bit sets the threshold to either comparator mode or a level-sensitive alarm.
When INT_MODE is set to 0, the HL_STATUS bit remains set to 1 until it is read. The polarity of the DRDY/INT
pin is set by INT_POL.
When INT_MODE is set to 1, the HL_STATUS bit is based on the current temperature conversion. The polarity
of the DRDY/INT pin is set by INT_POL.
H [%RH]
ADVANCE INFORMATION
Humidity Threshold Low
Time
1
HL_STATUS
[INT_MODE = 0]
HL_STATUS Bit Read
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 0]
[INT_POL = 0]
0
1
HL_STATUS
[INT_MODE = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 1]
0
VDD
DRDY/INT
[INT_MODE = 1]
[INT_POL = 0]
0
Figure 13. INTERRUPT on Threshold - Humidity Low
14
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8.4 Device Functional Modes
The HDC2021 has two modes of operation: sleep mode and measurement mode.
8.4.1 Sleep Mode vs. Measurement Mode
After power up, the HDC2021 defaults to sleep mode and waits for an I2C instruction to set programmable
conversion times, trigger a measurement or conversion, or read or write valid data. When a measurement is
triggered, the HDC2021 switches to measurement mode that converts temperature or humidity values from
integrated sensors through an internal ADC and stores the information in their respective data registers. The
DRDY/INT pin can be monitored to verify if data is ready after measurement conversion. The DRDY/INT pin
polarity and interrupt mode are set according to the configuration of the Interrupt Enable and DRDY/INT
Configuration registers. After completing the conversion, the HDC2021 returns to sleep mode.
8.5 Programming
To communicate with the HDC2021, the master must first address slave devices through a slave address byte.
The slave address byte consists of seven address bits and a direction bit that indicates the intent to execute a
read or write operation. The HDC2021 features an address pin to allow up to 2 devices to be addressed on a
single bus. Table 1 describes the pin logic levels used to connect up to two devices, with 'X' representing the
read-write (R/W) bit. ADDR should be set before any activity on the interface occurs and remain constant while
the device is powered up.
Table 1. HDC2021 I2C Slave Address
ADDR
ADDRESS
GND
1000000X
VDD
1000001X
8.5.2 I2C Interface
The HDC2021 operates only as a slave device on the I2C bus interface. It is not allowed to have multiple devices
on the same I2C bus with the same address. Connection to the bus is made through the open-drain lines: SDA,
and SCL. The SDA and SCL pins feature integrated spike-suppression filters and Schmitt triggers to minimize
the effects of input spikes and bus noise. After power-up, the sensor needs at least 3 ms to be ready to start RH
and temperature measurement. After power-up the sensor is in sleep mode until a communication or
measurement is performed. All data bytes are transmitted MSB first.
8.5.3 Serial Bus Address
To communicate with the HDC2021, the master must first address slave devices through a slave address byte.
The slave address byte consists of seven address bits, and a direction bit that indicates the intent to execute a
read or write operation.
8.5.4 Read and Write Operations
Address registers, which hold data pertaining to the status of the device, can be accessed and modified through
a pointer mechanism with the following write and read procedures. The register address value is the first byte
transferred after the device slave address byte with the R/W bit low. Every write operation to the HDC2021
requires a value for the register address (refer to Table 2).
When reading from the HDC2021, the current pointer location is used to determine which register is read by a
read operation. That pointer location points to the last written register address. To change the address for a read
operation, a new value must be written to the pointer. This transaction is accomplished by issuing the slave
address byte with the R/W bit set to 0, followed by the pointer byte. No additional data is required (refer to
Table 4).
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8.5.1 I2C Serial Bus Address Configuration
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The master can then generate a START condition and send the slave address byte with the R/W bit set to 1 to
initiate the read command. The address register is incremented automatically to enable the multibyte read and
write operation (refer to Table 3 and Table 5). Note that register bytes are sent MSB first, followed by the LSB. A
write operation in a read-only register such as DEVICE ID, MANUFACTURER ID, or SERIAL ID returns a NACK
after each data byte. A read or write operation to an unused address returns a NACK after the pointer, and a
read or write operation with incorrect I2C address returns a NACK after the I2C address.
