±0.25°C Accurate, 16-Bit Digital SPI Temperature Sensor ADT7320 Data Sheet

±0.25°C Accurate, 16-Bit Digital SPI Temperature Sensor ADT7320 Data Sheet
±0.25°C Accurate, 16-Bit Digital
SPI Temperature Sensor
ADT7320
Data Sheet
FEATURES
GENERAL DESCRIPTION
High performance
Temperature accuracy
±0.20°C from −10°C to +85°C at 3.0 V
±0.25°C from −20°C to +105°C at 2.7 V to 3.3 V
16-bit temperature resolution: 0.0078°C
Ultralow temperature drift: 0.0073°C
NIST traceable or equivalent
Fast first temperature conversion on power-up of 6 ms
Easy implementation
No temperature calibration/correction required by user
No linearity correction required
Low power
Power saving 1 sample per second (SPS) mode
700 µW typical at 3.3 V in normal mode
7 µW typical at 3.3 V in shutdown mode
Wide operating ranges
Temperature range: −40°C to +150°C
Voltage range: 2.7 V to 5.5 V
Programmable interrupts
Critical overtemperature interrupt
Overtemperature/undertemperature interrupt
SPI-compatible interface
16-lead, RoHS-compliant, 4 mm × 4 mm LFCSP package
The ADT7320 is a high accuracy digital temperature sensor that
offers breakthrough performance over a wide industrial temperature
range, housed in a 4 mm × 4 mm LFCSP package. It contains an
internal band gap reference, a temperature sensor, and a 16-bit
analog-to-digital converter (ADC) to monitor and digitize the
temperature to a resolution of 0.0078°C. The ADC resolution,
by default, is set to 13 bits (0.0625°C). The ADC resolution is a
user programmable mode that can be changed through the
serial interface.
APPLICATIONS
1.
2.
3.
4.
The ADT7320 is guaranteed to operate over supply voltages from
2.7 V to 5.5 V. Operating at 3.3 V, the average supply current is
typically 210 µA. The ADT7320 has a shutdown mode that powers
down the device and offers a shutdown current of typically 2.0 µA
at 3.3 V. The ADT7320 is rated for operation over the −40°C to
+150°C temperature range.
The CT pin is an open-drain output that becomes active when the
temperature exceeds a programmable critical temperature limit.
The INT pin is also an open-drain output that becomes active
when the temperature exceeds a programmable limit. The INT pin
and CT pin can operate in either comparator or interrupt mode.
PRODUCT HIGHLIGHTS
RTD and thermistor replacement
Thermocouple cold junction compensation
Medical equipment
Industrial control and test
Food transportation and storage
Environmental monitoring and HVAC
Laser diode temperature control
5.
Ease of use, no calibration or correction required by the user.
Low power consumption.
Excellent long term stability and reliability.
High accuracy for industrial, instrumentation, and medical
applications.
Packaged in a 16-lead, RoHS-compliant, 4 mm × 4 mm
LFCSP package.
FUNCTIONAL BLOCK DIAGRAM
TEMPERATURE
VALUE
REGISTER
ADT7320
TLOW
REGISTER
TCRIT
REGISTER
STATUS
REGISTER
THIGH
REGISTER
ID
REGISTER
INTERNAL
REFERENCE
10 CT
TCRIT
TEMPERATURE
SENSOR
DIN 3
9 INT
THIGH
SCLK 1
DOUT 2
Σ-Δ
MODULATOR
FILTER
LOGIC
SPI
INTERFACE
TLOW
11 GND
12 VDD
CS 4
09012-001
THYST
REGISTER
CONFIGURATION
REGISTER
INTERNAL
OSCILLATOR
Figure 1.
Rev. 0
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
©2012 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
ADT7320
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Configuration Register .............................................................. 14
Applications ....................................................................................... 1
Temperature Value Register ...................................................... 15
General Description ......................................................................... 1
ID Register................................................................................... 15
Product Highlights ........................................................................... 1
TCRIT Setpoint Register ............................................................... 15
Functional Block Diagram .............................................................. 1
THYST Setpoint Register............................................................... 16
Revision History ............................................................................... 2
THIGH Setpoint Register .............................................................. 16
Specifications..................................................................................... 3
TLOW Setpoint Register ............................................................... 16
SPI Timing Specifications ........................................................... 4
Serial Interface ................................................................................ 17
Absolute Maximum Ratings ............................................................ 5
SPI Command Byte .................................................................... 17
ESD Caution .................................................................................. 5
Writing Data ............................................................................... 18
Pin Configuration and Function Descriptions ............................. 6
Reading Data ............................................................................... 19
Typical Performance Characteristics ............................................. 7
Interfacing to DSPs or Microcontrollers ................................. 19
Theory of Operation ........................................................................ 9
Serial Interface Reset.................................................................. 19
Circuit Information ...................................................................... 9
INT and CT Outputs...................................................................... 20
Converter Details.......................................................................... 9
Undertemperature and Overtemperature Detection ............ 20
Continuous Conversion Mode ................................................... 9
Applications Information .............................................................. 22
One-Shot Mode .......................................................................... 10
Thermal Response Time ........................................................... 22
1 SPS Mode .................................................................................. 11
Supply Decoupling ..................................................................... 22
Shutdown Mode.......................................................................... 11
Powering from a Switching Regulator ..................................... 22
Fault Queue ................................................................................. 11
Temperature Measurement ....................................................... 22
Temperature Data Format ......................................................... 12
Quick Guide to Measuring Temperature ................................ 22
Temperature Conversion Formulas ......................................... 12
Outline Dimensions ....................................................................... 23
Registers ........................................................................................... 13
Ordering Guide .......................................................................... 23
Status Register ............................................................................. 13
REVISION HISTORY
12/12—Revision 0: Initial Version
Rev. 0 | Page 2 of 24
Data Sheet
ADT7320
SPECIFICATIONS
TA = −40°C to +125°C, VDD = 2.7 V to 5.5 V, unless otherwise noted.
Table 1.
