±0.5°C Accurate, 10-Bit Digital Temperature Sensors in SOT-23 AD7414/AD7415

±0.5°C Accurate, 10-Bit Digital Temperature Sensors in SOT-23 AD7414/AD7415
±0.5°C Accurate, 10-Bit Digital
Temperature Sensors in SOT-23
AD7414/AD7415
FUNCTIONAL BLOCK DIAGRAM
FEATURES
APPLICATIONS
Hard disk drives
Personal computers
Electronic test equipment
Office equipment
Domestic appliances
Process control
Cellular phones
GND
10-BIT
ANALOG-DIGITAL
CONVERTER
BAND GAP
TEMPERATURE
SENSOR
VDD
CONFIGURATION
REGISTER
TEMPERATURE
VALUE
REGISTER
THIGH SETPOINT
REGISTER
SETPOINT
COMPARATOR
TLOW SETPOINT
REGISTER
SMBus/I2C
INTERFACE
AS
ALERT
SCL
SDA
AD7414
AD7415
GND
BAND GAP
TEMPERATURE
SENSOR
10-BIT
ANALOG-DIGITAL
CONVERTER
CONFIGURATION
REGISTER
TEMPERATURE
VALUE
REGISTER
VDD
AS
SMBus/I2C
INTERFACE
SCL
SDA
02463-001
10-bit temperature-to-digital converter
Temperature range: −40°C to +125°C
Typical accuracy of ±0.5°C at +40°C
SMBus/I2C®-compatible serial interface
3 μA power-down current
Temperature conversion time: 29 μs typ
Space-saving 6-lead (AD7414) and 5-lead (AD7415)
SOT-23 packages
Pin selectable addressing via AS
Overtemperature indicator (AD7414 Only)
SMBus alert function (AD7414 only)
4 versions allow 8 I2C addresses (AD7414)
2 versions allow 6 I2C addresses (AD7415)
Figure 1.
GENERAL DESCRIPTION
The AD7414/AD7415 are complete temperature monitoring
systems in 6-lead and 5-lead SOT-23 packages. They contain a
band gap temperature sensor and a 10-bit ADC to monitor and
digitize the temperature reading to a resolution of 0.25°C.
limit is exceeded. A configuration register allows programming of
the state of the ALERT output (active high or active low). This
output can be used as an interrupt or as an SMBus alert.
The AD7414/AD7415 provide a 2-wire serial interface that is
compatible with SMBus and I2C interfaces. The parts come in four
versions: the AD7414/AD7415-0, AD7414/AD7415-1, AD7414-2,
and AD7414-3. The AD7414/AD7415-0 and AD7414/AD7415-1
versions provide a choice of three different SMBus addresses for
each version. All four AD7414 versions give the possibility of eight
different I2C addresses while the two AD7415 versions allow up to
six I2C addresses to be used.
1. On-chip temperature sensor. The sensor allows an accurate
measurement of the ambient temperature to be made. It is
capable of ±0.5°C temperature accuracy.
The AD7414/AD7415’s 2.7 V supply voltage, low supply current,
serial interface, and small package size make them ideal for a
variety of applications, including personal computers, office
equipment, cellular phones, and domestic appliances.
In the AD7414, on-chip registers can be programmed with high
and low temperature limits, and an open-drain overtemperature
indicator output (ALERT) becomes active when a programmed
PRODUCT HIGHLIGHTS
2. SMBus/I2C-compatible serial interface. The interface offers pin
selectable choice of three addresses per version of the
AD7414/AD7415, eight address options in total for the AD7414,
and six in total for the AD7415.
3. Supply voltage of 2.7 V to 5.5 V.
4. Space-saving 5-lead and 6-lead SOT-23 packages.
5. 10-bit temperature reading to 0.25°C resolution.
6. Overtemperature indicator. This indicator can be software
disabled. It is used as an interrupt of SMBus alert.
7. One-shot and automatic temperature conversion rates.
Rev. F
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
www.analog.com
Fax: 781.461.3113 ©2001–2010 Analog Devices, Inc. All rights reserved.
AD7414/AD7415
TABLE OF CONTENTS
Specifications ..................................................................................... 3 Serial Interface ................................................................................. 12 Absolute Maximum Ratings ............................................................ 5 Serial Bus Address....................................................................... 12 ESD Caution .................................................................................. 5 Write Mode .................................................................................. 12 Pin Configurations and Function Descriptions ............................ 6 Read Mode ................................................................................... 12 Theory of Operation ......................................................................... 7 SMBUS ALERT............................................................................. 13 Circuit Information ...................................................................... 7 Power-On Defaults ..................................................................... 13 Functional Description................................................................. 7 Operating Modes ........................................................................ 13 Measurement Technique .............................................................. 7 Power vs. Throughput ................................................................ 14 Temperature Data Format ............................................................ 8 Mounting the AD7414/AD7415 ............................................... 14 Internal Register Structure ............................................................... 9 Supply Decoupling ...................................................................... 14 Address Pointer Register .............................................................. 9 Temperature Accuracy vs. Supply ............................................. 15 Configuration Register (Address 0X01) ..................................... 9 Typical Temperature Error Graph ............................................ 15 Temperature Value Register (Address 0X00) ...........................10 Outline Dimensions ........................................................................ 16 AD7414 THIGH Register (Address 0X02) ...................................10 Ordering Guide ........................................................................... 18 AD7414 TLOW Register (Address 0X03) ....................................10 REVISION HISTORY
11/10—Rev. E to Rev. F
Added Data Hold Time, t7 Parameter, Table 1 .............................. 4
Changes to Figure 2........................................................................... 4
Updated to Outline Dimensions ...................................................16
Changes to Ordering Guide ...........................................................18
Updated Circuit Information .......................................................... 5
Updated Temperature Data Format................................................ 6
Updated Temperature Value Register ............................................. 8
Updated Figure 14 ........................................................................... 11
Updated Outline Dimensions........................................................ 12
4/05—Rev. D to Rev. E
Updated Format.................................................................. Universal
Changes to Absolute Maximum Ratings ........................................ 6
Changes to Figure 6........................................................................... 7
Changes to Ordering Guide ...........................................................17
11/02—Rev. A to Rev. B.