Table 2. Write Single Byte
Master
START
Slave address (W)
Address
Slave
DATA
ACK
STOP
ACK
ACK
Table 3. Write Multibyte
Master
START
Slave address (W)
Address
Slave
ACK
DATA
ACK
DATA
ACK
………
ACK
STOP
Table 4. Read Single Byte
Master
START
Slave address (R)
ADVANCE INFORMATION
Slave
Address
Start
ACK
Slave address (R)
ACK
NACK
ACK
STOP
DATA
Table 5. Read Multibyte
Master START
Slave
16
Slave
address (R)
Address
ACK
Start
ACK
Slave
address (R)
ACK
ACK
DATA
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ACK
……
NACK
STOP
DATA
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8.6 Register Maps
The HDC2021 contains data registers that hold configuration information, temperature and humidity
measurement results, and status information.
ADDRESS (HEX)
NAME
RESET VALUE
DESCRIPTION
0x00
TEMPERATURE LOW
00000000
Temperature [7:0]
0x01
TEMPERATURE HIGH
00000000
Temperature [15:8]
0x02
HUMIDITY LOW
00000000
Humidity [7:0]
0x03
HUMIDITY HIGH
00000000
Humidity [15:8]
0x04
INTERRUPT/DRDY
00000000
DataReady and interrupt configuration
0x05
TEMPERATURE MAX
00000000
Maximum measured temperature
(Not supported in Auto Measurement Mode)
0x06
HUMIDITY MAX
00000000
Maximum measured humidity
(Not supported in Auto Measurement Mode)
0x07
INTERRUPT ENABLE
00000000
Interrupt Enable
0x08
TEMP_OFFSET_ADJUST
00000000
Temperature offset adjustment
0x09
HUM_OFFSET_ADJUST
00000000
Humidity offset adjustment
0x0A
TEMP_THR_L
00000000
Temperature Threshold Low
Temperature Threshold High
0x0B
TEMP_THR_H
11111111
0x0C
RH_THR_L
00000000
Humidity threshold Low
0x0D
RH_THR_H
11111111
Humidity threshold High
0x0E
RESET&DRDY/INT CONF
00000000
Soft Reset and Interrupt Configuration
0x0F
MEASUREMENT CONFIGURATION
00000000
Measurement configuration
0xFC
MANUFACTURER ID LOW
01001001
Manufacturer ID Low
0xFD
MANUFACTURER ID HIGH
01010100
Manufacturer ID High
0xFE
DEVICE ID LOW
11010000
Device ID Low
0xFF
DEVICE ID HIGH
00000111
Device ID High
ADVANCE INFORMATION
Table 6. Register Map
8.6.1 Address 0x00 Temperature LSB
Table 7. Address 0x00 Temperature LSB Register
7
6
5
4
3
2
1
0
TEMP[7:0]
Table 8. Address 0x00 Temperature LSB Field Descriptions
BIT
FIELD
[7:0]
TEMPERATURE [7:0]
TYPE
R
RESET
00000000
DESCRIPTION
Temperature LSB
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8.6.2 Address 0x01 Temperature MSB
The temperature register is a 16-bit result register in binary format. The result of the acquisition is always a 14-bit
value, while the resolution is related to one selected in Measurement Configuration register. The temperature
measurement must be read LSB first, followed by MSB.
Table 9. Address 0x01 Temperature MSB Register
7
6
5
4
3
2
1
0
TEMP[15:8]
Table 10. Address 0x01 Temperature MSB Field Descriptions
BIT
FIELD
[15:8]
TYPE
TEMPERATURE [15:8]
RESET
R
00000000
DESCRIPTION
Temperature MSB
The temperature can be calculated from the output data with Equation 1:
§ TEMPERATURE [15 : 0] ·
¨
¸ u 165 40
©
¹
216
Temperature (qC)
(1)
ADVANCE INFORMATION
8.6.3 Address 0x02 Humidity LSB
Table 11. Address 0x02 Humidity LSB Register
7
6
5
4
3
2
1
0
HUMIDITY[7:0]
Table 12. Address 0x02 Humidity LSB Field Descriptions
BIT
FIELD
[7:0]
TYPE
HUMIDITY [7:0]
RESET
R
00000000
DESCRIPTION
Humidity LSB
8.6.4 Address 0x03 Humidity MSB
The humidity register is a 16-bit result register in binary format. The result of the acquisition is always a 14 bit
value, while the resolution is related to one selected in Measurement Configuration register. The humidity
measurement must be read LSB first, followed by MSB.