Parameter
TEMPERATURE SENSOR AND ADC
Accuracy 1
Min
ADC Resolution
Temperature Resolution
13-Bit
16-Bit
Temperature Conversion Time
Fast Temperature Conversion Time
1 SPS Conversion Time
Temperature Hysteresis 4
Repeatability 5
Drift 6
DC PSRR
DIGITAL OUTPUTS (CT, INT), OPEN DRAIN
High Output Leakage Current, IOH
Output Low Voltage, VOL
Output High Voltage, VOH
Output Capacitance, COUT
DIGITAL INPUTS (DIN, SCLK, CS)
Input Current
Input Low Voltage, VIL
Input High Voltage, VIH
Pin Capacitance
DIGITAL OUTPUT (DOUT)
Output High Voltage, VOH
Output Low Voltage, VOL
Output Capacitance, COUT
POWER REQUIREMENTS
Supply Voltage
Supply Current
At 3.3 V
At 5.5 V
1 SPS Current
At 3.3 V
At 5.5 V
Typ
Max
Unit
Test Conditions/Comments
0.0017
±0.20 2
±0.25
±0.31
±0.35
±0.50
±0.50 3
±0.66
−0.85
−1.0
13
°C
°C
°C
°C
°C
°C
°C
°C
°C
Bits
16
Bits
TA = −10°C to +85°C, VDD = 3.0 V
TA = −20°C to +105°C, VDD = 2.7 V to 3.3 V
TA = −40°C to +105°C, VDD = 3.0 V
TA = −40°C to +105°C, VDD = 2.7 V to 3.3 V
TA = −40°C to +125°C, VDD = 2.7 V to 3.3 V
TA = −10°C to +105°C, VDD = 4.5 V to 5.5 V
TA = −40°C to +125°C, VDD = 4.5 V to 5.5 V
TA = +150°C, VDD = 4.5 V to 5.5 V
TA = +150°C, VDD = 2.7 V to 3.3 V
Twos complement temperature value of sign bit plus
12 ADC bits (power-up default resolution)
Twos complement temperature value of sign bit plus
15 ADC bits (Bit 7 = 1 in the configuration register)
0.0625
0.0078
240
6
60
±0.002
±0.015
0.0073
0.1
°C
°C
ms
ms
ms
°C
°C
°C
°C/V
13-bit resolution (sign + 12 bits)
16-bit resolution (sign + 15 bits)
Continuous conversion and one-shot conversion mode
First conversion on power-up only
Conversion time for 1 SPS mode
Temperature cycle = 25°C to 125°C and back to 25°C
TA = 25°C
500 hour stress test at 150°C with VDD = 5.0 V
TA = 25°C
5
0.4
µA
V
V
pF
CT and INT pins pulled up to 5.5 V
IOL = 3 mA at 5.5 V, IOL = 1 mA at 3.3 V
±1
0.4
VIN = 0 V to VDD
10
µA
V
V
pF
0.4
50
V
V
pF
ISOURCE = ISINK = 200 µA
IOL = 200 µA
5.5
V
265
300
µA
µA
0.1
0.7 × VDD
2
0.7 × VDD
5
VDD − 0.3
2.7
Peak current while converting, SPI interface inactive
210
250
46
65
µA
µA
Rev. 0 | Page 3 of 24
1 SPS mode, TA = 25°C
VDD = 3.3 V
VDD = 5.5 V
ADT7320
Data Sheet
Parameter
Shutdown Current
At 3.3 V
At 5.5 V
Power Dissipation, Normal Mode
Power Dissipation, 1 SPS Mode
Min
Typ
Max
Unit
2.0
5.2
700
150
15
25
µA
µA
µW
µW
Test Conditions/Comments
Supply current in shutdown mode
VDD = 3.3 V, normal mode at 25°C
Power dissipated for VDD = 3.3 V, TA = 25°C
Accuracy specification includes repeatability.
The equivalent 3 σ limits are ±0.15°C. This 3 σ specification is provided to enable comparison with other vendors who use these limits.
For higher accuracy at 5 V operation, contact Analog Devices, Inc.
4
Temperature hysteresis does not include repeatability.
5
Based on a floating average of 10 readings.
6
Drift includes solder heat resistance and lifetime test performed as per JEDEC Standard JESD22-A108.
1
2
3
SPI TIMING SPECIFICATIONS
TA = −40°C to +150°C, VDD = 2.7 V to 5.5 V, unless otherwise noted. All input signals are specified with rise time (tR) = fall time (tF) = 5 ns
(10% to 90% of VDD) and timed from a voltage level of 1.6 V.
Table 2.
Parameter 1, 2
Limit at TMIN, TMAX
Unit
Descriptions
t1
t2
t3
t4
t5
t6
0
100
100
30
25
5
60
80
10
80
0
0
60
80
10
ns min
ns min
ns min
ns min
ns min
ns min
ns max
ns max
ns min
ns max
ns min
ns min
ns max
ns max
ns min
CS falling edge to SCLK active edge setup time
SCLK high pulse width
SCLK low pulse width
Data setup time prior to SCLK rising edge
Data hold time after SCLK rising edge
Data access time after SCLK falling edge
VDD = 4.5 V to 5.5 V
VDD = 2.7 V to 3.6 V
Bus relinquish time after CS inactive edge
Bus relinquish time after CS inactive edge
SCLK inactive edge to CS rising edge hold time
CS falling edge to DOUT active time
VDD = 4.5 V to 5.5 V
VDD = 2.7 V to 3.6 V
SCLK inactive edge to DOUT low
t7 3
t8
t9
t10
Sample tested during initial release to ensure compliance.
See Figure 2.
3
This means that the times quoted in the timing characteristics in Table 2 are the true bus relinquish times of the part and, as such, are independent of external bus
loading capacitances.
1
2
CS
t1
t2
1
SCLK
t8
t3
2
3
6
7
8
9
10
23
24
t4
t5
DIN
LSB
t6
t9
DOUT
MSB
t10
LSB
t7
Figure 2. Detailed SPI Timing Diagram
Rev. 0 | Page 4 of 24
09012-002
MSB
Data Sheet
ADT7320
ABSOLUTE MAXIMUM RATINGS
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Table 3.
Parameter
VDD to GND
DIN Input Voltage to GND
DOUT Voltage to GND
SCLK Input Voltage to GND
CS Input Voltage to GND
CT and INT Output Voltage to GND
ESD Rating (Human Body Model)
Operating Temperature Range 1
Storage Temperature Range
Maximum Junction Temperature, TJMAX
Power Dissipation 2
16-Lead LFCSP 3
Thermal Impedance 4
θJA, Junction-to-Ambient (Still Air)
θJC, Junction-to-Case
IR Reflow Soldering
Peak Temperature (RoHS-Compliant
Package)
Time at Peak Temperature
Ramp-Up Rate
Ramp-Down Rate
Time from 25°C to Peak Temperature
Rating
−0.3 V to +7 V
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
2.0 kV
−40°C to +150°C
−65°C to +160°C
150°C
ESD CAUTION
WMAX = (TJMAX − TA)/θJA
37°C/W
33°C/W
220°C
260°C (0°C/−5°C)
20 sec to 40 sec
3°C/sec maximum
−6°C/sec maximum
8 minutes maximum
1
Sustained operation above 125°C results in a shorter product lifetime. For
more information, contact an Analog Devices, Inc., sales representative.