Changes to Absolute Maximum Ratings........................................ 3
9/04—Rev. C to Rev. D.
Changes to Absolute Maximum Ratings ........................................ 3
Updated Ordering Guide ................................................................. 4
8/03—Rev. B to Rev. C.
Change to Temperature Range ......................................... Universal
Updated Features ............................................................................... 1
Updated Specifications ..................................................................... 2
Updated Absolute Maximum Ratings ............................................ 3
Updated Ordering Guide ................................................................. 4
10/02—Rev. 0 to Rev. A.
Changes to Specifications ................................................................ 2
Changes to Pin Function Descriptions .......................................... 3
Changes to Absolute Maximum Ratings........................................ 3
Ordering Guide Updated ................................................................. 4
Change to Figure 2 ............................................................................ 5
Added to Typical Temperature
Error Graph section ........................................................................ 11
Added Figure 15 .............................................................................. 11
Outline Dimensions updated ........................................................ 12
7/01—Revision 0: Initial Version
Rev. F | Page 2 of 20
AD7414/AD7415
SPECIFICATIONS
TA = TMIN to TMAX, VDD = 2.7 V to 5.5 V, unless otherwise noted. Temperature range as follows: A version = −40°C to +125°C.
Table 1.
Parameter
TEMPERATURE SENSOR AND ADC
Accuracy 1
Resolution
Update Rate, tR
Temperature Conversion Time
POWER SUPPLIES
Supply Current 3
Peak Supply Current 4
Supply Current – Nonconverting
Inactive Serial Bus 5
Normal Mode @ 3 V
Normal Mode @ 5 V
Active Serial Bus 6
Normal Mode @ 3 V
Normal Mode @ 5 V
Shutdown Mode
DIGITAL INPUT
Input High Voltage, VIH
Input Low Voltage, VIL
Input Current, IIN 7
Input Capacitance, CIN
DIGITAL OUTPUT (OPEN-DRAIN)
Output High Voltage, VOH
Output Low Voltage, VOL
Output High Current, IOH
Output Capacitance, COUT
ALERT Output Saturation Voltage
A Version
Unit
Test Conditions/Comments
±0.5
−0.87 to +0.82 2
±1.5
±2.0
±3.0
±2.0
±1.872
±2.0
±3.0
±3.0
10
800
25
°C typ
°C max
°C max
°C max
°C max
°C typ
°C max
°C typ
°C max
°C typ
Bits
ms typ
μs typ
VDD = 3 V @ +40°C
VDD = 3 V @ +40°C
VDD = 3 V @ −40°C to +70°C
VDD = 3 V @ −40°C to +85°C
VDD = 3 V @ −40°C to +125°C
VDD = 3 V @ −40°C to +125°C
VDD = 5.5 V @ +40°C
VDD = 5.5 V @ −40°C to +85°C
VDD = 5.5 V @ −40°C to +85°C
VDD = 5.5 V @ −40°C to +125°C
1.2
900
mA typ
μA max
Current during conversion
Peak current between conversions
169
188
μA typ
μA typ
Supply current with serial bus inactive. Part not
converting and D7 of configuration register = 0.
180
214
3
μA typ
μA typ
μA max
Supply current with serial bus active. Part not
converting and D7 of configuration register = 0.
D7 of configuration register = 1. Typical values
are 0.04 μA at 3 V and 0.5 μA at 5 V.
2.4
0.8
±1
10
V min
V max
μA max
pF max
VIN = 0 V to VDD
All digital inputs
2.4
0.4
1
10
0.8
V min
V max
μA max
pF max
V max
IOL = 1.6 mA
VOH = 5 V
Typ = 3 pF
IOUT = 4 mA
Rev. F | Page 3 of 20
AD7414/AD7415
Parameter
AC ELECTRICAL CHARACTERISTICS 8, 9
Serial Clock Period, t1
Data In Setup Time to SCL High, t2
Data Out Stable after SCL Low, t3
SDA Low Setup Time to SCL Low
(Start Condition), t4
SDA High Hold Time after SCL High
(Stop Condition), t5
SDA and SCL Fall Time, t6
Data Hold Time, t7
Power-Up Time
A Version
Unit
Test Conditions/Comments
2.5
50
0
50
μs min
ns min
ns min
ns min
See Figure 2
See Figure 2
See Figure 2
See Figure 2
50
ns min
See Figure 2
90
35
4
ns max
ns min
μs typ
See Figure 2
See Figure 2
1
Accuracy specifications apply only to voltages listed under Test Conditions. See Temperature Accuracy vs. Supply section for typical accuracy performance over the
full VDD supply range.
2
100% production tested at 40°C to these limits.
3
These current values can be used to determine average power consumption at different one-shot conversion rates. Average power consumption at the automatic
conversion rate of 1.25 kHz is 940 μW.
4
This peak supply current is required for 29 μs (the conversion time plus power-up time) out of every 800 μs (the conversion rate).
5
These current values are derived by not issuing a stop condition at the end of a write or read, thus preventing the part from going into a conversion.
6
The current is derived assuming a 400 kHz serial clock being active continuously.
7
On power-up, the initial input current, IIN, on the AS pin is typically 50 μA.
8
The SDA and SCL timing is measured with the input filters turned on so as to meet the fast mode I2C specification. Switching off the input filters improves the transfer
rate but has a negative effect on the EMC behavior of the part.