Table 13. Address 0x03 Humidity MSB Register
7
6
5
4
3
HUMIDITY[15:8]
2
1
0
Table 14. Address 0x03 Humidity MSB Field Descriptions
BIT
FIELD
[15:8]
HUMIDITY[15:8]
TYPE
R
RESET
00000000
DESCRIPTION
Humidity MSB
The humidity can be calculated from the output data with Equation 2:
Humidity (%RH)
18
§ HUMIDITY [15 : 0] ·
¨
¸ u 100
216
©
¹
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8.6.5 Address 0x04 Interrupt DRDY
Table 15. Address 0x04 Interrupt DRDY Register
7
DRDY_STATUS
6
TH_STATUS
5
TL_STATUS
4
HH_STATUS
3
HL_STATUS
2
RES
1
RES
0
RES
Table 16. Address 0x04 Interrupt DRDY Field Descriptions
FIELD
TYPE
RESET
DESCRIPTION
7
DRDY_STATUS
R/W
0
DataReady bit status
0 = Data Not Ready
1 = Data Ready
DRDY_STATUS is cleared to 0 when read
6
TH_STATUS
R/W
0
Temperature threshold HIGH Interrupt status
0 = No interrupt
1 = Interrupt
TH_STATUS is cleared to 0 when read
5
TL_STATUS
R/W
0
Temperature threshold LOW Interrupt status
0 = No interrupt
1 = Interrupt
TL_STATUS is cleared to 0 when read
4
HH_STATUS
R/W
0
Humidity threshold HIGH Interrupt status
0 = No interrupt
1 = Interrupt
HH_STATUS is cleared to 0 when read
3
HL_STATUS
R/W
0
Humidity threshold LOW Interrupt status
0 = No interrupt
1 = Interrupt
HL_STATUS is cleared to 0 when read
2
RES
0
Reserved
1
RES
0
Reserved
0
RES
0
Reserved
DRDY_STATUS indicates that temperature and/or humidity conversion is terminated. This bit is cleared when the
Interrupt/DRDY register is read or the output registers TEMPERATURE_HIGH, TEMPERATURE_LOW,
HUMIDITY_HIGH and HUMIDITY_LOW are read.
The TL_STATUS indicates that the Temperature Threshold LOW value is exceeded. The behavior is defined by
0x0E Configuration register value. The bit is cleared when the register Interrupt DRDY is read.
The TH_STATUS indicates that the Temperature Threshold HIGH value is exceeded. The behavior is defined by
0x0E Configuration register value. The bit is cleared when the register Interrupt DRDY is read.
The HH_STATUS indicates that the Humidity Threshold HIGH value is exceeded. The behavior is defined by
0x0E Configuration register value. The bit is cleared when the register Interrupt DRDY is read.
The HL_STATUS indicates that the Humidity Threshold LOW value is exceeded. The behavior is defined by
0x0E Configuration register value. The bit is cleared when the register Interrupt DRDY is read.
DRDY/INT pin behaves like the STATUS bits based on the 0x0E Configuration register value.
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8.6.6 Address 0x05 Temperature MAX
This register implements temperature peak detector function. It stores the highest temperature value converted
after the power up. Value is reset at power up and/or with soft reset procedure.
Table 17. Address 0x05 Temperature MAX Register
7
6
5
4
3
TEMPERATUREMAX[7:0]
2
1
0
Table 18. Address 0x05 Temperature Max Field Descriptions
BIT
FIELD
[7:0]
TYPE
TEMPERATUREMAX[7:0]
R/W
RESET
00000000
DESCRIPTION
Stores maximum temperature measurement from all I2C read
requests for temperature
Not supported in Auto Measurement Mode
The temperature can be calculated from the output data with Equation 3:
Temperature (qC)
§ TEMPERATURE [7 : 0] ·
¨
¸ u 165 40
28
©
¹
(3)
ADVANCE INFORMATION
8.6.7 Address 0x06 Humidity MAX
This register implements humidity peak detector function. It stores the highest humidity value converted after the
power up. Value is reset at power up and/or with soft reset procedure.