2
Values relate to package being used on a standard 2-layer PCB. This gives a
worst-case θJA and θJC.
3
TA = ambient temperature.
4
Junction-to-case resistance is applicable to components featuring a
preferential flow direction, for example, components mounted on a heat
sink. Junction-to-ambient resistance is more useful for air cooled, PCBmounted components.
Rev. 0 | Page 5 of 24
ADT7320
Data Sheet
13 NC
14 NC
15 NC
16 NC
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
17 EPAD
SCLK 1
12 VDD
ADT7320
DOUT 2
10 CT
9 INT
NC 8
NC 7
NC 6
NC 5
CS 4
NOTES
1. NC = NO CONNECT. DO NOT CONNECT TO THIS PIN.
THE NC PIN IS NOT BONDED TO THE DIE INTERNALLY.
2. TO ENSURE CORRECT OPERATION, THE EXPOSED PAD
SHOULD EITHER BE LEFT FLOATING OR CONNECTED
TO GROUND.
09012-003
DIN 3
11 GND
TOP VIEW
(Not to Scale)
Figure 3. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
1
2
3
Mnemonic
SCLK
DOUT
DIN
4
5
6
7
8
9
CS
NC
NC
NC
NC
INT
10
CT
11
12
13
14
15
16
17
GND
VDD
NC
NC
NC
NC
EPAD
Description
Serial Clock Input. The serial clock is used to clock data into and out of any register of the ADT7320.
Serial Data Output. Data is clocked out on the SCLK falling edge and is valid on the SCLK rising edge.
Serial Data Input. Serial data to be loaded to the control registers of the part is provided on this input. Data is
clocked into the registers on the rising edge of SCLK.
Chip Select Input. The device is enabled when this input is low. The device is disabled when this pin is high.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
Overtemperature and Undertemperature Interrupt. Logic output. Power-up default setting is as an active low
comparator interrupt. Open-drain configuration. A pull-up resistor is required, typically 10 kΩ.
Critical Overtemperature Interrupt. Logic output. Power-up default polarity is active low. Open-drain
configuration. A pull-up resistor is required, typically 10 kΩ.
Analog and Digital Ground.
Positive Supply Voltage (2.7 V to 5.5 V). Decouple the supply with a 0.1 μF ceramic capacitor to GND.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
No Connect. Do not connect to this pin. The NC pin is not bonded to the die internally.
Exposed Pad. To ensure correct operation, the exposed pad should either be left floating or connected to ground.
Rev. 0 | Page 6 of 24
Data Sheet
ADT7320
TYPICAL PERFORMANCE CHARACTERISTICS
30
1.00
25
0.50
SHUTDOWN IDD (µA)
MAX ACCURACY LIMITS
0.25
0
–0.25
MAX ACCURACY LIMITS
20
15
10
5.0V
4.5V
3.3V
3.0V
2.7V
3.6V
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
100
120
140
0
–100
09012-027
–1.00
–60
–50
0
50
100
150
200
TEMPERATURE (°C)
09012-032
5
–0.75
Figure 7. Shutdown Current vs. Temperature
Figure 4. Temperature Accuracy at 3 V
300
1.00
0.75
0.50
CONTINUOUS CONVERSION
250
MAX ACCURACY LIMITS
200
0.25
IDD (µA)
0
–0.25
150
100
–0.50
1SPS
MAX ACCURACY LIMITS
50
–0.75
–40
–20
0
20
40
60
80
TEMPERATURE (°C)
100
120
140
0
2.5
09012-026
–1.00
–60
3.5
4.0
4.5
5.0
5.5
6.0
SUPPLY VOLTAGE (V)
Figure 5. Temperature Accuracy at 5 V
Figure 8. Average Operating Supply Current vs. Supply Voltage
8
300
5.5V CONTINUOUS
CONVERSION
250
7
6
SHUTDOWN IDD (µA)
3.0V CONTINUOUS
CONVERSION
200
150
100
0
–100
–50
0
5
4
3
5.5V 1SPS
2
3.0V 1SPS
1
50
50
100
150
TEMPERATURE (°C)
200
09012-028
IDD (µA)
3.0
09012-029
TEMPERATURE ERROR (°C)
5.5V
–0.50
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
Figure 9. Shutdown Current vs. Supply Voltage
Figure 6. Operating Supply Current vs. Temperature
Rev. 0 | Page 7 of 24
6.0
09012-210
TEMPERATURE ERROR (°C)
0.75
ADT7320
Data Sheet
140
125°C
120
85°C
80
IT TAKES LESS THAN 2 SECONDS
FOR THE DUT TO REACH 63.2%
OF ITS FINAL TEMPERATURE SPAN
60
40
20
0
0
5
10
15
TIME (s)
20
25
09012-110
DUT TEMPERATURE (°C)
105°C
100
Figure 10. Thermal Response Time
Rev. 0 | Page 8 of 24
Data Sheet
ADT7320
THEORY OF OPERATION
CIRCUIT INFORMATION
The ADT7320 is a high accuracy digital temperature sensor that
uses a 16-bit ADC to monitor and digitize the temperature to a
resolution of 0.0078°C. By default, the ADC resolution is set to
13 bits (0.0625°C). An internal temperature sensor generates a
voltage proportional to absolute temperature; this voltage is
compared to an internal voltage reference and input into a
precision digital modulator.
The internal temperature sensor has high accuracy and linearity
over the entire rated temperature range without the need for
correction or calibration by the user.
The sensor output is digitized by a sigma-delta (Σ-Δ) modulator,
also known as the charge balance type ADC. This type of converter
uses time domain oversampling and a high accuracy comparator to
deliver 16 bits of resolution in an extremely compact circuit.
CONVERTER DETAILS
The Σ-Δ modulator consists of an input sampler, a summing
network, an integrator, a comparator, and a 1-bit digital-to-analog
converter (DAC). This architecture creates a negative feedback
loop and minimizes the integrator output by changing the duty
cycle of the comparator output in response to the input voltage
changes. The comparator samples the output of the integrator at
a much higher rate than the input sampling frequency. This
oversampling spreads the quantization noise over a much wider
band than that of the input signal, improving overall noise
performance and increasing accuracy.