9
Guaranteed by design. Not tested in production.
t1
SCL
t4
t2
t7
t5
SDA
DATA IN
t3
t6
Figure 2. Diagram for Serial Bus Timing
Rev. F | Page 4 of 20
02463-002
SDA
DATA OUT
AD7414/AD7415
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
VDD to GND
SDA Input Voltage to GND
SDA Output Voltage to GND
SCL Input Voltage to GND
ALERT Output Voltage to GND
Operating Temperature Range
Storage Temperature Range
Junction Temperature
5-Lead SOT-23 (RJ-5)
Power Dissipation 1, 2
Thermal Impedance 3
θJA, Junction-to-Ambient (still air)
6-Lead SOT-23 (RJ-6)
Power Dissipation1, 2
Thermal Impedance3
θJA, Junction-to-Ambient (still air)
8-Lead MSOP (RM-8)
Power Dissipation1, 2
Thermal Impedance3
θJA, Junction-to-Ambient (still air)
θJC, Junction-to-Case
IR Reflow Soldering
Peak Temperature
Time at Peak Temperature
Ramp-up Rate
Ramp-down Rate
Ramp from 25°C to Peak Temperature
IR Reflow Soldering in Pb-Free Package
Peak Temperature
Time at Peak Temperature
Ramp Rate
Ramp-Down Rate
Ramp from 25°C to Peak Temperature
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.
Rating
−0.3 V to +7 V
−0.3 V to +7 V
−0.3 V to +7 V
−0.3 V to +7 V
−0.3 V to +7 V
−40°C to +125°C
−65°C to +150°C
150°C
ESD CAUTION
WMAX = (TJMAX − TA)/θJA
240°C/W
WMAX = (TJMAX − TA)/θJA
190.4°C/W
WMAX = (TJMAX − TA)/θJA
205.9°C/W
43.74°C/W
220°C (0°C/5°C)
10 sec to 20 sec
3°C/s max
−6°C/s max
6 minutes max
260°C (0°C)
20 sec to 40 sec
3°C/s max
−6°C/s max
8 minutes max
1
Values relate to package being used on a standard 2-layer PCB.
TA = ambient temperature.
3
Junction-to-case resistance is applicable to components featuring a
preferential flow direction, such as components mounted on a heat sink.
Junction-to-ambient resistance is more useful for air-cooled, PCB-mounted
components.
2
Rev. F | Page 5 of 20
AD7414/AD7415
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
8 NC
NC 1
AD7414
AD7415
5 ALERT
4 SCL
Figure 3. AD7414 Pin Configuration (SOT-23)
SDA 2
Top View
(Not to Scale)
7 AS
ALERT 3
GND 2
6 GND
SCL 4
5 VDD
NC = NO CONNECT
VDD 3
02463-004
VDD 3
Top View
(Not to Scale)
02463-003
GND 2
5 SDA
AS 1
AD7414
Top View
(Not to Scale)
4 SCL
Figure 5. AD7415 Pin Configuration (SOT-23)
Figure 4. AD7414 Pin Configuration (MSOP)
Table 3. Pin Function Descriptions
Table 4. I2C Address Selection
Mnemonic
AS
Part Number
AD7414-0
AD7414-0
AD7414-0
AD7414-1
AD7414-1
AD7414-1
AD7414-2
AD7414-3
AD7415-0
AD7415-0
AD7415-0
AD7415-1
AD7415-1
AD7415-1
GND
VDD
SDA
ALERT
SCL
Description
Logic Input. Address select input that selects one
of three I2C addresses for the AD7414/AD7415 (see
Table 4). Recommend a pull-up or pull-down
resistor of 1 kΩ.
Analog and Digital Ground.
Positive Supply Voltage, 2.7 V to 5.5 V.
Digital I/O. Serial bus bidirectional data. Opendrain output.
AD7414 Digital Output. Overtemperature
indicator becomes active when temperature
exceeds THIGH. Open-drain output.
Digital Input. Serial bus clock.
Rev. F | Page 6 of 20
02463-005
6 SDA
AS 1
AS Pin
Float
GND
VDD
Float
GND
VDD
N/A
N/A
Float
GND
VDD
Float
GND
VDD
I2C Address
1001 000
1001 001
1001 010
1001 100
1001 101
1001 110
1001 011
1001 111
1001 000
1001 001
1001 010
1001 100
1001 101
1001 110
AD7414/AD7415
THEORY OF OPERATION
Configuration functions consist of
The AD7414/AD7415 are standalone digital temperature
sensors. The on-chip temperature sensor allows an accurate
measurement of the ambient device temperature to be made.
The 10-bit analog-to-digital converter converts the temperature
measured into a twos complement format for storage in the
temperature register. The ADC is made up of a conventional
successive-approximation converter based around a capacitor
digital-to-analog (DAC). The serial interface is I2C-and SMBuscompatible. The AD7414/AD7415 require a 2.7 V to 5.5 V
power supply. The temperature sensor has a working
measurement range of −40°C to +125°C.
FUNCTIONAL DESCRIPTION
Temperature measurement is initiated by two methods. The
first uses an internal clock countdown of 800 ms, and a
conversion is performed. The internal oscillator is the only
circuit that is powered up between conversions, and once it
times out, every 800 ms, a wake-up signal is sent to power up
the rest of the circuitry. A monostable is activated at the
beginning of the wake-up signal to ensure that sufficient time is
given to the power-up process. The monostable typically takes
4 μs to time out. It then takes typically 25 μs for each conversion
to be completed. The new temperature value is loaded into the
temperature value register and ready for reading by the I2C
interface.
A temperature measurement is also initiated every time the
one-shot method is used. This method requires the user to
write to the one-shot bit in the configuration register when a
temperature measurement is needed. Setting the one-shot bit to
1 starts a temperature conversion directly after the write
operation. The track-and-hold goes into hold approximately
4 μs (monostable time out) after the STOP condition, and a
conversion is then initiated. Typically 25 μs later, the conversion
is complete and the temperature value register is loaded with a
new temperature value.