Table 19. Address 0x06 Humidity MAX Register
7
6
5
4
3
HUMIDITYMAX[7:0]
2
1
0
Table 20. Address 0x06 Humidity MAX Field Descriptions
BIT
FIELD
[7:0]
HUMIDITYMAX[7:0]
TYPE
R/W
RESET
00000000
DESCRIPTION
Stores maximum humidity measurement from all I2C read
requests for humidity
Not supported in Auto Measurement Mode
The humidity can be calculated from the output data with Equation 4:
Humidity (%RH)
20
§ 100 ·
HUMIDITYMAX >7 : 0 @ u ¨ 8 ¸
© 2 ¹
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8.6.8 Address 0x07 Interrupt Configuration
Table 21. Address 0x07 Interrupt Configuration Register
7
DRDY_ENABLE
6
TH_ENABLE
5
TL_ENABLE
4
HH_ENABLE
3
HL_ENABLE
2
RES
1
RES
0
RES
Table 22. Address 0x07 Interrupt Configuration Field Descriptions
FIELD
TYPE
RESET
DESCRIPTION
7
DRDY_ENABLE
R/W
0
DataReady Interrupt enable
0 = DataReady Interrupt generator disable
1 = DataReady Interrupt generator enable
6
TH_ENABLE
R/W
0
Temperature threshold HIGH Interrupt enable
0 = Temperature high Interrupt generator disable
1 = Temperature high Interrupt generator enable
5
TL_ENABLE
R/W
0
Temperature threshold LOW Interrupt enable
0 = Temperature low Interrupt generator disable
1 = Temperature low Interrupt generator enable
4
HH_ENABLE
R/W
0
Humidity threshold HIGH Interrupt enable
0 = Humidity high Interrupt generator disable
1 = Humidity high Interrupt generator enable
3
HL_ENABLE
R/W
0
Humidity threshold LOW Interrupt enable
0 = Humidity low Interrupt generator disable
1 = Humidity low Interrupt generator enable
2
RES
0
Reserved
1
RES
0
Reserved
0
RES
0
Reserved
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BIT
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8.6.9 Address 0x08 Temperature Offset Adjustment
Table 23. Address 0x08 Temperature Offset Adjustment Register
7
6
5
4
3
TEMP_OFFSET_ADJUST[7:0]
2
1
0
Table 24. Address 0x08 Temperature Offset Adjustment Field Descriptions
BIT
FIELD
[7:0]
TYPE
TEMP_OFFSET_ADJUST [7:0]
R/W
RESET
00000000
DESCRIPTION
Temperature offset adjustment. Added to the converted
Temperature value
The temperature can be adjusted adding the following values that are enable settings the equivalents bits:
7
–20.62°C
6
+10.32°C
5
+5.16°C
4
+2.58°C
3
+1.28°C
2
+0.64°C
1
+0.32°C
0
+0.16°C
The value is added to the converted temperature value for offset adjustment as shown in Figure 14.
ADVANCE INFORMATION
Converted Value
+
Temperature Output
User Temperature Offset
Figure 14. Temperature Output Calculation
The resulting temperature offset is a summation of the register bits that have been enabled (that is, programmed
to 1). Some examples:
1. Programming TEMP_OFFSET_ADJUST to 00000001 adjusts the reported temperature by +0.16°C.
2. Programming TEMP_OFFSET_ADJUST to 00000111 adjusts the reported temperature by +1.12°C.
3. Programming TEMP_OFFSET_ADJUST to 00001101 adjusts the reported temperature by +2.08°C.
4. Programming TEMP_OFFSET_ADJUST to 11111111 adjusts the reported temperature by –0.16°C.
5. Programming TEMP_OFFSET_ADJUST to 11111001 adjusts the reported temperature by –1.12°C.
6. Programming TEMP_OFFSET_ADJUST to 11110011 adjusts the reported temperature by –2.08°C.
22
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8.6.10 Address 0x09 Humidity Offset Adjustment
Table 25. Address 0x09 Humidity Offset Adjustment Register
7
6
5
4
3
HUM_OFFSET_ADJUST [7:0]
2
1
0
Table 26. Address 0x09 Humidity Offset Adjustment Field Descriptions
BIT
[7:0]
FIELD
TYPE
HUM_OFFSET_ADJUST [7:0]
R/W
RESET
00000000
DESCRIPTION
Humidity offset adjustment. Added to the converted Humidity
value
The humidity can be adjusted adding the following values that are enable settings the equivalents bits:
7
–25%RH
6
+12.5%RH
5
+6.3%RH
4
+3.1%RH
3
+1.6%RH
2
+0.8%RH
1
+0.4%RH
0
+0.2%RH
Converted Value
+
Humidity Output
User Humidity Offset
Figure 15. Humidity Output Calculation
The resulting humidity offset is a summation of the register bits that have been enabled (that is, programmed to
1). Some examples:
1. Programming HUM_OFFSET_ADJUST to 00000001 adjusts the reported humidity by +0.20%RH.
2. Programming HUM_OFFSET_ADJUST to 00000101 adjusts the reported humidity by +1.00%RH.
3. Programming HUM_OFFSET_ADJUST to 00001010 adjusts the reported humidity by +2.00%RH.
4. Programming HUM_OFFSET_ADJUST to 11111111 adjusts the reported humidity by –0.10%RH.
5. Programming HUM_OFFSET_ADJUST to 11111011 adjusts the reported humidity by –0.90%RH.
6. Programming HUM_OFFSET_ADJUST to 11110101 adjusts the reported humidity by –2.10%RH.
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ADVANCE INFORMATION
The value is added to the converted temperature value for offset adjustment as shown in Figure 15
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8.6.11 Address 0x0A Temperature Threshold LOW
Table 27. Address 0x0A Temperature Threshold LOW Register
7
6
5
4
3
TEMP_THRES_LOW[7:0]
2
1
0
Table 28. Address 0x0A Temperature Threshold LOW Field Descriptions
BIT
FIELD
[7:0]
TYPE
TEMP_THRES_LOW[7:0]
R/W
RESET
00000000
DESCRIPTION
Temperature threshold LOW value
The Temperature Threshold LOW can be calculated from the output data with Equation 5:
Temperature threshold low (qC)
§ TEMP_THRES_LOW [7 : 0] ·
¨
¸ u 165 40
©
¹
28
(5)
8.6.12 Address 0x0B Temperature Threshold HIGH
Table 29. Address 0x0B Temperature Threshold HIGH Register
7
6
5
ADVANCE INFORMATION
4
3
TEMP_THRES_HIGH[7:0]
2
1
0
Table 30. Address 0x0B Temperature Threshold HIGH Field Descriptions
BIT
FIELD
[7:0]
TYPE
TEMP_THRES_HIGH[7:0]
R/W
RESET
11111111
DESCRIPTION
Temperature threshold HIGH value
The Temperature Threshold HIGH can be calculated from the output data with Equation 6:
Temperature threshold high (qC)
§ TEMP_THRES_HIGH [7 : 0] ·
¨
¸ u 165 40
©
¹
28
(6)
8.6.13 Address 0x0C Humidity Threshold LOW
Table 31. Address 0x0C Humidity Threshold LOW Register
7
6
5
4
3
HUMI_THRES_LOW[7:0]
2
1
0
Table 32. Address 0x0C Humidity Threshold LOW Field Descriptions
BIT
FIELD
[7:0]
HUMI_THRES_LOW[7:0]
TYPE
R/W
RESET
00000000
DESCRIPTION
Humidity threshold LOW value
The Humidity Threshold LOW can be calculated from the output data with Equation 7:
Humidity threashold low (%RH)
24
§ HUMI_THRES_LOW [7 : 0] ·
¨
¸ u 100
28
©
¹