The ADT7320 can be configured to operate in any one of the
following four operating modes: normal mode, one-shot mode,
1 SPS mode, and shutdown mode.
CONTINUOUS CONVERSION MODE
In continuous conversion mode (default power-up mode), the
ADT7320 runs an automatic conversion sequence. During this
automatic conversion sequence, a conversion takes 240 ms to
complete and the ADT7320 is continuously converting. This means
that as soon as one temperature conversion is completed, another
temperature conversion begins. Each temperature conversion
result is stored in the temperature value register and is available
through the SPI interface. In continuous conversion mode, the
read operation provides the most recent converted result.
On power-up, the first conversion is a fast conversion, taking
typically 6 ms. If the temperature exceeds 147°C, the CT pin is
asserted low. If the temperature exceeds 64°C, the INT pin is
asserted low. Fast conversion temperature accuracy is typically
within ±5°C.
The conversion clock for the part is generated internally. No
external clock is required except when reading from and writing
to the serial port.
The measured temperature value is compared with a critical
temperature limit (stored in the 16-bit TCRIT setpoint register), a
high temperature limit (stored in the 16-bit THIGH setpoint
register), and a low temperature limit (stored in the 16-bit TLOW
setpoint register). If the measured value exceeds the high or low
temperature limits, the INT pin is activated; if it exceeds the TCRIT
limit, the CT pin is activated. The polarity of the INT and CT
pins is programmable for via the configuration register, and the
INT and CT pins are also programmable for interrupt mode via
the configuration register.
The modulated output of the comparator is encoded using a
circuit technique that results in SPI temperature data.
Σ-∆ MODULATOR
INTEGRATOR
COMPARATOR
VOLTAGE
REFERENCE
1-BIT
DAC
CLOCK
GENERATOR
LPF DIGITAL
FILTER
TEMPERATURE
VALUE
REGISTER
13-/16-BIT
09012-012
1-BIT
Figure 11. Σ-∆ Modulator
Rev. 0 | Page 9 of 24
ADT7320
Data Sheet
CS
0x08
DIN
0x20
WAIT 240ms MINIMUM
FOR CONVERSION TO FINISH
DATA
09012-300
DOUT
SCLK
Figure 12. Typical SPI One-Shot Write to Configuration Register Followed by a Read from the Temperature Value Register
TEMPERATURE
149°C
148°C
TCRIT
147°C
146°C
145°C
144°C
143°C
TCRIT – THYST
142°C
141°C
140°C
CT PIN
POLARITY = ACTIVE LOW
CT PIN
POLARITY = ACTIVE HIGH
TIME
WRITE TO
BIT 5 AND BIT 6 OF
CONFIGURATION
REGISTER.*
WRITE TO
BIT 5 AND BIT 6 OF
CONFIGURATION
REGISTER.*
*THERE IS A 240ms DELAY BETWEEN WRITING TO THE CONFIGURATION REGISTER TO START
A STANDARD ONE-SHOT CONVERSION AND THE CT PIN GOING ACTIVE. THIS IS DUE TO THE
CONVERSION TIME. THE DELAY IS 60ms IN THE CASE OF A ONE-SHOT CONVERSION.
09012-013
WRITE TO
BIT 5 AND BIT 6 OF
CONFIGURATION
REGISTER.*
Figure 13. One-Shot CT Pin
ONE-SHOT MODE
CT and INT Operation in One-Shot Mode
When one-shot mode is enabled, the ADT7320 immediately
completes a conversion and then goes into shutdown mode. The
one-shot mode is useful when one of the circuit design priorities is
to reduce power consumption.
See Figure 13 for more information on one-shot CT pin
operation for TCRIT overtemperature events when one of the
limits is exceeded. Note that in interrupt mode, a read from
any register resets the INT and CT pins.
To enable one-shot mode, set Bits [6:5] of the configuration
register (Register Address 0x01) to 01.
For the INT pin in comparator mode, if the temperature drops
below the THIGH − THYST value or goes above the TLOW + THYST value,
a write to the operation mode bits (Bit 5 and Bit 6 of the
configuration register, Register Address 0x01) resets the INT pin.
After writing to the operation mode bits, wait for at least 240 ms
before reading back the temperature from the temperature value
register. This delay ensures that the ADT7320 has adequate time
to power up and complete a conversion.
To obtain an updated temperature conversion, reset Bits[6:5] of the
configuration register (Register Address 0x01) to 01.
For the CT pin in comparator mode, if the temperature drops
below the TCRIT − THYST value, a write to the operation mode bits
(Bit 5 and Bit 6 of the configuration register, Register Address 0x01)
resets the CT pin (see Figure 13).
When using one-shot mode, ensure that the refresh rate is
appropriate to the application being used.
Rev. 0 | Page 10 of 24
Data Sheet
ADT7320
1 SPS MODE
FAULT QUEUE
In 1 SPS mode, the part performs one measurement per second.
A conversion takes 60 ms typically, and the part remains in the
idle state for the remaining 940 ms period. This mode is
enabled by setting Bits[6:5] of the configuration register
(Register Address 0x01) to 10.
Bit 0 and Bit 1 of the configuration register (Register Address 0x01)
are used to set up a fault queue. Up to four faults are provided to
prevent false tripping of the INT and CT pins when the ADT7320
is used in a noisy temperature environment. The number of
faults set in the queue must occur consecutively to set the INT
and CT outputs. For example, if the number of faults set in the
queue is four, then four consecutive temperature conversions
must occur, with each result exceeding a temperature limit set in
any of the limit registers, before the INT and CT pins are activated.
If two consecutive temperature conversions exceed a temperature
limit and the third conversion does not, the fault count is reset to
zero.
SHUTDOWN MODE
The ADT7320 can be placed in shutdown mode by setting
Bits[6:5] of the configuration register (Register Address 0x01) to
11. The ADT7320 can be taken out of shutdown mode by
setting Bits[6:5] of the configuration register (Register Address
0x01) to 00. The ADT7320 typically takes 1 ms (with a 0.1 μF
decoupling capacitor) to come out of shut-down mode. The
conversion result from the last conversion prior to shutdown
can still be read from the ADT7320 even when it is in shutdown
mode. When the part is taken out of shutdown mode, the
internal clock restarts and a conversion is initiated.