The measurement modes are compared with a high temperature limit, stored in an 8-bit read/write register. This is applicable only to the AD7414, because the AD7415 does not have an
ALERT pin and subsequently does not have an overtemperature
monitoring function. If the measurement is greater than the
high limit, the ALERT pin is activated (if it has already been
enabled in the configuration register). There are two ways to
deactivate the ALERT pin again: when the alert reset bit in the
configuration register is set to 1 by a write operation, and when
the temperature measured is less than the value in the TLOW
register. This ALERT pin is compatible with the SMBus
SMBALERT option.
• Switching between normal operation and full powerdown
• Enabling or disabling the SCL and SDA filters
• Enabling or disabling the ALERT function
• Setting the ALERT pin polarity
SUPPLY
2.7V TO
5.5V 10μF
VDD
0.1μF
10kΩ
1kΩ
VDD
10kΩ
VDD
10kΩ
VDD
AS
SDA
SCL
GND
μC/μP
ALERT
AD7414
02463-006
CIRCUIT INFORMATION
Figure 6. Typical Connection Diagram
MEASUREMENT TECHNIQUE
A common method of measuring temperature is to exploit the
negative temperature coefficient of a diode, or the base-emitter
voltage of a transistor, operated at constant current.
Unfortunately, this technique requires calibration to null the
effect of the absolute value of VBE, which varies from device to
device. The technique used in the AD7414/AD7415 is to
measure the change in VBE when the device is operated at two
different currents. This is given by
Δ VBE = KT q × ln (N )
where:
K is Boltzmann’s constant.
q is the charge on the electron (1.6 × 10–19 Coulombs).
T is the absolute temperature in Kelvins.
N is the ratio of the two currents.
Rev. F | Page 7 of 20
AD7414/AD7415
VDD
I
Table 5. A Grade Temperature Data Format
I×N
VOUT +
TO ADC
VOUT –
SENSING
TRANSISTOR
02463-007
SENSING
TRANSISTOR
Figure 7. Temperature Measurement Technique
Figure 7 shows the method the AD7414/AD7415 use to
measure the ambient device temperature. To measure ΔVBE,
the sensor (substrate transistor) is switched between operating
currents of I and N × I. The resulting waveform is passed
through a chopper stabilized amplifier that performs the
functions of amplification and rectification of the waveform to
produce a dc voltage proportional to ΔVBE. This voltage is
measured by the ADC to give a temperature output in 10-bit,
twos complement format.
TEMPERATURE DATA FORMAT
The temperature resolution of the ADC is 0.25°C, which
corresponds to 1 LSB of the ADC. The ADC can theoretically
measure a temperature span of 255°C; the lowest practical value
is limited to −40°C due to the device maximum ratings. The
A grade can measure a temperature range of −40°C to +125°C.
(Temperature data format is shown in Table 5.)
Temperature
−55°C
−50°C
−25°C
−0.25°C
0°C
+0.25°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
Digital Output DB9…DB0
11 0010 0100
11 0011 1000
11 1001 1100
11 1111 1111
00 0000 0000
00 0000 0001
00 0010 1000
00 0110 0100
00 1100 1000
01 0010 1100
01 1001 0000
01 1111 0100
The grade temperature conversion formula follows:
Positive Temperature =
ADC Code (d )
Negative Temperature =
4
ADC Code (d ) − 512
4
Note that DB9 is removed from the ADC code in the negative
temperature formula.
Rev. F | Page 8 of 20
AD7414/AD7415
INTERNAL REGISTER STRUCTURE
Table 6. Address Pointer Register
The AD7414 has five internal registers, as shown in Figure 8.
Four are data registers, and one is an address pointer register.
P7
0
P6
0
P5
0
P4
0
P3
0
P2
0
P1
P0
Register Select
Table 7. AD7414 Register Address
TEMPERATURE
VALUE
REGISTER
P1
0
0
1
1
CONFIGURATION
REGISTER
D
A
T
A
ADDRESS
POINTER
REGISTER
THIGH
REGISTER
P0
0
1
0
1
Register
Temperature value register (read-only)
Configuration register (read/write)
THIGH register (read/write)
TLOW register (read/write)
Table 8. AD7415 Register Address
P1
0
0
SDA
SERIAL BUS INTERFACE
SCL
02463-008
TLOW
REGISTER
Figure 8. AD7414 Register Structure
The AD7415 has three internal registers, as shown in Figure 9.
Two are data registers, and one is an address pointer register.
P0
0
1
Registers
Temperature value register (read-only)
Configuration register (read/write)
Table 9. AD7414 Configuration Register
D7
PD
D6
FLTR
01
11
1
D5
ALERT
EN
01
D4
ALERT
POLARITY
01
D3
ALERT
RESET
01
D2
ONE
SHOT
01
D1 D0
TEST
MODE
0s1
Default settings at power-up.
CONFIGURATION REGISTER (ADDRESS 0X01)
The configuration register is an 8-bit read/write register that is
used to set the operating modes of the AD7414/AD7415. In the
AD7414, six of the MSBs are used (D7 to D2) to set the
operating modes (see Table 10). D0 and D1 are used for factory
settings and must have zeros written to them during normal
operation.
TEMPERATURE
VALUE
REGISTER
ADDRESS
POINTER
REGISTER
CONFIGURATION
REGISTER
D
A
T
A
SCL
02463-009
Table 10. AD7414 Configuration Register Settings
SDA
Figure 9. AD7415 Register Structure
Each data register has an address pointed to by the address
pointer register when communicating with it. The temperature
value register is the only data register that is read-only.
D7
D6
D5
D4
D3
D2
ADDRESS POINTER REGISTER
The address pointer register is an 8-bit register that stores an
address that points to one of the four data registers of the
AD7414 and one of the two data registers of the AD7415. The
first byte of every serial write operation to the AD7414/AD7415
is the address of one of the data registers, which is stored in the
address pointer register and selects the data register to which
subsequent data bytes are written. Only the 2 LSBs of this
register are used to select a data register.
Full power-down if = 1.
Bypass SDA and SCL filtering if = 0.
Disable ALERT if = 1.
ALERT is active low if D4 = 0, ALERT is active high if D4 = 1.