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8.6.14 Address 0x0D Humidity Threshold HIGH
Table 33. Address 0x0D Humidity Threshold HIGH Register
7
6
5
4
3
HUMI_THRES_HIGH[7:0]
2
1
0
Table 34. Address 0x0D Humidity Threshold HIGH Field Descriptions
BIT
[7:0]
FIELD
TYPE
HUMI_THRES_HIGH[7:0]
R/W
RESET
11111111
DESCRIPTION
Humidity threshold HIGH value
The Humidity Threshold HIGH can be calculated from the output data with Equation 8:
Humidity threshold high (%RH)
§ HUMI_THRES_HIGH [7 : 0] ·
¨
¸ u 100
©
¹
28
(8)
8.6.15 Address 0x0E Reset and DRDY/INT Configuration Register
Table 35. Address 0x0E Configuration Register
6
AMM[2]
5
AMM[1]
4
AMM[0]
3
HEAT_EN
2
DRDY/INT_EN
1
INT_POL
0
INT_MODE
ADVANCE INFORMATION
7
SOFT_RES
Table 36. Address 0x0E Configuration Field Descriptions
BIT
7
FIELD
TYPE
RESET
DESCRIPTION
SOFT_RES
R/W
0
0 = Normal Operation mode, this bit is self-clear
1 = Soft Reset
EEPROM value reload and registers reset
[6:4]
AMM[2:0]
R/W
000
Configure Auto Measurement Mode (AMM)
000 = Disabled (Trigger-On-Demand Mode)
001 = 1/120Hz (1 samples every 2 minutes)
010 = 1/60Hz (1 samples every minute)
011 = 0.1Hz (1 samples every 10 seconds)
100 = 0.2 Hz (1 samples every 5 second)
101 = 1Hz (1 samples every second)
110 = 2Hz (2 samples every second)
111 = 5Hz (5 samples every second)
3
HEAT_EN
R/W
0
0 = Heater off
1 = Heater on
2
DRDY/INT_EN
R/W
0
DRDY/INT_EN pin configuration
0 = High Z
1 = Enable
1
INT_POL
R/W
0
Interrupt polarity
0 = Active Low
1 = Active High
0
INT_MODE
R/W
0
Interrupt mode
0 = Level sensitive
1 = Comparator mode
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8.6.16 Address 0x0F Measurement Configuration
Table 37. Address 0x0F Measurement Configuration Register
7
TRES[1]
6
TRES[0]
5
HRES[1]
4
HRES[0]
3
RES
2
MEAS_CONF[1]
1
MEAS_CONF[0]
0
MEAS_TRIG
Table 38. Address 0x0F Measurement Configuration Field Descriptions
BIT
FIELD
TYPE
RESET
DESCRIPTION
7:6
TRES[1:0]
R/W
00
Temperature resolution
00: 14 bit
01: 11 bit
10: 9 bit
11: NA
5:4
HRES[1:0]
R/W
00
Humidity resolution
00: 14 bit
01: 11 bit
10: 9 bit
11: NA
RES
R/W
0
Reserved
MEAS_CONF[1:0]
R/W
00
Measurement configuration
00: Humidity + Temperature
01: Temperature only
10: NA
11: NA
MEAS_TRIG
R/W
0
Measurement trigger
0: no action
1: Start measurement
Self-clearing bit when measurement completed
Starts single measurement in Trigger-On-Demand Mode
Starts continuous measurements in Auto Measurement Mode
3
ADVANCE INFORMATION
2:1
0
8.6.17 Manufacturer ID Low
Table 39. Manufacturer ID Low Register
7
6
5
4
3
MANUFACTURER ID[7:0]
2
1
0
Table 40. Address 0xFC Manufacturer ID Low Field Descriptions
BIT
FIELD
[7:0]
TYPE
MANUFACTURER ID [7:0]
R
RESET
01001001
DESCRIPTION
Manufacturer ID LOW value
8.6.18 Manufacturer ID High
These registers contain a factory-programmable identification value that identifies this device as being
manufactured by Texas Instruments. These registers distinguish this device from other devices that are on the
same I2C bus. The manufacturer ID reads 0x4954.
Table 41. Manufacturer ID High Register
7
6
5
4
3
MANUFACTURER ID[15:8]
2
1
0
Table 42. Address 0xFD Manufacturer ID High Field Descriptions
BIT
FIELD
[7:0]
26
MANUFACTURER ID [15:8]
TYPE
R
RESET
01010100
DESCRIPTION
Manufacturer ID HIGH value
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8.6.19 Device ID Low
Table 43. Device ID Low Register
7
6
5
4
3
2
1
0
DEVICE ID[7:0]
Table 44. Address 0xFE Device ID Low Field Descriptions
BIT
FIELD
[7:0]
TYPE
DEVICE ID [7:0]
R
RESET
11010000
DESCRIPTION
Device ID LOW value
8.6.20 Device ID High
These registers contain a factory-programmable identification value that identifies this device as a HDC2021.