Rev. 0 | Page 11 of 24
ADT7320
Data Sheet
TEMPERATURE DATA FORMAT
TEMPERATURE CONVERSION FORMULAS
One LSB of the ADC corresponds to 0.0625°C in 13-bit mode or
0.0078°C in 16-bit mode. The ADC can theoretically measure a
temperature range of 255°C, but the ADT7320 is guaranteed to
measure a low value temperature limit of −40°C to a high value
temperature limit of +150°C. The temperature measurement
result is stored in the 16-bit temperature value register and is
compared with the high temperature limits stored in the TCRIT
setpoint register and the THIGH setpoint register. It is also compared
with the low temperature limit stored in the TLOW setpoint register.
16-Bit Temperature Data Format
Temperature data in the temperature value register, the TCRIT
setpoint register, the THIGH setpoint register, and the TLOW
setpoint register are represented by a 13-bit, twos complement
word. The MSB is the temperature sign bit. On power-up the three
LSBs, Bit 0 to Bit 2, are not part of the temperature conversion
result and are flag bits for TCRIT, THIGH, and TLOW. Table 5 shows
the 13-bit temperature data format without Bit 0 to Bit 2.
The number of bits in the temperature data-word can be extended
to 16 bits, twos complement by setting Bit 7 to 1 in the configuration
register (Register Address 0x01). When using a 16-bit temperature
data value, Bit 0 to Bit 2 are not used as flag bits and are instead
the LSB bits of the temperature value. The power-on default
setting has a 13-bit temperature data value.
Reading back the temperature from the temperature value register
requires a 2-byte read. Designers that use a 9-bit temperature
data format can still use the ADT7320 by ignoring the last four
LSBs of the 13-bit temperature value. These four LSBs are Bit 3
to Bit 6 in Table 5.
Positive Temperature = ADC Code (dec)/128
Negative Temperature = (ADC Code (dec) − 65,536)/128
where ADC Code uses all 16 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code (dec) − 32,768)/128
where the MSB is removed from the ADC code.
13-Bit Temperature Data Format
Positive Temperature = ADC Code (dec)/16
Negative Temperature = (ADC Code (dec) − 8192)/16
where ADC Code uses all 13 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code (dec) − 4096)/16
where the MSB is removed from the ADC code.
10-Bit Temperature Data Format
Positive Temperature = ADC Code (dec)/2
Negative Temperature = (ADC Code (dec) − 1024)/2
where ADC Code uses all 10 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code (dec) − 512)/2
where the MSB is removed from the ADC Code.
9-Bit Temperature Data Format
Table 5. 13-Bit Temperature Data Format
Temperature
−40°C
−25°C
−0.0625°C
0°C
+0.0625°C
+25°C
+105°C
+125°C
+150°C
Digital Output (Binary) Bits[15:3]
1 1101 1000 0000
1 1110 0111 0000
1 1111 1111 1111
0 0000 0000 0000
0 0000 0000 0001
0 0001 1001 0000
0 0110 1001 0000
0 0111 1101 0000
0 1001 0110 0000
Positive Temperature = ADC Code (dec)
Negative Temperature = ADC Code (dec) − 512
where ADC Code uses all nine bits of the data byte, including
the sign bit.
Negative Temperature = ADC Code (dec) − 256
where the MSB is removed from the ADC Code.
Rev. 0 | Page 12 of 24
Data Sheet
ADT7320
REGISTERS
STATUS REGISTER
The ADT7320 contains eight registers:
•
•
•
•
A status register
A configuration register
Five temperature registers
An ID register
The status register, temperature value register, and the ID
register are read only.
Table 6. ADT7320 Registers
Register Address
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
Description
Status
Configuration
Temperature value
ID
TCRIT setpoint
THYST setpoint
THIGH setpoint
TLOW setpoint
Power-On Default
0x80
0x00
0x0000
0xC3
0x4980 (147°C)
0x05 (5°C)
0x2000 (64°C)
0x0500 (10°C)
This 8-bit read-only register (Register Address 0x00) reflects the
status of the overtemperature and undertemperature interrupts
that can cause the CT and INT pins to become active. It also
reflects the status of a temperature conversion operation. The
interrupt flags in this register are reset by a read operation to
the status register and/or when the temperature value returns
within the temperature limits including hysteresis. The RDY bit is
reset after a read from the temperature value register. In oneshot and 1 SPS modes, the RDY bit is reset after a write to the
operation mode bits in the configuration register.
Table 7. Status Register (Register Address 0x00)
Bit(s)
[3:0]
[4]
Default
Value
0000
0
Type
R
R
Name
Unused
TLOW
[5]
0
R
THIGH
[6]
0
R
TCRIT
[7]
1
R
RDY
Description
Reads back 0.
This bit is set to 1 when the temperature goes below the TLOW temperature limit. The bit is cleared to
0 when the status register is read and/or when the temperature measured rises above the limit set
in the TLOW + THYST setpoint registers.
This bit is set to 1 when the temperature rises above the THIGH temperature limit. This bit is cleared
to 0 when the status register is read and/or when the temperature measured drops below the limit
set in the THIGH − THYST setpoint registers.
This bit is set to 1 when the temperature rises above the TCRIT temperature limit. This bit is cleared to
0 when the status register is read and/or when the temperature measured drops below the limit set
in the TCRIT − THYST setpoint registers.
This bit goes low when the temperature conversion result is written to the temperature value
register. It is reset to 1 when the temperature value register is read. In one-shot and 1 SPS modes,
this bit is reset after a write to the operation mode bits in the configuration register.
Rev. 0 | Page 13 of 24
ADT7320
Data Sheet
CONFIGURATION REGISTER
This 8-bit read/write register (Register Address 0x01) stores various
configuration modes for the ADT7320, including shutdown,
overtemperature and undertemperature interrupts, one-shot,
continuous conversion, interrupt pin polarity, and
overtemperature fault queues.
Table 8. Configuration Register (Register Address 0x01)
Bit(s)
[1:0]
Default
Value
00
Type
R/W
Name
Fault queue
[2]
0
R/W
CT pin polarity
[3]
0
R/W
INT pin polarity
[4]
0
R/W
INT/CT mode
[6:5]
00
R/W
Operation mode
[7]
0
R/W
Resolution
Description
These two bits set the number of undertemperature/overtemperature faults that can
occur before setting the INT and CT pins. This helps to avoid false triggering due to
temperature noise.
00 = 1 fault (default).
01 = 2 faults.
10 = 3 faults.
11 = 4 faults.
This bit selects the output polarity of the CT pin.
0 = active low.
1 = active high.
This bit selects the output polarity of the INT pin.
0 = active low.
1 = active high.