Reset the ALERT pin if set to 1. The next temperature
conversion has the ability to activate the ALERT function.
The bit status is not stored; thus this bit is 0 if read.
Initiate a one shot temperature conversion if set to a 1.
The bit status is not stored; thus this bit is 0 if read.
Table 11. AD7415 Configuration Register
D7
PD
01
1
D6
FLTR
11
D5 D4 D3
TEST MODE
0s1
Default settings at power-up.
Rev. F | Page 9 of 20
D2
ONE SHOT
0s1
D1
D0
TEST MODE
0s1
AD7414/AD7415
In the AD7415, only three of the bits are used (D7, D6, and D2)
to set the operating modes (see Table 12). D0, D1, and D3 to D5
are used for factory settings and must have zeros written to
them during normal operation.
Table 12. AD7415 Configuration Register Settings
D7
D6
D2
Table 13. Temperature Value Register (First Read)
D15
MSB
D14
B8
D13
B7
D12
B6
D11
B5
D10
B4
D9
B3
D8
B2
Table 14. AD7414 Temperature Value Register (Second Read)
Full power-down if = 1.
Bypass SDA and SCL filtering if = 0.
Initiate a one-shot temperature conversion if set to 1.
The bit status is not stored; thus this bit is 0 if read.
D7
B1
If the AD7414/AD7415 are in power-down mode (D7 = 1), a
temperature conversion can still be initiated by the one-shot
operation. This involves a write operation to the configuration
register and setting the one-shot bit to 1 (D2 = 1), which causes
the AD7414/AD7415 to power up, perform a single conversion,
and power down again. This is a very power efficient mode.
TEMPERATURE VALUE REGISTER (ADDRESS 0X00)
The temperature value register is a 10-bit, read-only register
that stores the temperature reading from the ADC in twos
complement format. Two reads are necessary to read data from
this register. Table 13 shows the contents of the first byte to be
read, while Table 14 and Table 15 show the contents of the
second byte to be read from the AD7414 and AD7415,
respectively. In Table 14, D3 to D5 of the second byte are used
as flag bits and are obtained from other internal registers. They
function as follows:
ALERT_Flag: The state of this bit is the same as that of the
ALERT pin.
D6
LSB
D5
ALERT_Flag
D4
THIGH_Flag
D3
TLOW_Flag
D2
0
D1
0
D0
0
Table 15. AD7415 Temperature Value Register (Second Read)
D7
B1
D6
LSB
D5
N/A
D4
N/A
D3
N/A
D2
N/A
D1
N/A
D0
N/A
AD7414 THIGH REGISTER (ADDRESS 0X02)
The THIGH register (see Table 16) is an 8-bit, read/write register
that stores the upper limit that activates the ALERT output.
Therefore, if the value in the temperature value register is
greater than the value in the THIGH register, the ALERT pin is
activated (that is, if ALERT is enabled in the configuration
register). Because it is an 8-bit register, the temperature
resolution is 1°C.
Table 16. THIGH Register
D7
MSB
D6
B6
D5
B5
D4
B4
D3
B3
D2
B2
D1
B1
D0
B0
AD7414 TLOW REGISTER (ADDRESS 0X03)
THIGH_Flag:
This flag is set to 1 when the temperature
measured goes above the THIGH limit. It is reset
when the second temperature byte (Table 14) is
read. If the temperature is still greater than the
THIGH limit after the read operation, the flag is
again.
The TLOW register (see Table 17) is an 8-bit read/write register
that stores the lower limit that deactivates the ALERT output.
Therefore, if the value in the temperature value register is less
than the value in the TLOW register, the ALERT pin is
deactivated (that is, if ALERT is enabled in the configuration
register).
TLOW_Flag:
This flag is set to 1 when the temperature
measured goes below the TLOW limit. It is reset
when the second temperature byte (Table 14) is
read. If the temperature is still less than the TLOW
limit after the read operation, the flag is set again.
Because it is an 8-bit register, the temperature resolution is 1°C.
Table 17. TLOW Register
D7
MSB
The full theoretical span of the ADC is 255°C, but in practice
the temperature measurement range is limited to the operating
range of the device, −40°C to +125°C for the A grade.
Rev. F | Page 10 of 20
D6
B6
D5
B5
D4
B4
D3
B3
D2
B2
D1
B1
D0
B0
AD7414/AD7415
9
1
9
1
SCL
0
A2
1
A0
A1
P6
P7
R/W
ACK. BY
AD7414/AD7415
START BY
MASTER
P5
P3
P4
P1
P2
P0
ACK. BY
AD7414/AD7415
FRAME 2
ADDRESS POINTER REGISTER BYTE
FRAME 1
SERIAL BUS ADDRESS BYTE
STOP BY
MASTER
Figure 10. Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation
1
9
1
9
•••
SCL
SDA
1
1
1
A2
1
R/W
A0
A1
START BY
MASTER
P7
P6
P5
P4
P3
P2
P1
•••
P0
ACK. BY
AD7414/AD7415
ACK. BY
AD7414/AD7415
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
1
9
SCL (CONTINUED) • • •
SDA (CONTINUED) • • •
D6
D7
D5
D4
D3
D2
D1
D0
02463-011
ACK. BY
STOP BY
AD7414/AD7415 MASTER
FRAME 3
DATA BYTE
Figure 11. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Register
SCL
1
0
0
1
A2
A1
A0
D7
R/W
D6
D5
D4
D3
D2
D1
ACK. BY
AD7414/AD7415
START BY
MASTER
D0
NO ACK. BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
STOP BY
MASTER
FRAME 2
SINGLE DATA BYTE FROM AD7414/AD7415
02463-012
SDA
Figure 12. Reading a Single Byte of Data from a Selected Register
9
1
9
1
•••
SCL
1
0
0
1
A2
A1
START BY
MASTER
A0
D15
R/W
D14
D13
D12
D10
D11
D9
FRAME 1
SERIAL BUS ADDRESS BYTE
•••
D8
ACK. BY
MASTER
ACK. BY
AD7414/AD7415
FRAME 2
MOST SIGNIFICANT DATA BYTE FROM AD7414/AD7415
9
1
SCL (CONTINUED) • • •
SDA (CONTINUED) • • •
D7
D6
D5
D4
D3
D2
D1
D0
NO ACK. BY STOP BY
MASTER
MASTER
FRAME 3
LEAST SIGNIFICANT DATA BYTE FROM AD7414/AD7415
Figure 13. Reading Two Bytes of Data from the Temperature Value Register
Rev. F | Page 11 of 20
02463-013
SDA
02463-010
0
1
SDA
AD7414/AD7415
SERIAL INTERFACE
Control of the AD7414/AD7415 is carried out via the I2Ccompatible serial bus. The AD7414/AD7415 are connected to
this bus as slave device, under the control of a master device,
such as the processor.