These registers distinguish this device from other devices that are on the same I2C bus. The Device ID for the
HDC2021 is 0x07D0.
Table 45. Device ID High Register
6
5
4
3
DEVICE ID[15:8]
2
1
0
ADVANCE INFORMATION
7
Table 46. Address 0xFF Device ID High Field Descriptions
BIT
[7:0]
FIELD
DEVICE ID [15:8]
TYPE
R
RESET
00000111
DESCRIPTION
Device ID HIGH value
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
An HVAC system thermostat control is made up of environmental sensors and a microcontroller. The
microcontroller acquires data from humidity and temperature sensors and controls the heating and cooling
system. The collected data are then shown on a display that can be easily controlled by the microcontroller.
Based on data from the humidity and temperature sensor, the heating and cooling system then maintains the
environment at the customer-defined preferred conditions.
9.2 Typical Application
DISPLAY
TEMPERATURE: 25°C/ 77°F
Relative Humidity (RH): 25%
Red
+
Lithium
Ion Battery
TIME: XX:XX
DATE: XX:XX:XX
1.8 V
VDD
HDC2021
RH
Violet
Sensor
MUX
MUX
ADC
Red
1.8 V
Registers/
Red
Logic
I2 C
Red
Interface
SCL
SDA
INT
MCU
I2C Red
Peripheral
Red
GPIOs
GPIO
ADDR
Temp
Violet
Sensor
VDD
GPIOs
±
Orange
ADVANCE INFORMATION
In a battery-powered HVAC system thermostat, one of the key parameters in the selection of components is the
power consumption. The HDC2021, with a current consumption of 550 nA (the average consumption over 1s for
RH and Temperature measurements), and in conjunction with the MSP430, represents one way an engineer can
obtain low power consumption to extend battery life. A system block diagram of a battery-powered thermostat is
shown in Figure 16.
GND
Calibration
Red
Coefficients
GND
KEYPAD
Button1
C
Button2
C
C
Button3
C
Button4
C
Figure 16. Typical Application Schematic HVAC
28
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Typical Application (continued)
9.2.1 Design Requirements
To improve measurement accuracy, TI recommends to isolate the HDC2021 from all heat sources in the form of
active circuitry, batteries, displays, and resistive elements. If design space is a constraint, cutouts surrounding
the device or the inclusion of small trenches can help minimize heat transfer from PCB heat sources to the
HDC2021. To avoid self-heating the HDC2021, TI recommends to configure the device for a maximum sample
rate of 1 Hz (1 sps).
9.2.2 Detailed Design Procedure
When a circuit board layout is created from the schematic shown in , a small circuit board is possible. The
accuracy of a RH and temperature measurement depends on the sensor accuracy and the setup of the sensing
system. The HDC2021 samples relative humidity and temperature in its immediate environment, it is therefore
important that the local conditions at the sensor match the monitored environment. Use one or more openings in
the physical cover of the thermostat to obtain a good airflow even in static conditions. Refer to the layout
(Figure 18) for a PCB layout that minimizes the thermal mass of the PCB in the region of the HDC2021, which
can improve measurement response time and accuracy.
These results were acquired at TA = 30°C using a humidity chamber that sweeps RH%. The sweep profile used
was 20% > 30% > 40% > 50% > 60% > 70% > 60% > 50% > 40% > 30% > 20%. Each RH% set point was held
for 20 minutes.
Figure 17. RH% Readings of Chamber and HDC2021 vs. Time
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9.2.3 Application Curve
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10 Power Supply Recommendations
The HDC2021 requires a voltage supply within 1.62 V and 3.6 V. TI recommends a multilayer ceramic bypass
X7R capacitor of 0.1 µF between the VDD and GND pins.
11 Layout
11.1 Layout Guidelines
The HDC2021’s relative humidity-sensing element is located on the top side of the package.