This bit selects comparator mode or interrupt mode.
0 = interrupt mode.
1 = comparator mode.
These two bits set the operational mode of the ADT7320.
00 = continuous conversion (default). When one conversion is finished, the ADT7320
begins the next conversion.
01 = one-shot mode. Conversion time is typically 240 ms.
10 = 1 SPS mode. Conversion time is typically 60 ms. This operational mode reduces the
average current consumption.
11 = shutdown. All circuitry except for the interface circuitry is powered down.
This bit sets the resolution of the ADC when converting.
0 = 13-bit resolution. Sign bit + 12 bits gives a temperature resolution of 0.0625°C.
1 = 16-bit resolution. Sign bit + 15 bits gives a temperature resolution of 0.0078°C.
Rev. 0 | Page 14 of 24
Data Sheet
ADT7320
TEMPERATURE VALUE REGISTER
ID REGISTER
The temperature value register stores the temperature measured
by the internal temperature sensor. The temperature is stored in
a 16-bit, twos complement format. The temperature is read back
from the temperature value register (Register Address 0x02) as a
16-bit value.
This 8-bit read-only register (Register Address 0x03) stores
the manufacturer ID in Bit 7 to Bit 3 and the silicon revision in
Bit 2 to Bit 0. The default setting for the ID register is 0xC3.
Bit 2, Bit 1, and Bit 0 are event alarm flags for TCRIT, THIGH, and
TLOW, respectively. When the ADC is configured to convert the
temperature to a 16-bit digital value, Bit 2, Bit 1, and Bit 0 are
no longer used as flag bits and are, instead, used as the LSB bits for
the extended digital value.
TCRIT SETPOINT REGISTER
The 16-bit TCRIT setpoint register (Register Address 0x04) stores
the critical overtemperature limit value. A critical overtemperature
event occurs when the temperature value stored in the temperature
value register exceeds the value stored in this register. The CT
pin is activated if a critical overtemperature event occurs. The
temperature is stored in twos complement format with the MSB
being the temperature sign bit.
The default setting for the TCRIT setpoint is 147°C.
Table 9. Temperature Value Register (Register Address 0x02)
Bit(s)
[0]
Default Value
0
Type
R
Name
TLOW flag/LSB0
[1]
0
R
THIGH flag/LSB1
[2]
0
R
TCRIT flag/LSB2
[7:3]
[14:8]
15
00000
0000000
0
R
R
R
Temp
Temp
Sign
Description
Flags a TLOW event if the configuration register, Register Address 0x01[7] = 0
(13-bit resolution). When the temperature value is below TLOW, this bit is set to 1.
Contains Least Significant Bit 0 of the 15-bit temperature value when the
configuration register, Register Address 0x01[7] = 1 (16-bit resolution).
Flags a THIGH event if the configuration register, Register Address 0x01[7] = 0
(13-bit resolution). When the temperature value is above THIGH, this bit is set to 1.
Contains Least Significant Bit 1 of the 15-bit temperature value when the
configuration register, Register Address 0x01[7] = 1 (16-bit resolution).
Flags a TCRIT event if the configuration register, Register Address 0x01[7] = 0
(13-bit resolution). When the temperature value exceeds TCRIT, this bit is set to 1.
Contains the Least Significant Bit 2 of the 15-bit temperature value if the
configuration register, Register Address 0x01[7] = 1 (16-bit resolution).
Temperature value in twos complement format.
Temperature value in twos complement format.
Sign bit; indicates if the temperature value is negative or positive.
Table 10. ID Register (Register Address 0x03)
Bit(s)
[2:0]
[7:3]
Default Value
011
11000
Type
R
R
Name
Revision ID
Manufacturer ID
Description
Contains the silicon revision identification number.
Contains the manufacturer identification number.
Table 11. TCRIT Setpoint Register (Register Address 0x04)
Bit(s)
[15:0]
Default Value
0x4980
Type
R/W
Name
TCRIT
Description
16-bit critical overtemperature limit, stored in twos complement format.
Rev. 0 | Page 15 of 24
ADT7320
Data Sheet
THYST SETPOINT REGISTER
TLOW SETPOINT REGISTER
The 8-bit THYST setpoint register (Register Address 0x05) stores
the temperature hysteresis value for the THIGH, TLOW, and TCRIT
temperature limits. The temperature hysteresis value is stored in
straight binary format using the four LSBs. Increments are possible
in steps of 1°C from 0°C to 15°C. The value in this register is
subtracted from the THIGH and TCRIT values and added to the
TLOW value to implement hysteresis.
The 16-bit TLOW setpoint register (Register Address 0x07) stores
the undertemperature limit value. An undertemperature event
occurs when the temperature value stored in the temperature
value register is less than the value stored in this register. The
INT pin is activated if an undertemperature event occurs. The
temperature is stored in twos complement format with the MSB
being the temperature sign bit.
The default setting for the THYST setpoint is 5°C.
The default setting for the TLOW setpoint is 10°C.
THIGH SETPOINT REGISTER
The 16-bit THIGH setpoint register (Register Address 0x06) stores
the overtemperature limit value. An overtemperature event occurs
when the temperature value stored in the temperature value
register exceeds the value stored in this register. The INT pin is
activated if an overtemperature event occurs. The temperature
is stored in twos complement format with the most significant
bit being the temperature sign bit.
The default setting for the THIGH setpoint is 64°C.
Table 12. THYST Setpoint Register (Register Address 0x05)
Bit(s)
[3:0]
Default Value
0101
Type
R/W
Name
THYST
Description
Hysteresis value, from 0°C to 15°C. Stored in straight binary format. The default setting is 5°C.
[7:4]
0000
R/W
N/A
N/A = not applicable. Not used.
Table 13. THIGH Setpoint Register (Register Address 0x06)
Bit(s)
[15:0]
Default Value
0x2000
Type
R/W
Name
THIGH
Description
16-bit overtemperature limit, stored in twos complement format.
Table 14. TLOW Setpoint Register (Register Address 0x07)
Bit(s)
[15:0]
Default Value
0x0500
Type
R/W
Name
TLOW
Description
16-bit undertemperature limit, stored in twos complement format.