SERIAL BUS ADDRESS
Like all I2C-compatible devices, the AD7414/AD7415 have a
7-bit serial address. The four MSBs of this address for the
AD7414/AD7415 are set to 1001. The AD7414/AD7415 are
available in four versions: AD7414/AD7415-0, AD7414/
AD7415-1, AD7414-2, and AD7414-3. The first two versions
have three different I2C addresses available, which are selected
by either tying the AS pin to GND, to VDD, or letting the pin
float (see Table 4). By giving different addresses for the four
versions, up to eight AD7414s or six AD7415s can be connected
to a single serial bus, or the addresses can be set to avoid
conflicts with other devices on the bus.
The serial bus protocol operates as follows.
The master initiates data transfer by establishing a START
condition, defined as a high-to-low transition on the serial data
line SDA, while the serial clock line SCL remains high. This
indicates that an address/data stream follows. All slave peripherals connected to the serial bus respond to the START condition and shift in the next eight bits, consisting of a 7-bit address
(MSB first) plus an R/W bit, which determines the direction of
the data transfer and whether data is written to or read from the
slave device.
The peripheral whose address corresponds to the transmitted
address responds by pulling the data line low during the low
period before the ninth clock pulse, known as the acknowledge
bit. All other devices on the bus remain idle while the selected
device waits for data to be read from or written to it. If the R/W
bit is 0, the master writes to the slave device. If the R/W bit is 1,
the master reads from the slave device.
Data is sent over the serial bus in sequences of nine clock
pulses, eight bits of data followed by an acknowledge bit from
the receiver of data. Transitions on the data line must occur
during the low period of the clock signal and remain stable
during the high period, because a low-to-high transition when
the clock is high may be interpreted as a STOP signal.
When all data bytes have been read or written, stop conditions
are established. In WRITE mode, the master pulls the data line
high during the 10th clock pulse to assert a STOP condition. In
READ mode, the master device pulls the data line high during
the low period before the ninth clock pulse. This is known as
No Acknowledge. The master then takes the data line low
during the low period before the 10th clock pulse, then high
during the 10th clock pulse to assert a STOP condition.
Any number of bytes of data may be transferred over the serial
bus in one operation, but it is not possible to mix read and write
in one operation. The type of operation is determined at the
beginning and cannot then be changed without starting a new
operation.
WRITE MODE
Depending on the register being written to, there are two
different writes for the AD7414/AD7415.
Writing to the Address Pointer Register for a Subsequent
Read
In order to read data from a particular register, the address
pointer register must contain the address of that register. If it
does not, the correct address must be written to the address
pointer register by performing a single-byte write operation, as
shown in Figure 10. The write operation consists of the serial
bus address followed by the address pointer byte. No data is
written to any of the data registers. A read operation is then
performed to read the register.
Writing a Single Byte of Data to the Configuration
Register,THIGH Register, or TLOW Register
All three registers are 8-bit registers, so only one byte of data
can be written to each register. Writing a single byte of data to
one of these registers consists of the serial bus address, the data
register address written to the address pointer register, followed
by the data byte written to the selected data register. This is
illustrated in Figure 11.
READ MODE
Reading data from the AD7414/AD7415 is a 1- or 2-byte
operation. Reading back the contents of the configuration
register, the THIGH register, or the TLOW register is a single-byte
read operation, as shown in Figure 12. The register address was
previously set up by a single-byte write operation to the address
pointer register. Once the register address has been set up, any
number of reads can subsequently be performed from that
register without having to write to the address pointer register
again. To read from another register, the address pointer
register has to be written to again to set up the relevant register
address.
Reading data from the temperature value register is a 2-byte
operation, as shown in Figure 13. The same rules apply for a
2-byte read as a 1-byte read.
Rev. F | Page 12 of 20
AD7414/AD7415
SMBUS ALERT
OPERATING MODES
The AD7414 ALERT output is an SMBus interrupt line for
devices that want to trade their ability to master for an extra
pin. The AD7414 is a slave-only device and uses the SMBus
ALERT to signal to the host device that it wants to talk. The
SMBus ALERT on the AD7414 is used as an overtemperature
indicator.
Mode 1
The ALERT pin has an open-drain configuration that allows the
ALERT outputs of several AD7414s to be wire-AND’ed together
when the ALERT pin is active low. Use D4 of the configuration
register to set the active polarity of the ALERT output. The
power-up default is active low. The ALERT function can be
disabled or enabled by setting D5 of the configuration register
to 1 or 0, respectively.
The host device can process the ALERT interrupt and
simultaneously access all SMBus ALERT devices through the
alert response address. Only the device that pulled the ALERT
low acknowledges the Alert Response Address (ARA). If more
than one device pulls the ALERT pin low, the highest priority
(lowest address) device wins communication rights via standard
I2C arbitration during the slave address transfer.
The ALERT output becomes active when the value in the
temperature value register exceeds the value in the THIGH
register. It is reset when a write operation to the configuration
register sets D3 to 1 or when the temperature falls below the
value stored in the TLOW register.
The ALERT output requires an external pull-up resistor. This
can be connected to a voltage different from VDD, provided the
maximum voltage rating of the ALERT output pin is not
exceeded. The value of the pull-up resistor depends on the
application, but it should be as large as possible to avoid
excessive sink currents at the ALERT output, which can heat the
chip and affect the temperature reading.
POWER-ON DEFAULTS
The AD7414/AD7415 always power up with these defaults:
Address pointer register pointing to the temperature value
register.
This is the power-on default mode of the AD7414/AD7415. In
this mode, the AD7414/AD7415 does a temperature conversion
every 800 ms and then partially powers down until the next
conversion occurs.
If a one-shot operation (setting D2 of the configuration register
to a 1) is performed between automatic conversions, a conversion is initiated right after the write operation. After this
conversion, the part returns to performing a conversion every
800 ms.
Depending on where a serial port access occurs during a
conversion, that conversion might be aborted. If the conversion
is completed before the part recognizes a serial port access, the
temperature register is updated with the new conversion. If the
conversion is completed after the part recognizes a serial port
access, the internal logic prevents the temperature register from
being updated, because corrupt data could be read.
A temperature conversion can start anytime during a serial port
access (other than a one-shot operation), but the result of that
conversion is loaded into the temperature register only if the
serial port access is not active at the end of the conversion.
Mode 2
The only other mode in which the AD7414/AD7415 operates is
the full power-down mode. This mode is usually used when
temperature measurements are required at a very slow rate. The
power consumption of the part can be greatly reduced in this
mode by writing to the part to go to a full power-down. Full
power-down is initiated right after D7 of the configuration
register is set to 1.
When a temperature measurement is required, a write
operation can be performed to power up the part and put it into
one-shot mode (setting D2 of the configuration register to a 1).
The power-up takes approximately 4 μs. The part then performs
a conversion and is returned to full power-down. The
temperature value can be read in the full power-down mode,
because the serial interface is still powered up.
THIGH register loaded with 7Fh.
TLOW register loaded with 80h.
Configuration register loaded with 40h.
Note that the AD7415 does not have any THIGH or TLOW registers.
Rev. F | Page 13 of 20
AD7414/AD7415
POWER VS. THROUGHPUT
The two modes of operation for the AD7414/AD7415 produce
different power vs. throughput performances. Mode 2 is the
sleep mode of the part, and it achieves the optimum power
performance.
The contribution to the total power dissipated by the remaining
time is 3.9 μW.
(799.971 ms/800 ms) × (5 V × 800 nA) = 3.9 μW
Thus the total power dissipated during each cycle is:
199.3 nW + 3.9 μW = 940.16 μW
Mode 1
1.1mA
IDD
800nA
800ms
29μs
TIME
02463-015
In this mode, continuous conversions are performed at a rate of
approximately one every 800 ms. Figure 14 shows the times and
currents involved with this mode of operation for a 5 V supply.
At 5 V, the current consumption for the part when converting is
1.1 mA typically, and the quiescent current is 188 μA typically.
The conversion time of 25 μs plus power-up time of typically
4 μs contributes 199.3 nW to the overall power dissipation in
the following way:
Figure 15. Mode 2 Power Dissipation
(29 μs/800 ms) × (5 × 1.1 mA) = 199.3 nW
MOUNTING THE AD7414/AD7415
The contribution to the total power dissipated by the remaining
time is 939.96 μW.
(799.97 ms/800 ms) × (5 × 1.1 μA) = 199.3 μW
Thus the total power dissipated during each cycle is
199.3 nW + 939.96 μW = 940.16 μW
1.1mA
IDD
800ms
29μs
TIME
02463-014
188μA
Figure 14. Mode 1 Power Dissipation
Mode 2
In this mode, the part is totally powered down. All circuitry
except the serial interface is switched off. The most power
efficient way of operating in this mode is to use the one-shot
method. Write to the configuration register and set the one-shot
bit to a 1. The part powers up in approximately 4 μs and then
performs a conversion. Once the conversion is finished, the
device powers down again until the PD bit in the configuration
register is set to 0 or the one-shot bit is set to 1. Figure 15 shows
the same timing as Figure 14 in mode 1; a one-shot is initiated
every 800 ms. If we take the voltage supply to be 5 V, we can
work out the power dissipation in the following way. The
current consumption for the part when converting is 1.1 mA
typically, and the quiescent current is 800 nA typically. The
conversion time of 25 μs plus the power-up time of typically
4 μs contributes 199.3 nW to the overall power dissipation in
the following way:
The AD7414/AD7415 can be used for surface or air temperature sensing applications. If the device is cemented to a surface
with thermally conductive adhesive, the die temperature is
within about 0.1°C of the surface temperature, due to the
device’s low power consumption. Care should be taken to
insulate the back and leads of the device from the air if the
ambient air temperature is different from the surface
temperature being measured.
The ground pin provides the best thermal path to the die, so the
temperature of the die is close to that of the printed circuit
ground track. Care should be taken to ensure that this is in
good thermal contact with the surface being measured.
As with any IC, the AD7414/AD7415 and their associated
wiring and circuits must be kept free from moisture to prevent
leakage and corrosion, particularly in cold conditions where
condensation is more likely to occur. Water-resistant varnishes
and conformal coatings can be used for protection. The small
size of the AD7414/AD7415 packages allows them to be
mounted inside sealed metal probes, which provide a safe
environment for the devices.
SUPPLY DECOUPLING
The AD7414/AD7415 should at least be decoupled with a 0.1μF
ceramic capacitor between VDD and GND. This is particularly
important if the AD7414/AD7415 are mounted remote from
the power supply.
(29 μs/800 ms) × (5 V × 1.1 mA) = 199.3 nW
Rev. F | Page 14 of 20
AD7414/AD7415
TEMPERATURE ACCURACY VS. SUPPLY
TYPICAL TEMPERATURE ERROR GRAPH
The temperature accuracy specifications are guaranteed for
voltage supplies of 3 V and 5.5 V only. Figure 16 gives the
typical performance characteristics of a large sample of parts
over the full voltage range of 2.7 V to 5.5 V. Figure 17 gives the
typical performance characteristics of one part over the full
voltage range of 2.7 V to 5.5 V.
Figure 18 shows the typical temperature error plots for one
device with VDD at 3.3 V and at 5.5 V.
2
–40°C
1
0
5.5V
1
0
–1
3.3V
–2
–3
+40°C
–1
–4
–40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90 95 100 110 125
TEMPERATURE (°C)
+85°C
–2
2
02463-018
TEMPERATURE ERROR (°C)
3
3
TEMPERATURE ERROR (°C)
4
4
Figure 18. Typical Temperature Error @ 3.3 V and 5.5 V
–4
2.7
3.0
SUPPLY VOLTAGE (V)
5.5
02463-016
–3
Figure 16. Typical Temperature Error vs. Supply for Large Sample of Parts
Figure 19 shows a histogram of the temperature error at
ambient temperature (40°C) over approximately 6,000 units.
Figure 19 shows that over 70% of the AD7414/AD7415 devices
tested have a temperature error within ±0.3°C.
900
4
AMBIENT TEMPERATURE = 40°C
800
3
1
0
+40°C
–1
+85°C
600
500
400
300
–2
200
–3
100
–4
2.7
3.3
5.0
SUPPLY VOLTAGE (V)
5.5
0
–1.08
–0.81
–0.54 –0.27
0
0.27
0.54
TEMPERATURE ERROR (°C)
0.81
Figure 19. Ambient Temperature Error @ 3 V
Figure 17. Typical Temperature Error vs. Supply for One Part
Rev. F | Page 15 of 20
1.08
02463-019
NUMBER OF UNITS
–40°C
02463-017
TEMPERATURE ERROR (°C)
700
2
AD7414/AD7415
OUTLINE DIMENSIONS
3.00
2.90
2.80
1.70
1.60
1.50
6
5
4
1
2
3
3.00
2.80
2.60
PIN 1
INDICATOR
0.95 BSC
1.90
BSC
1.30
1.15
0.90
0.20 MAX
0.08 MIN
0.15 MAX
0.05 MIN
10°
4°
0°
SEATING
PLANE
0.50 MAX
0.30 MIN
0.60
BSC
0.55
0.45
0.35
121608-A
1.45 MAX
0.95 MIN
COMPLIANT TO JEDEC STANDARDS MO-178-AB
Figure 20. 6-Lead Small Outline Transistor Package [SOT-23]
(RJ-6)
Dimensions shown in millimeters
3.20
3.00
2.80
8
3.20
3.00
2.80
1
5.15
4.90
4.65
5
4
PIN 1
IDENTIFIER
0.65 BSC
0.95
0.85
0.75
15° MAX
1.10 MAX
0.40
0.25
6°
0°
0.23
0.09
COMPLIANT TO JEDEC STANDARDS MO-187-AA
Figure 21. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
Rev. F | Page 16 of 20
0.80
0.55
0.40
10-07-2009-B
0.15
0.05
COPLANARITY
0.10
AD7414/AD7415
3.00
2.90
2.80
1.70
1.60
1.50
5
1
4
2
3.00
2.80
2.60
3
0.95 BSC
1.90
BSC
1.45 MAX
0.95 MIN
0.15 MAX
0.05 MIN
0.50 MAX
0.35 MIN
0.20 MAX
0.08 MIN
SEATING
PLANE
10°
5°
0°
0.60
BSC
COMPLIANT TO JEDEC STANDARDS MO-178-AA
Figure 22. 5-Lead Small Outline Transistor Package [SOT-23]
(RJ-5)
Dimensions shown in millimeters
Rev. F | Page 17 of 20
0.55
0.45
0.35
11-01-2010-A
1.30
1.15
0.90
AD7414/AD7415
ORDERING GUIDE
Model 1
AD7414ARTZ-0REEL7
AD7414ARTZ-0REEL
AD7414ARTZ-0500RL7
AD7414ARMZ-0REEL7
AD7414ARMZ-0REEL
AD7414ARMZ-0
AD7414ARTZ-1REEL7
AD7414ARTZ-1REEL
AD7414ARTZ-1500RL7
AD7414ARTZ-2REEL7
AD7414ARTZ-2REEL
AD7414ARTZ-3REEL7
AD7414ARTZ-3REEL
AD7415ARTZ-0REEL7
AD7415ARTZ-0REEL
AD7415ARTZ-0500RL7
AD7415ARTZ-1REEL7
AD7415ARTZ-1REEL
AD7415ARTZ-1500RL7
EVAL-AD7414/15EBZ
1
Temperature Range
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
Typ Temperature
Error @ 3 V
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
±2°C
Package
Option
RJ-6
RJ-6
RJ-6
RM-8
RM-8
RM-8
RJ-6
RJ-6
RJ-6
RJ-6
RJ-6
RJ-6
RJ-6
RJ-5
RJ-5
RJ-5
RJ-5
RJ-5
RJ-5
Z = RoHS Compliant Part.
Rev. F | Page 18 of 20
Package Description
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
6-Lead SOT-23
5-Lead SOT-23
5-Lead SOT-23
5-Lead SOT-23
5-Lead SOT-23
5-Lead SOT-23
5-Lead SOT-23
Evaluation Board
Branding
#CHA
#CHA
#CHA
TOL
TOL
TOL
TOH
TOH
TOH
TOJ
TOJ
TOK
TOK
#CGA
#CGA
#CGA
#CGB
#CGB
#CGB
Ordering
Quantity
3,000
10,000
500
3,000
10,000
50
3,000
10,000
500
3,000
10,000
3,000
10,000
3,000
10,000
500
3,000
10,000
500
AD7414/AD7415
NOTES
Rev. F | Page 19 of 20
AD7414/AD7415
NOTES
I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors).
©2001–2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D02463-0-11/10(F)
Rev. F | Page 20 of 20
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

advertising