TI recommends that the user eliminate the copper layers below the device (GND, VDD) and create slots in the
PCB around the device to enhance the thermal isolation of the HDC2021. To ensure the temperature sensor
performance, TI highly recommends that the user follow the Land Pattern, Solder Mask, and Solder Paste
examples depicted in the Mechanical, Packaging, and Orderable Information.
11.1.1 Guidelines for HDC2021 Storage and PCB Assembly
11.1.1.1 Storage and Handling
ADVANCE INFORMATION
As with all humidity sensors, the HDC2021 must follow special guidelines regarding handling and storage that
are not common with standard semiconductor devices. Long exposure to UV and visible light, or exposure to
chemical vapors for prolonged periods, should be avoided as it may affect RH% accuracy. Additionally, the
device should be protected from out-gassed solvent vapors produced during manufacturing, transport, operation,
and package materials (that is, adhesive tapes, stickers, bubble foils). For further detailed information, see
Humidity Sensor: Storage and Handling Guidelines (SNIA025).
11.1.1.2 Soldering Reflow
For PCB assembly, standard reflow soldering ovens may be used. The HDC2021 uses the standard soldering
profile IPC/JEDEC J-STD-020 with peak temperatures at 260°C. When soldering the HDC2021, it is mandatory
to use no-clean solder paste, and the paste must not be exposed to water or solvent rinses during assembly
because these contaminants may affect sensor accuracy. After reflow, it is expected that the sensor will
generally output a shift in relative humidity, which, once the polyimide tape is peeled off, will reduce over time as
the sensor is exposed to typical indoor ambient conditions. These conditions include 30-40% RH at room
temperature during a duration of several days. Following this rehydration procedure allows the polymer to
correctly settle after reflow and return to the calibrated RH accuracy.
11.1.1.3 Rework
The polyimide tape of the HDC2021 can withstand at least three standard reflow cycles. In the case of tape
removal, TI recommends to limit the HDC2021 to a single IR reflow with no rework, but a second reflow may be
possible if the following guidelines are met:
• The exposed polymer (humidity sensor) is kept clean and undamaged.
• The no-clean solder paste is used and the process is not exposed to any liquids, such as water or solvents.
• The peak soldering temperature does not exceed 260°C.
11.1.1.4 High Temperature and Humidity Exposure
Long exposure outside the recommended operating conditions may temporarily offset the RH output. The
recommended humidity operating range is 20% to 80% RH (non-condensing) over 0°C to 60°C. Prolonged
operation beyond these ranges may shift the sensor reading with a slow recovery time.
11.1.1.5 Bake/Rehydration Procedure
Prolonged exposure to extreme conditions or harsh contaminants may impact sensor performance. In the case
that permanent offset is observed from contaminants, the following procedure is suggested, which may recover
or reduce the error observed in sensor performance:
1. Baking: 100°C, at less than 5%RH, for 5 to 10 hours
2. Rehydration: Between 20°C to 30°C, 60%RH to 75%RH, for 6 to 12 hours
30
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11.2 Layout Example
ADVANCE INFORMATION
The only component next to the device is the supply bypass capacitor. The relative humidity is dependent on the
temperature, so the HDC2021 should be positioned away from hot spots present on the board, such as a battery,
display, or microcontroller. Slots around the device can be used to reduce the thermal mass for a quicker
response to environmental changes. The DAP may be soldered to a floating pad on the board, but the board pad
should NOT be connected to GND
Figure 18. HDC2021 PCB Layout Example
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
For related documentation see the following:
• Texas Instruments, Humidity Sensor: Storage and Handling Guidelines application report (SNIA025)
• Texas Instruments, Optimizing Placement and Routing for Humidity Sensors application report (SNAA297)
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Support Resources
TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight
from the experts. Search existing answers or ask your own question to get the quick design help you need.
ADVANCE INFORMATION
Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do
not necessarily reflect TI's views; see TI's Terms of Use.
12.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
12.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
32
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ADVANCE INFORMATION
34
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PACKAGE OPTION ADDENDUM
www.ti.com
24-Dec-2019
PACKAGING INFORMATION
Orderable Device
Status
(1)
PHDC2021DEBT
ACTIVE
Package Type Package Pins Package
Drawing
Qty
WSON
DEB
6
250
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
TBD
Call TI
Call TI
Op Temp (°C)
Device Marking
(4/5)
-40 to 125
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
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