Rev. 0 | Page 16 of 24
Data Sheet
ADT7320
SERIAL INTERFACE
PULL-UP
TO VDD
VDD
VDD
ADT7320
SCLK
DOUT
DIN
CS
10kΩ
GND
CT
INT
09012-014
MICROCONTROLLER
10kΩ
0.1µF
Figure 14. Typical SPI Interface Connection
The ADT7320 has a 4-wire serial peripheral interface (SPI). The
interface has a data input pin (DIN) for writing data to the device, a
data output pin (DOUT) for reading data back from the device,
and a serial data clock pin (SCLK) for clocking data into and out of
the device. A chip select pin (CS) enables or disables the serial
interface. CS is required for correct operation of the interface.
Data is clocked out of the ADT7320 on the falling edge of SCLK,
and data is clocked into the device on the rising edge of SCLK.
Bit C7, Bit C2, Bit C1, and Bit C0 of the command byte must all be
set to 0 to successfully begin a bus transaction. The SPI interface
does not work correctly if a 1 is written into any of these bits.
Bit C6 is the read/write bit; 1 indicates a read, and 0 indicates
a write.
Bits[C5:C3] contain the target register address. One register can
be read from or written to per bus transaction.
SPI COMMAND BYTE
All data transactions on the bus begin with the master taking
CS from high to low and sending out the command byte. The
command byte indicates to the ADT7320 whether the transaction
is a read or a write and provides the address of the register for the
data transfer. Table 15 shows the command byte.
Table 15. Command Byte
C7
0
C6
R/W
C5
C4
C3
Register address
C2
0
C1
0
C0
0
Rev. 0 | Page 17 of 24
ADT7320
Data Sheet
Figure 15 shows a write to an 8-bit register, and Figure 16 shows
a write to a 16-bit register.
WRITING DATA
Data is written to the ADT7320 in 8 bits or 16 bits, depending on
the addressed register. The first byte written to the device is the
command byte, with the read/write bit set to 0. The master
then supplies the 8-bit or 16-bit input data on the DIN line.
The ADT7320 clocks the data into the register addressed in the
command byte on the rising edge of SCLK. The master finishes
the write transaction by pulling CS high.
The master must begin a new write transaction on the bus for
every register write. Only one register is written to per bus
transaction.
CS
1
2
3
4
5
6
7
8
9
10
11
C7
DIN
R/W
REGISTER ADDR
C6
C4
C5
C3
13
14
15
16
8-BIT DATA
8-BIT COMMAND BYTE
0
12
0
0
0
C2
C1
C0
D7
D6
D5
D4
D3
D2
D1
09012-128
SCLK
D0
Figure 15. Writing to an 8-Bit Register
CS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
DIN
R/W
C7
C6
REGISTER ADDR
C5
C4
C3
16
17
22
23
24
16-BIT DATA
8-BIT COMMAND BYTE
0
15
0
0
0
C2
C1
C0
D15
D14
D13
D12
D11
D10
Figure 16. Writing to a 16-Bit Register
Rev. 0 | Page 18 of 24
D9
D8
D7
D2
D1
D0
09012-129
SCLK
Data Sheet
ADT7320
CS
SCLK
2
1
4
3
5
7
6
9
8
11
10
12
13
14
16
15
8-BIT COMMAND BYTE
DIN
0
R/W
C7
C6
REGISTER ADDR
C5
C4
C3
0
0
0
C2
C1
C0
D7
D6
D5
D4
D3
D2
15
16
17
D1
09012-030
8-BIT DATA
DOUT
D0
Figure 17. Reading from an 8-Bit Register
CS
SCLK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
22
23
24
8-BIT COMMAND BYTE
DIN
0
R/W
C7
C6
REGISTER ADDR
0
0
0
C4
C2
C1
C0
C5
C3
DOUT
D15
D14
D13
D12
D11
D10
D9
D8
D7
D2
D1
D0
09012-031
16-BIT DATA
Figure 18. Reading from a 16-Bit Register
READING DATA
A read transaction begins when the master writes the command
byte to the ADT7320 with the read/write bit set to 1. The master
then supplies 8 or 16 clock pulses, depending on the addressed
register, and the ADT7320 clocks out data from the addressed
register on the DOUT line. Data is clocked out on the first
falling edge of SCLK following the command byte.
The read transaction finishes when the master pulls CS high.
INTERFACING TO DSPs OR MICROCONTROLLERS
The ADT7320 can be operated with CS used as a frame
synchronization signal. This setup is useful for DSP interfaces. In
this case, the first bit (MSB) is effectively clocked out by CS
because CS normally occurs after the falling edge of SCLK in
DSPs. SCLK can continue to run between data transfers, provided
that the timing values are obeyed.
CS can be tied to ground and the serial interface can operate in
a 3-wire mode. DIN, DOUT, and SCLK are used to communicate
with the ADT7320 in this mode.
For microcontroller interfaces, it is recommended that SCLK
idle high between data transfers.
SERIAL INTERFACE RESET
The serial interface can be reset by writing a series of 1s on the
DIN input. If a Logic 1 is written to the ADT7320 DIN line for
at least 32 serial clock cycles, the serial interface is reset. This
ensures that the interface can be reset to a known state if the
interface is lost due to a software error or a glitch in the system.
A reset returns the interface to the state in which it expects a
write to a communications register. This operation resets the
contents of all registers to their power-on values. Following a
reset, allow a period of 500 μs before addressing the serial
interface.
Rev. 0 | Page 19 of 24
ADT7320
Data Sheet
INT AND CT OUTPUTS
Comparator Mode
The INT and CT pins are open-drain outputs, and both pins
require a 10 kΩ pull-up resistor to VDD. The ADT7320 must be
fully powered up to VDD before reading INT and CT data.
In comparator mode, the INT pin returns to its inactive status
when the temperature drops below the THIGH − THYST limit or
rises above the TLOW + THYST limit.
UNDERTEMPERATURE AND OVERTEMPERATURE
DETECTION
Placing the ADT7320 into shutdown mode does not reset the
INT state in comparator mode.
The INT and CT pins have two undertemperature/overtemperature
modes: comparator mode and interrupt mode. The interrupt
mode is the default power-up overtemperature mode. The INT
output pin becomes active when the temperature is greater than
the temperature stored in the THIGH setpoint register or less than
the temperature stored in the TLOW setpoint register. How this
pin reacts after an undertemperature or overtemperature event
depends on the overtemperature mode selected.
Interrupt Mode
In interrupt mode, the INT pin returns to its inactive status
when any ADT7320 register is read. When the INT pin is reset,
it becomes active again only when the temperature is greater
than the temperature stored in the THIGH setpoint register or less
than the temperature stored in the TLOW setpoint register.
Placing the ADT7320 into shutdown mode resets the INT pin in
interrupt mode.
Figure 19 illustrates the comparator and interrupt modes for
events exceeding the THIGH limit with both pin polarity settings.
Figure 20 illustrates the comparator and interrupt modes for
events exceeding the TLOW limit with both pin polarity settings.
TEMPERATURE
82°C
81°C
THIGH
80°C
79°C
78°C
77°C
76°C
THIGH – THYST
75°C
74°C
73°C
INT PIN
(COMPARATOR MODE)
POLARITY = ACTIVE LOW
INT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE LOW
INT PIN
(COMPARATOR MODE)
POLARITY = ACTIVE HIGH
TIME
READ
READ
READ
Figure 19. INT Output Temperature Response for THIGH Overtemperature Events
Rev. 0 | Page 20 of 24
09012-020
INT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE HIGH
Data Sheet
ADT7320
TEMPERATURE
–13°C
–14°C
TLOW + THYST
–15°C
–16°C
–17°C
–18°C
–19°C
TLOW
–20°C
–21°C
–22°C
INT PIN
(COMPARATOR MODE)
POLARITY = ACTIVE LOW
INT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE LOW
INT PIN
(COMPARATOR MODE)
POLARITY = ACTIVE HIGH
TIME
READ
READ
READ
Figure 20. INT Output Temperature Response for TLOW Undertemperature Events
Rev. 0 | Page 21 of 24
09012-021
INT PIN
(INTERRUPT MODE)
POLARITY = ACTIVE HIGH
ADT7320
Data Sheet
APPLICATIONS INFORMATION
THERMAL RESPONSE TIME
POWERING FROM A SWITCHING REGULATOR
Thermal response is a function of the thermal mass of the
temperature sensor, but it is also heavily influenced by the
mass of the object that the IC is mounted to. For example, a large
PCB containing large amounts of copper tracing can act as a
large heat sink and slow the thermal response. For a faster thermal
response, it is recommended that the sensor be mounted on a
PCB that is as small as possible.
Precision analog devices such as the ADT7320 require a wellfiltered power source. If the ADT7320 is powered from a switching
regulator, noise may be generated above 50 kHz that may affect
the temperature accuracy specifications. To prevent this, an RC
filter should be used between the power supply and ADT7320
VDD. The value of the components used should be carefully
considered to ensure that the peak value of the supply noise is
less than 1 mV. The RC filter should be mounted as far away as
possible from the ADT7320 to ensure that the thermal mass is
kept as low as possible.
Figure 10 shows the typical response time of less than 2 seconds to
reach 63.2% of the temperature span of the DUT. The temperature
values are the digital bytes read back through the digital interface.
The response time includes all delays incurred on chip during
signal processing.
SUPPLY DECOUPLING
The ADT7320 must have a decoupling capacitor connected
between VDD and GND; otherwise, incorrect temperature
readings will be obtained. A 0.1 μF decoupling capacitor, such
as a high frequency ceramic type, must be used and mounted as
close as possible to the VDD pin of the ADT7320.
If possible, the ADT7320 should be powered directly from the
system power supply. This arrangement, shown in Figure 21,
isolates the analog section from the logic switching transients.
Even if a separate power supply trace is not available, generous
supply bypassing reduces supply line induced errors. Local
supply bypassing consisting of a 0.1 μF ceramic capacitor is
critical for the temperature accuracy specifications to be
achieved.
TTL/CMOS
LOGIC
CIRCUITS
0.1µF
TEMPERATURE MEASUREMENT
The ADT7320 accurately measures and converts the temperature
at the surface of its own semiconductor chip. Thermal paths run
through the leads, the exposed pad, as well as the plastic package.
When the ADT7320 is used to measure the temperature of a
nearby heat source, the thermal impedance between the heat
source and the ADT7320 must be considered because this
impedance affects the accuracy and thermal response of the
measurement.
For air or surface temperature measurements, take care to isolate
the package, leads, and exposed pad from ambient air temperature.
Use of a thermally conductive adhesive can help to achieve a
more accurate surface temperature measurement.
QUICK GUIDE TO MEASURING TEMPERATURE
The following is a quick guide for measuring temperature in
continuous conversion mode (default power-up mode). Execute
each step sequentially.
1.
ADT7320
POWER
SUPPLY
09012-022
2.
3.
Figure 21. Use of Separate Traces to Reduce Power Supply Noise
4.
Rev. 0 | Page 22 of 24
After power-up, reset the serial interface (load 32
consecutive 1s on DIN). This ensures all internal circuitry
is properly initialized.
Verify the setup by reading the device ID
(Register Address 0x03). It should read 0xC3.
After consistent consecutive readings are obtained from
Step 2, read the configuration register (Register Address 0x01),
TCRIT (Register Address 0x04), THIGH (Register Address 0x06),
and TLOW (Register Address 0x07). Compare these values
with the specified defaults in Table 6. If all the readings
match, the interface is operational.
Write to the configuration register to set the ADT7320 to
the desired configuration. Read the temperature value register.
It should produce a valid temperature measurement.
Data Sheet
ADT7320
OUTLINE DIMENSIONS
PIN 1
INDICATOR
4.10
4.00 SQ
3.90
0.35
0.30
0.25
0.65
BSC
16
13
PIN 1
INDICATOR
12
1
EXPOSED
PAD
4
2.70
2.60 SQ
2.50
9
0.80
0.75
0.70
0.45
0.40
0.35
8
0.05 MAX
0.02 NOM
COPLANARITY
0.08
0.20 REF
SEATING
PLANE
5
BOTTOM VIEW
0.20 MIN
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
COMPLIANT TO JEDEC STANDARDS MO-220-WGGC.
08-16-2010-C
TOP VIEW
Figure 22. 16-Lead Lead Frame Chip Scale Package [LFCSP_WQ]
4 mm × 4 mm Body, Very Very Thin Quad
(CP-16-17)
Dimensions shown in millimeters
ORDERING GUIDE
Model 1
ADT7320UCPZ-R2
ADT7320UCPZ-RL7
EVAL-ADT7X20EBZ
1
2
Temperature Range 2
−40°C to +150°C
−40°C to +150°C
Package Description
16-lead LFCSP_WQ
16-Lead LFCSP_WQ
Evaluation Board
Z = RoHS Compliant Part.
Operating at extended temperatures over prolonged periods may shorten the lifetime performance of the part.
Rev. 0 | Page 23 of 24
Package Option
CP-16-17
CP-16-17
ADT7320
Data Sheet
NOTES
©2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D09012-0-12/12(0)
Rev. 0 | Page 24 of 24
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement