Datasheet AD7418ARM, AD7418AR, AD7417BR, AD7417AR, AD7416ARM Datasheet (Analog Devices)

...
Page 1
10-Bit Digital Temperature Sensor (AD7416) and
a
Four/Single-Channel ADCs (AD7417/AD7418)
FEATURES 10-Bit ADC with 15 s and 30 s Conversion Times Single and Four Single-Ended Analog Input Channels On-Chip Temperature Sensor: –55C to +125ⴗC On-Chip Track/Hold Over-Temperature Indicator Automatic Power Down at the End of a Conversion Wide Operating Supply Range: 2.7 V to 5.5 V
2C®
-Compatible Serial Interface
I Selectable Serial Bus Address Allows Connection of Up
to Eight AD7416/AD7417s to a Single Bus
AD7416 is a Superior Replacement for LM75
APPLICATIONS Data Acquisition with Ambient Temperature Monitoring Industrial Process Control Automotive Battery Charging Applications Personal Computers
GENERAL DESCRIPTION
The AD7417 and AD7418 are 10-bit, 4- and single-channel A/D converters with an on-chip temperature sensor that can operate from a single 2.7 V to 5.5 V power supply. The devices contain a 15 µs successive-approximation converter, a 5-channel multiplexer, a temperature sensor, a clock oscillator, a track/ hold, and a reference (2.5 V). The AD7416 is a temperature­monitoring-only device in an 8-lead package.
The temperature sensor on the parts can be accessed via multi­plexer Channel 0. When Channel 0 is selected and a conversion is initiated, the resulting ADC code at the end of the conversion gives a measurement of the ambient temperature (±1°C @ 25°C). On-chip registers can be programmed with high and low tem­perature limits, and an open drain Over-Temperature Indicator (OTI) output is provided, which becomes active when a pro­grammed limit is exceeded.
A configuration register allows programming of the sense of the OTI output (active high or active low) and its operating mode (comparator or interrupt). A programmable fault queue counter allows the number of out of limit measurements that must occur before triggering the OTI output to be set, to prevent spurious triggering of the OTI output in noisy environments.
(continued on page 7)
I2C is a registered trademark of Philips Corporation.
A0
A1
A2
V
IN1
V
IN2
V
IN3
V
IN4
NC = NO CONNECT
V
IN1
AD7416/AD7417/AD7418
FUNCTIONAL BLOCK DIAGRAMS
BANDGAP
TEMPERATURE
SENSOR
ADDRESS
POINTER
REGISTER
TEMP
SENSOR
MUX
NC NC GND
V
DD
TEMP
SENSOR
MUX
AGND
REF
REF
2.5V
SAMPLING
CAPACITOR
REF
2.5V
SAMPLING
CAPACITOR
ANALOG-DIGITAL
CONVERTER
TEMPERATURE
VALUE
REGISTER
T
OTI
REGISTER
T
HYST
REGISTER
CONFIGURATION
REGISTER
SERIAL BUS
INTERFACE
IN
V
BALANCE
REF
IN
V
BALANCE
10-BIT
SETPOINT
SETPOINT
V
DD
OVER-TEMP REG
CHARGE
DISTRIBUTION
DAC
CONTROL
CLOCK
CONVST
OVER-TEMP REG
CLOCK
CONVST
LOGIC
+
CHARGE
DISTRIBUTION
DAC
CONTROL
LOGIC
+
AD7416
SETPOINT
COMPARATOR
FAULT
QUEUE
COUNTER
A > B
B
A
DATA OUT
I2C
INTERFACE
AD7417
A > B
B
A
DATA OUT
I2C
INTERFACE
AD7418
A2A1A0
+V
OTI
GND
SDA
SCL
OTI
SCL
SDA
OTI
SCL
SDA
S
REV. D
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. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 2002
Page 2
AD7416/AD7417/AD7418
AD7417/AD7418–SPECIFICATIONS
Parameter A Version B Version
(VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted)
1
Unit Test Conditions/Comments
DC ACCURACY Any Channel
Resolution 10 10 Bits Minimum Resolution for Which No
Missing Codes are Guaranteed 10 10 Bits
Relative Accuracy
Differential Nonlinearity
Gain Error
Gain Error Match Offset Error
2
2
2
2
2
± 1 ± 1 LSB max This Spec Is Typical for VDD of
3.6 V to 5.5 V
± 1 ± 1 LSB max This Spec Is Typical for VDD of
3.6 V to 5.5 V
± 3 ± 3 LSB max External Reference ± 10 ± 10 LSB max Internal Reference ± 0.6 ± 0.6 LSB max AD7417 Only ± 4 ± 4 LSB max
Offset Error Match ± 0.7 ± 0.7 LSB max AD7417 Only
ANALOG INPUTS
Input Voltage Range V
Input Leakage Current
3
REF
V
REF
00V min ± 1 ± 1 µA max
V max
Input Capacitance 10 10 pF max
TEMPERATURE SENSOR
1
Measurement Error
Ambient Temperature 25°C ± 2 ± 1 °C max T
MIN
to T
MAX
± 3 ± 2 °C max
Temperature Resolution 1/4 1/4 °C/LSB
CONVERSION RATE
Track/Hold Acquisition Time
4
400 400 ns max Source Impedance < 10
Conversion Time
Temperature Sensor 30 30 µs max Typically 27 µs
Channels 1 to 4 15 15 µs max Typically 10 µs
REFERENCE INPUT
REFIN Input Voltage Range
5, 6
6
2.625 2.625 V max 2.5 V + 5%
2.375 2.375 V min 2.5 V – 5% Input Impedance 40 40 k min Input Capacitance 10 10 pF max
ON-CHIP REFERENCE Nominal 2.5 V
Reference Error Temperature Coefficient
6
6
± 25 ± 25 mV max 80 80 ppm/°C typ
DIGITAL INPUTS
Input High Voltage, V Input Low Voltage, V
IL
IH
+VS × 0.7 +VS × 0.7 V min +VS × 0.3 +VS × 0.3 V max
Input Leakage Current 1 1 µA max
DIGITAL OUTPUTS
Output Low Voltage, V
OL
0.4 0.4 V max IOL = 3 mA Output High Current 1 1 µA max VOH = 5 V
POWER REQUIREMENTS
V
DD
5.5 5.5 V max For Specified Performance
2.7 2.7 V min I
DD
Logic Inputs = 0 V or V Normal Operation 600 600 µA max Power Down 1 1 µA max 50 nA Typically
Auto Power-Down Mode V
= 3 V. See Operating Modes
DD
10 sps Throughput Rate 6 6 µW typ 1 ksps Throughput Rate 60 60 µW typ 10 ksps Throughput Rate 600 600 µW typ
Power Down 3 3 µW max Typically 0.15 µW
DD
–2–
REV. D
Page 3
AD7416/AD7417/AD7418
NOTES
1
B version applies to AD7417 only with temperature range of –40°C to +85°C. A version temperature range is –55°C to +125°C. For VDD = 2.7 V, TA = 85°C max and temperature sensor measurement error = ± 3°C.
2
See Terminology.
3
Refers to the input current when the part is not converting. Primarily due to reverse leakage current in the ESD protection diodes.
4
Sample tested during initial release and after any redesign or process change that may affect this parameter.
5
On-chip reference shuts down when external reference is applied.
6
The accuracy of the temperature sensor is affected by reference tolerance. The relationship between the two is explained in the section titled Temperature Sensor.
Specifications subject to change without notice.
AD7416–SPECIFICATIONS
(VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted)
Parameter Min Typ Max Unit Test Conditions/Comments
TEMPERATURE SENSOR AND ADC
Accuracy ± 2.0 °CT
± 3.0 °CT
= –25°C to +100°C (VDD = 3 V min)
A
= –55°C to +125°C (VDD = 3 V min)
A
Resolution 10 Bits Temperature Conversion Time 40 µs Update Rate, t OTI Delay 1 × t
R
R
Supply Current 1.0 mA I
400 µs
6 × t
R
350 600 µAI
ms Depends on Fault Queue Setting
2
C Active
2
C Inactive
0.2 1.5 µA Shutdown Mode
Default Temperature 80 °C
T
OTI
T
Default Temperature 75 °C
HYST
DIGITAL INPUTS
Input High Voltage, V Input Low Voltage, V
IL
Input High Current, I Input Low Current, I Input Capacitance, C
IL
IN
IH
IH
+VS × 0.7 +VS + 0.5 V –0.3 +VS × 0.3 V
0.005 1.0 µAV –0.005 –1.0 µAV 20 pF All Digital Inputs
= 5 V
IN
= 0 V
IN
DIGITAL OUTPUTS
Output Low Voltage, V
OL
Output High Current 1 µAV Output Fall Time, t OS Output Low Voltage, V
AC ELECTRICAL CHARACTERISTICS
Serial Clock Period, t Data In Setup Time to SCL High, t Data Out Stable after SCL Low, t
f
OL
2
1
2
3
2.5 µs See Figure 1 50 ns See Figure 1 0 ns See Figure 1
0.4 V IOL = 3 mA = 5 V
OH
250 ns CL = 400 pF, IO = 3 mA
0.8 V I
OUT
= 4 mA
AD7416/AD7417/AD7418
SDA Low Setup Time to SCL Low
(Start Condition), t
4
50 ns See Figure 1
SDA High Hold Time after SCL High
(Stop Condition), t
SDA and SCL Fall Time, t
NOTES
1
For VDD = 2.7 V to 3 V, TA max = 85°C and accuracy = ± 3°C.
2
Sample tested during initial release and after any redesign or process change that may affect this parameter.
Specifications subject to change without notice.
5
6
50 ns See Figure 1
300 ns See Figure 1
1
1
t
1
SCL
SDA
DATA IN
SDA
DATA OUT
t
4
t
2
Figure 1. Diagram for Serial Bus Timing
REV. D –3–
t
5
t
3
t
6
Page 4
AD7416/AD7417/AD7418
AD7417 PIN FUNCTION DESCRIPTION
Pin No. Mnemonic Description
1, 16 NC No Connection. Do not connect anything to this pin.
2 SDA Digital I/O. Serial Bus Bidirectional Data. Push-pull output. 3 SCL Digital Input. Serial Bus Clock. 4 OTI This is a logic output. The Over Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (temperature sensor) is greater than an 8-bit word in the Over Temperature Register (OTR). The signal is reset at the end of a serial read operation. Open-drain output.
5 REF
IN
6 GND Ground Reference for Track/Hold, Comparator and Capacitor DAC, and Digital Circuitry. 7–10 A
IN1
to A
11 A2 Digital Input. The highest programmable bit of the Serial Bus Address. 12 A1 Digital Input. The middle programmable bit of the Serial Bus Address. 13 A0 Digital Input. The lowest programmable bit of the Serial Bus Address. 14 V
DD
15 CONVST Logic Input Signal. Convert Start Signal. The rising edge of this signal fully powers up the part. The
Reference Input. An external 2.5 V reference can be connected to the AD7417 at this pin. To enable the on-chip reference the REF
pin should be tied to GND. If an external reference is connected to
IN
the AD7417, the internal reference will shut down.
Analog Input Channels. The AD7417 has four analog input channels. The input channels are single-
IN4
ended with respect to GND. The input channels can convert voltage signals in the range 0 V to V A channel is selected by writing to the configuration register of the AD7417. (See Control Byte section.)
Positive Supply Voltage, 2.7 V to 5.5 V.
power-up time for the part is 4 µs. If the CONVST pulse is greater than 4 µs, the falling edge of CONVST places the track/hold mode into hold mode and initiates a conversion. If the pulse is less than 4 µs, an internal timer ensures that the track/hold does not go into hold and conversion is not initiated until the power-up time has elapsed. The track/hold goes into track mode again at the end of conversion. (See Operating Mode section.)
REF
.
AD7417 PIN CONFIGURATION
SOIC/TSSOP
1
NC
2
SDA
3
SCL
4
OTI
5
REF
IN
6
GND
7
A
IN1
8
A
IN2
NC = NO CONNECT
AD7417
TOP VIEW
(Not to Scale)
16
15
14
13
12
11
10
9
NC
CONVST
V
DD
A0
A1
A2
A
IN4
A
IN3
–4–
REV. D
Page 5
AD7416/AD7417/AD7418

AD7416 PIN FUNCTION DESCRIPTION

Pin No. Mnemonic Description
1 SDA Digital I/O. Serial Bus Bidirectional Data. Push-pull output. 2 SCL Digital Input. Serial Bus Clock.
3 OTI This is a logic output. The Over-Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Over-Temperature Register
(OTR). The signal is reset at the end of a serial read operation. Open-drain output. 4 GND Ground reference for track/hold, comparator and capacitor DAC, and digital circuitry. 5 A2 Digital Input. The highest programmable bit of the Serial Bus Address. 6 A1 Digital Input. The middle programmable bit of the Serial Bus Address. 7 A0 Digital Input. The lowest programmable bit of the Serial Bus Address. 8VDDPositive Supply Voltage, 2.7 V to 5.5 V.

AD7418 PIN FUNCTION DESCRIPTION

Pin No. Mnemonic Description
1 SDA Digital I/O. Serial Bus Bidirectional Data. Push-pull output. 2 SCL Digital Input. Serial Bus Clock.
3 OTI This is a logic output. The Over-Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Over-Temperature Register
(OTR). The signal is reset at the end of a serial read operation. Open-drain output. 4 GND Ground reference for track/hold, comparator and capacitor DAC, and digital circuitry. 5A
6 REF
7V
IN
IN
DD
8 CONVST Logic Input Signal. Convert Start Signal. The rising edge of this signal fully powers up the part.
Analog Input Channel. The input channel is single-ended with respect to GND. The input channel
can convert voltage signals in the range 0 V to V
. The analog input channel is selected by writing
REF
to the configuration register of the AD7418 and choosing Channel 4. (See Control Byte section.)
Reference Input. An external 2.5 V reference can be connected to the AD7418 at this pin. To enable
the on-chip reference the REF
pin should be tied to GND. If an external reference is connected to
IN
the AD7418, the internal reference will shut down.
Positive Supply Voltage, 2.7 V to 5.5 V.
The power-up time for the part is 4 µs. If the CONVST pulse is greater than 4 µs, the falling edge
of CONVST places the track/hold mode into hold mode and initiates a conversion. If the pulse is
less than 4 µs, an internal timer ensures that the track/hold does not go into hold and conversion is
not initiated until the power-up time has elapsed. The track/hold goes into track mode again at the
end of conversion. (See Operating Mode section.)
REV. D
AD7416 PIN CONFIGURATION
SOIC/SOIC
SDA
SCL
OTI
GND
1
2
AD7416
TOP VIEW
3
(Not to Scale)
4
8
V
DD
7
A0
6
A1
5
A2
–5–
AD7418 PIN CONFIGURATION
SOIC/SOIC
SDA
SCL
OTI
GND
1
2
AD7418
TOP VIEW
3
(Not to Scale)
4
8
CONVST
7
V
6
REF
5
A
DD
IN
IN
Page 6
AD7416/AD7417/AD7418
WARNING!
ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS

(TA = 25°C unless otherwise noted)
1
VDD to AGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
V
to DGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
DD
Analog Input Voltage to AGND
to A
A
IN1
Reference Input Voltage to AGND
Digital Input Voltage to DGND . . . . . . –0.3 V to V
Digital Output Voltage to DGND . . . . . –0.3 V to V
. . . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V
IN4
2
. . . –0.3 V to V
DD
DD
DD
+ 0.3 V + 0.3 V + 0.3 V
Operating Temperature Range
A Version . . . . . . . . . . . . . . . . . . . . . . . . . –55°C to +125°C
B Version . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150°C
TSSOP, Power Dissipation . . . . . . . . . . . . . . . . . . . . 450 mW
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 120°C/W
θ
JA
Lead Temperature, Soldering . . . . . . . . . . . . . . . . . . 260°C
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
16-Lead SOIC Package, Power Dissipation . . . . . . . . 450 mW
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 100°C/W
θ
JA
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
8-Lead SOIC Package, Power Dissipation . . . . . . . . . 450 mW
θ
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 157°C/W
JA
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
µSOIC Package, Power Dissipation . . . . . . . . . . . . . . 450 mW
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 206°C/W
θ
JA
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
NOTES
1
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 listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating condi­tions for extended periods may affect device reliability.
2
If the Reference Input Voltage is likely to exceed VDD by more than 0.3 V (e.g., during power-up) and the reference is capable of supplying 30 mA or more, it is recommended to use a clamping diode between the REFIN pin and VDD pin. The diagram below shows how the diode should be connected.
REF
IN
BAT81
AD7417
V
DD

ORDERING GUIDE

Temperature Temperature Package Branding Package
Model Range Error @ 25ⴗC Description Information Options
AD7416AR –55°C to +125°C ± 2°C 8-Lead Narrow Body (SOIC) SO-8 AD7416ARM –55°C to +125°C ± 2°C 8-Lead µSOIC C6A RM-8 AD7417AR –55°C to +125°C ± 2°C 16-Lead Narrow Body (SOIC) R-16A AD7417ARU –55°C to +125°C ± 2°C 16-Lead (TSSOP) RU-16 AD7417BR –40°C to +85°C ±1°C 16-Lead Narrow Body (SOIC) R-16A AD7418AR –55°C to +125°C ± 2°C 8-Lead Narrow Body (SOIC) SO-8 AD7418ARM –55°C to +125°C ± 2°C 8-Lead µSOIC C7A RM-8
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7416/AD7417/AD7418 features proprietary ESD protection circuitry, perma­nent damage may occur on devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality .
–6–
REV. D
Page 7
AD7416/AD7417/AD7418
(continued from page 1)
An I2C-compatible serial interface allows the AD7416/AD7417/ AD7418 registers to be written to and read back. The 3 LSBs of the AD7416/AD7417s serial bus address can be selected, which allows up to eight AD7416/AD7417s to be connected to a single bus.
The AD7417 is available in a narrow body 0.15'' 16-lead small outline IC (SOIC) and in a 16-lead, thin shrink small outline package (TSSOP). The AD7416 and AD7418 are available in 8-lead SOIC and µSOIC packages.

PRODUCT HIGHLIGHTS

1. The AD7416/AD7417/AD7418 have an on-chip tempera­ture sensor that allows an accurate measurement of the am­bient temperature (±1°C @ 25°C, ± 2°C over temperature) to be made. The measurable temperature range is –55°C to +125°C. An over-temperature indicator is implemented by carrying out a digital comparison of the ADC code for Channel 0 (temperature sensor) with the contents of the on-chip over-temperature register.
2. The AD7417 offers a space saving 10-bit A/D solution with four external voltage input channels, an on-chip temperature sensor, an on-chip reference and clock oscillator.
3. The automatic power-down feature enables the AD7416/ AD7417/AD7418 to achieve superior power performance. At slower throughput rates the part can be programmed to operate in a low power shutdown mode allowing further savings in power consumption.
TERMINOLOGY Relative Accuracy
Relative accuracy or endpoint nonlinearity is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function.
Differential Nonlinearity
This is the difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC.
Offset Error
This is the deviation of the first code transition (0000 . . . 000) to (0000 . . . 001) from the ideal, i.e., GND + 1 LSB.
Offset Error Match
This is the difference in Offset Error between any two channels.
Gain Error
This is the deviation of the last code transition (1111 . . . 110) to (1111 . . . 111) from the ideal, i.e., VREF – 1 LSB, after the offset error has been adjusted out.
Gain Error Match
This is the difference in gain error between any two channels.
Track/Hold Acquisition Time
Track/hold acquisition time is the time required for the output of the track/hold amplifier to reach its final value, within ±1/2 LSB, after the end of conversion (the point at which the track/ hold returns to track mode). It also applies to situations where
a change in the selected input channel takes place or where there is a step input change on the input voltage applied to the selected A
input of the AD7417 or AD7418. It means that
IN
the user must wait for the duration of the track/hold acquisi­tion time after the end of conversion or after a channel change/ step input change to A
before starting another conversion,
IN
to ensure that the part operates to specification.
CIRCUIT INFORMATION
The AD7417 and AD7418 are single- and four-channel, 15 µs conversion time, 10-bit A/D converters with on-chip tempera­ture sensor, reference and serial interface logic functions on a single chip. The AD7416 has no analog input channel and is intended for temperature measurement only. The A/D converter section consists of a conventional successive-approximation converter based around a capacitor DAC. The AD7416, AD7417, and AD7418 are capable of running on a 2.7 V to 5.5 V power supply and the AD7417 and AD7418 accept an analog input range of 0 V to +VREF. The on-chip temperature sensor allows an accurate measurement of the ambient device temperature to be made. The working measurement range of the temperature sensor is –55°C to +125°C. The parts require a 2.5 V reference which can be provided from the parts own internal reference or from an external reference source.

CONVERTER DETAILS

Conversion is initiated on the AD7417/AD7418 by pulsing the CONVST input. The conversion clock for the part is internally generated so no external clock is required except when reading from and writing to the serial port. The on-chip track/hold goes from track to hold mode and the conversion sequence is started on the falling edge of the CONVST signal. A conversion is also initiated in the automatic conversion mode every time a read or write operation to the AD7416/AD7417/AD7418 takes place. In this case, the internal clock oscillator (which runs the automatic conversion sequence) is restarted at the end of the read or write operation. The track/hold goes into hold approximately 3 µs after the read or write operation is complete and a conversion is then initiated. The result of the conversion is available either 15 µs or 30 µs later, depending on whether an analog input channel or the temperature sensor is selected. The track/hold acquisition time of the AD7417/AD7418 is 400 ns.
A temperature measurement is made by selecting the Channel 0 of the on-chip MUX and carrying out a conversion on this channel. A conversion on Channel 0 takes 30 µs to complete. Temperature measurement is explained in the Temperature Measurement section of this data sheet.
The on-chip reference is not available to the user, but REF
IN
can be overdriven by an external reference source (2.5 V only). The effect of reference tolerances on temperature measurements is discussed in the Reference section of the data sheet.
All unused analog inputs should be tied to a voltage within the nominal analog input range to avoid noise pickup. For mini­mum power consumption, the unused analog inputs should be tied to GND.
REV. D
–7–
Page 8
AD7416/AD7417/AD7418

TYPICAL CONNECTION DIAGRAM

Figure 2 shows a typical connection diagram for the AD7417. Using the A0, A1 and A2 pins allows the user to select from up to eight AD7417s on the same serial bus, if desired. An external
2.5 V reference can be connected at the REF
pin. If an exter-
IN
nal reference is used, a 10 µF capacitor should be connected between REF
2
I
C-compatible interface. For applications where power con-
and GND. SDA and SCL form the two-wire
IN
sumption is of concern, the automatic power-down at the end of a conversion should be used to improve power performance. See Operating Modes section of the data sheet.
SUPPLY
2.7V TO
OPTIONAL
EXTERNAL
REFERENCE
5.5V
0V TO 2.5V
INPUT
AD780/
REF-192
AIN1 AIN2 AIN3 AIN4
GND
0.1␮F10␮F
AD7417
REF
V
DD
CONVST
IN
10F FOR EXTERNAL REFERENCE
TWO-WIRE
SERIAL
INTERFACE
SCL SDA
OTI
A0 A1 A2
C/P
Figure 2. Typical Connection Diagram

ANALOG INPUTS

Figure 3 shows an equivalent circuit of the analog input struc­ture of the AD7417 and AD7418. The two diodes, D1 and D2, provide ESD protection for the analog inputs. Care must be taken to ensure that the analog input signal never exceeds the supply rails by more than 200 mV. This will cause these diodes to become forward-biased and start conducting current into the substrate. The maximum current these diodes can conduct without causing irreversible damage to the part, is 20 mA. The capacitor C2 in Figure 3 is typically about 4 pF and can prima­rily be attributed to pin capacitance. The resistor R1 is a lumped component made up of the on resistance of a multi­plexer and a switch. This resistor is typically about 1
k
. The capacitor C1 is the ADC sampling capacitor and has a capaci­tance of 3 pF.
V
DD
D1
A
IN
4pF
C2
D2
R1
1k
CONVERT PHASE – SWITCH OPEN TRACK PHASE – SWITCH CLOSED
C1
3pF
V
BALANCE
the REF
pin to analog ground. This causes SW1(see Figure
IN
4) to open and the reference amplifier to power up during a conversion. Therefore the on-chip reference is not available externally. An external 2.5 V reference can be connected to the REF
pin. This has the effect of shutting down the on-chip
IN
reference circuitry.
1.2V
REF
IN
1.2V
SW1
+
26k
24k
2.5V
EXTERNAL REFERENCE DETECT
+
BUFFER
Figure 4. On-Chip Reference

INTERNAL REGISTER STRUCTURE

The AD7417/AD7418 has seven internal registers, as shown in Figure 5. Six of these are data registers and one is an address pointer register. The AD7416 has five internal registers (the ADC and Config2 registers are not applicable to the AD7416).
TEMPERATURE
VALUE
REGISTER
(READ-ONLY
ADDRESS 00H)
CONFIGURATION
REGISTER
(READ/WRITE
ADDRESS 01H)
T
SET-POINT
HYST
REGISTER
(READ/WRITE
ADDRESS 02H)
SET-POINT
T
OTI
REGISTER
(READ/WRITE
ADDRESS 03H)
ADDRESS POINTER
REGISTER
(SELECTS DATA REGISTER
FOR READ/WRITE)
ADDRESS
INTERFACE
REGISTER
(READ ONLY
ADDRESS 04H)
CONFIG 2
REGISTER
(READ/WRITE
ADDRESS 05H)
SERIAL
BUS
ADC
DATA
SDA SCL
Figure 5. AD7417/AD7418 Register Structure
Figure 3. Equivalent Analog Input Circuit

ON-CHIP REFERENCE

The AD7416/AD7417/AD7418 has an on-chip 1.2 V band-gap reference which is gained up by a switched capacitor amplifier to give an output of 2.5 V. The amplifier is only powered up at the start of the conversion phase and is powered down at the end of the conversion. The on-chip reference is selected by connecting
–8–

ADDRESS POINTER REGISTER

The Address Pointer Register is an 8-bit register which stores an address that points to one of the six data registers. The first data byte of every serial write operation to the AD7416/AD7417/ AD7418 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 three LSBs of this register are used to select a data register.
REV. D
Page 9
AD7416/AD7417/AD7418
Table I. Address Pointer Register
P7
*
P6
*
P5
*
P4*P3
*
P2 P1 P0
00000 Register Select
*P3 to P7 must be set to 0.
Table II. Register Addresses
P2 P1 P0 Registers
000Temperature Value (Read Only) 001Config Register (Read/Write) 010T 011T
(Read/Write)
HYST
OTI
1 0 0 ADC (AD7417/AD7418 Only) 101Config2 (AD7417/AD7418 Only)
TEMPERATURE VALUE REGISTER (ADDRESS 00H)
The temperature value register is a 16-bit, read-only register whose 10 MSBs store the temperature reading from the ADC in 10-bit twos complement format. Bits 5 to 0 are unused.
Table III. Temperature Value Register
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6
MSB B8 B7 B6 B5 B4 B3 B2 B1 LSB
The temperature data format is shown in Table IV. This shows the full theoretical range of the ADC from –128°C to +127°C, but in practice the temperature measurement range is limited to the operating temperature range of the device.
Table IV. Temperature Data Format
Table V. Configuration Register
D7 D6 D5 D4 D3 D2 D1 D0
Channel Fault OTI Cmp/ Shut­Selection Queue Polarity Int down
The AD7416 contains a temperature-only channel, the AD7417 has four analog input channels and a temperature channel, while the AD7418 has two channels, a temperature channel and an analog input channel. The temperature channel address for all parts is the same, CH0. The address for the analog input channel on the AD7418 is CH4. Table VI outlines the channel selection on the parts, while Table VII shows the fault queue settings. D1 and D2 are explained in the OTI Output section.
Table VI. Channel Selection
D7 D6 D5 Channel Selection
0 0 0 Temperature Sensor (All Parts) 0 0 1 AIN1 (AD7417 Only) 0 1 0 AIN2 (AD7417 Only) 0 1 1 AIN3 (AD7417 Only) 1 0 0 AIN4 (AD7417) and AIN (AD7418)
Table VII. Fault Queue Settings
D4 D3 Number of Faults
0 0 1 (Power-Up Default) 012 104 116
Temperature Digital Output
128°C 10 0000 0000125°C 10 0000 1100100°C 10 0111 000075°C 10 1101 010050°C 11 0011 100025°C 11 1001 11000.25°C 11 1111 1111
0°C 00 0000 0000 +0.25°C 00 0000 0001 +10°C 00 0010 1000 +25°C 00 0110 0100 +50°C 00 1100 1000 +75°C 01 0010 1100 +100°C 01 1001 0000 +125°C 01 1111 0100 +127°C 01 1111 1100

CONFIGURATION REGISTER (ADDRESS 01H)

The Configuration Register is an 8-bit, read/write register that is used to set the operating modes of the AD7416/AD7417/ AD7418. Bits D7 to D5 control the channel selection as out­lined in Table VI. These bits should always be 0,0,0 for the AD7416. Bits D4 and D3 are used to set the length of the fault queue. D2 sets the sense of the OTI output. D1 selects com­parator or interrupt mode of operation, and D0 = 1 selects shutdown mode (Default D0 = 0).
T
SETPOINT REGISTER (ADDRESS 02H)
HYST
The T whose 9 MSBs store the T
Setpoint Register is a 16-bit, read/write register
HYST
setpoint in twos complement
HYST
format equivalent to the 9 MSBs of the temperature value regis­ter. Bits 6 to 0 are unused.
T
SETPOINT REGISTER (ADDRESS 03H)
OTI
The T 9 MSBs store the T
Setpoint Register is a 16-bit, read/write register whose
OTI
setpoint in twos complement format
OTI
equivalent to the 9 MSBs of the temperature value register. Bits 6 to 0 are unused.
Table VIII. Setpoint Registers
D15 D14 D13 D12 D11 D10 D9 D8 D7
MSB B7 B6 B5 B4 B3 B2 B1 LSB

ADC VALUE REGISTER (ADDRESS 04H)

The ADC value register is a 16-bit, read only register whose 10 MSBs store the value produced by the ADC in binary for­mat. Bits 5 to 0 are unused. Table IX shows the ADC value register with 10 MSBs containing the ADC conversion request.
Table IX.
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6
MSB B8 B7 B6 B5 B4 B3 B2 B1 LSB
REV. D
–9–
Page 10
AD7416/AD7417/AD7418
ADC Transfer Function
The designed code transitions occur at successive integer LSB values (i.e., 1 LSB, 2 LSB, etc.). The LSB size is = REF/1024. The ideal transfer function characteristic for the AD7417 and AD7418 ADC is shown in Figure 6.
111...111
111...110
111...000
011...111
ADC CODE
000...010
000...001
000...000
0V 1/2LSB +V
1LSB = V
ANALOG INPUT
REF
REF
– 1LSB
/1024
Figure 6.
CONFIG2 REGISTER (ADDRESS 05H)
A second configuration register is included in the AD7417/ AD7418 for the functionality of the CONVST pin. It is an 8-bit register with bits D5 to D0 being left at 0. Bit D7 determines whether the AD7417/AD7418 should be operated in its default mode (D7 = 0), performing conversions every 355 µs or in CONVST pin mode (D7 = 1), where conversions will start only when the CONVST pin is used. Bit 6 contains the Test 1 bit. When this bit is 0 the I
2
C filters are enabled (default). A 1
disables the filters.
Table X.
D7 D6 D5 D4 D3 D2 D1 D0
Conversion Mode Test 1 000000

SERIAL BUS INTERFACE

Control of the AD7416/AD7417/AD7418 is carried out via the
2
C-compatible serial bus. The AD7416/AD7417/AD7418 is
I connected to this bus as a slave device, under the control of a master device, e.g., the processor.

SERIAL BUS ADDRESS

As with all I2C-compatible devices, the AD7416/AD7417/AD7418 have a 7-bit serial address. The four MSBs of this address for the AD7416 are set to 1001, the AD7417 are 0101, while the three LSBs can be set by the user by connecting the A2 to A0 pins to either +V
or GND. By giving them different addresses,
S
up to eight AD7416/AD7417s can be connected to a single serial bus, or the addresses can be set to avoid conflicts with other devices on the bus. The four MSBs of this address for the AD7418 are 0101, while the three LSBs are all set to zero.
If a serial communication occurs during a conversion operation, the conversion will stop and will restart after the communication.
The serial bus protocol operates as follows:
1. 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 will follow. 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 a R/W bit, which deter­mines the direction of the data transfer, i.e., whether data will be 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 now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is a 0 then the master will write to the slave device. If the R/W bit is a 1 the master will read from the slave device.
2. 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, as a low-to-high transition when the clock is high may be interpreted as a STOP signal.
3. When all data bytes have been read or written, stop condi­tions are established. In WRITE mode, the master will pull the data line high during the 10th clock pulse to assert a STOP condition. In READ mode, the master device will pull the data line high during the low period before the 9th clock pulse. This is known as No Acknowledge. The master will then take 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, because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation.
–10–
REV. D
Page 11
AD7416/AD7417/AD7418

WRITING TO THE AD7416/AD7417/AD7418

Depending on the register being written to, there are three dif­ferent writes for the AD7416/AD7417/AD7418.
1. 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 7. 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.
2. Writing a single byte of data to the Configuration Registers or T
, T
OTI
Registers.
HYST
The Configuration Register is an 8-bit register, so only one byte of data can be written to it. If only 8-bit temperature
191
SCL
1
SDA
START BY
MASTER
001A2
FRAME 1
SERIAL BUS ADDRESS BYTE
A0
A1
R/W
ACK. BY
AD7416
comparisons are required, the temperature LSB can be ignored in T T
OTI
and T
OTI
and T
, and only eight bits need be written to the
HYST
registers.
HYST
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 8.
3. Writing two bytes of data to the T
OTI
or T
If 9-bit resolution is required for the temperature setpoints, then two bytes of data must be written to the T T
registers. This consists of the serial bus address, the
HYST
register address, written to the address pointer register, fol­lowed by two data bytes written to the selected data register. This is illustrated in Figure 9.
9
P6
P7
P5 P4
ADDRESS POINTER REGISTER BYTE
P3
FRAME 2
P1
P2
P0
ACK. BY
AD7416
Figure 7. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation
HYST
STOP BY
MASTER
Register.
and
OTI
SCL
SDA
START BY
MASTER
19
001A2 A1 A0 P7 P 6 P5
1
FRAME 1
SERIAL BUS ADDRESS BYTE
SCL (CONTINUED)
SDA (CONTINUED)
R/W
ACK. BY
AD7416
1
P3 P2 P1 P0
P4
ADDRESS POINTER REGISTER BYTE
19
D6 D5
D7
D4
FRAME 2
D3 D2 D1 D0
FRAME 3
DATA BYTE
ACK. BY
AD7416
9
ACK. BY
AD7416
STOP BY MASTER
Figure 8. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register
REV. D
–11–
Page 12
AD7416/AD7417/AD7418
READING DATA FROM THE AD7416/AD7417/AD7418
Reading data from the AD7416/AD7417/AD7418 is a one or two byte operation. Reading back the contents of the Configura­tion Register is a single byte read operation, as shown in Figure 10, the register address previously having been set by a single­byte write operation to the address pointer register.
Reading data from the temperature value, T
OTI
, or T
HYST
regis-
ters is a two-byte operation, as shown in Figure 11. It is also
OTI OUTPUT
The OTI output has two operating modes, which are selected by Bit D1 of the Configuration Register. In the comparator mode, (D1 = 0), the OTI output becomes active when the temperature exceeds T below T
, and remains active until the temperature falls
OTI
. This mode allows the AD7416/AD7417/AD7418
HYST
to be used as a thermostat, for example to control the operation of a cooling fan.
possible to read the most significant bit of a 9-/10-bit register in this manner.
191
SCL
SDA 0 0
START BY
MASTER
SCL
(CONTINUED)
SDA
(CONTINUED)
1
SERIAL BUS ADDRESS BYTE
19
D15 D14
A2
1
FRAME 1
D12 D11
D13
MOST SIGNIFICANT DATA BYTE
FRAME 3
A0
A1
D10
D9
R/W
ACK. BY
AD7416
D8
ACK. BY
AD7416
P6
P7
19
D7 D6
STOP BY MASTER
P4 P3 P2 P1 P0
P5
ADDRESS POINTER REGISTER BYTE
FRAME 2
D4 D3
D5
LEAST SIGNIFICANT DATA BYTE
FRAME 4
Figure 9. Writing to the Address Pointer Register Followed by a Two Bytes of Data to the T
D2
D1
ACK. BY
AD7416
D0
or T
OTI
9
ACK. BY
AD7416
HYST
STOP BY MASTER
Register
SCL
SDA
START BY
MASTER
SCL
SDA
START BY
MASTER
191 9
0
FRAME 1
SERIAL BUS ADDRESS BYTE
A0A1A2101
R/W
ACK. BY
D7 D6 D5 D4 D3 D2 D1 D0
AD7416
SINGLE DATA BYTE FROM AD7416
FRAME 2
NO ACK. BY
MASTER
STOP BY
MASTER
Figure 10. Reading a Single Byte of Data from the Configuration Register
19
0 0 1 A2 A1 A0 D15 D14 D13
1
FRAME 1
SERIAL BUS ADDRESS BYTE
SCL (CONTINUED)
SDA (CONTINUED)
R/W
ACK. BY
AD7416
Figure 11. Reading Two Bytes of Data from T
1
D10 D11 D9 D8
D12
MOST SIGNIFICANT DATA BYTE FROM AD7416
19
D6 D5
D7
LEAST SIGNIFICANT DATA BYTE FROM AD7416
D4
OTI
FRAME 2
D3 D2 D1 D0
FRAME 3
or T
HYST
Register
NO ACK. BY
MASTER
9
ACK. BY MASTER
STOP BY
MASTER
–12–
REV. D
Page 13
AD7416/AD7417/AD7418
T
OTI
T
HYST
OTI OUTPUT
COMPARATOR
MODE
OTI OUTPUT
INTERRUPT
MODE
*
IN INTERRUPT MODE, A READ OPERATION OR SHUTDOWN RESETS THE OTI OUTPUT; OTHERWISE THE OTI OUTPUT REMAINS ACTIVE INDEFINITELY, ONCE TRIGGERED.
READ* READ* READ* READ* READ* READ* READ*
Figure 12. Operation of OTI Output (Shown Active Low)
The open-drain configuration of OTI allows the OTI outputs of several AD7416/AD7417/AD7418s to be wire-ANDed together when in active low mode.
The OTI output is used to indicate that an out-of-limit tem­perature excursion has occurred. OTI is an open-drain output that can be programmed to be active low by setting Bit D2 of the Configuration Register to 0, or active high by setting Bit D2 of the Configuration Register to 1.
In the Interrupt mode (D1 = 1), the OTI output becomes active when the temperature exceeds T the temperature falls below T
HYST
, and remains active even if
OTI
, until it is reset by a read opera­tion. Once OTI has become active by the temperature exceeding T
, then been reset, it will remain inactive even if the tempera-
OTI
ture remains, or subsequently rises again, above T become active again until the temperature falls below T
. It will not
OTI
HYST
. It will then remain active until reset by a read operation. Once OTI has become active by the temperature falling below T
HYST
, then been reset, it will remain inactive even if the temperature remains, or subsequently falls again, below T
HYST
.
OTI is also reset when the AD7416/AD7417/AD7418 is placed in shutdown mode, by setting bit D0 of the Configuration Regis­ter to 1.
The OTI output requires an external pull-up resistor. This can be connected to a voltage different from +V
(for example, to
S
allow interfacing between 5 V and 3.3 V systems) provided that the maximum voltage rating of the OTI output is not exceeded.
The value of the pull-up resistor depends on the application, but should be as large as possible to avoid excessive sink currents at the OTI output, which can heat the chip and affect the tempera­ture reading. The maximum value of pull-up resistor that will meet the output high current specification of the OTI output is 30 k, but higher values may be used if a lower output current is required. For most applications a value of 10 k will prove suitable.

FAULT QUEUE

To avoid false triggering of the AD7416/AD7417/AD7418 in noisy environments, a fault queue counter is provided, which can be programmed by Bits D3 and D4 of the Configuration Register (see Table V) to count 1, 2, 4, or 6 fault events before OTI becomes active. In order to trigger OTI, the faults must occur consecutively. For example, if the fault queue is set to 4, then four consecutive temperature measurements greater than
(or less than T
T
OTI
) must occur. Any reading that breaks
HYST
the sequence will reset the fault queue counter, so if there are three readings greater than T T
, the fault queue counter will be reset without triggering OTI.
OTI
REV. D
followed by a reading less than
OTI
–13–

POWER-ON DEFAULTS

The AD7416/AD7417/AD7418 always powers up with the following defaults:
Address pointer pointing to Temperature Value Register Comparator mode:
T
= 80°C
OTI
T
= 75°C
HYST
OTI Active LOW Fault Queue = 1
These default settings allow the AD7416/AD7417/AD7418 to be used as a stand-alone thermostat without any connection to a serial bus.

OPERATING MODES

The AD7416/AD7417/AD7418 has two possible modes of operation depending on the value of D0 in the Configuration Register.
Mode 1
Normal operation of the AD7416/AD7417/AD7418 occurs when D0 = 0. In this active mode, a conversion takes place every 400 µs. Once the conversion has taken place, the part partially powers down, consuming typically 350 µA of current until the next conversion occurs.
Two situations can arise in this mode on the request of a temperature read. If a read occurs during a conversion, the conversion
aborts and a new one starts on the Stop/Repeat start condition. The temperature value that is read is that of the previous completed conversion. The next conversion will typically occur 400 µs after the new conversion has begun.
If a read is called between conversions, a conversion is initiated on the stop/repeat start condition. After this conversion, the part returns to performing a conversion every 400 µs.
With a V
= 3 V, for each 400 µs cycle, the AD7416 spends
DD
40 µs (or 10% of the time) in conversion mode. It spends 360 µs (or 90% of time) in partial power-down mode. Thus the average power dissipated by the AD7416/AD7417/AD7418 is:
3 mW × 0.1 + 1 mW × 0.9 = 1.2 mW
Mode 2
For applications where temperature measurements are required at a slower rate e.g., every second, power consumption of the part can be reduced by writing to the part to go to a full power-down between reads. The current consumption in full power-down is typically 0.2 µA and full power-down is initiated when D0 = 1 in the configuration register. When a measurement is required, a write operation can be performed to power-up the part. The part then performs a conversion and is returned to power-down. The temperature value can be read in the full power-down because the I
2
C bus is continuously active.
The power dissipation in this mode depends on the rate at which reads take place. Taking the requirements for a tempera­ture measurement every 100 ms as an example, the optimum power dissipation is achieved by placing the part in full power­down, waking it up every 100 ms, letting it operate for 400 µs and putting it into full power-down again. In this case the aver­age power consumption is calculated as follows. The part spends 40 µs (or 0.04% of time) converting with 3 mW dissipation, and a 99.96 ms (99.96% of time) in full shutdown with 60 nW dissi­pation. Thus the average power dissipation is:
3 mW × 0.004 + 60 nW × 0.9996 = 1.2
µ
W
Page 14
AD7416/AD7417/AD7418
The fastest throughput rate at which the AD7416/AD7417/ AD7418 can be operated is 2.5 kHz (i.e., a read every 400 µs conversion period). Since T the read time with the I
and T
OTI
2
C operating at 100 kbit/s would be
are two byte reads,
HYST
270 µs. If temperature reads are called too often, reads will overlap with conversions, aborting them continuously, which results in invalid readings.

CONVERT START MODE

The AD7417/AD7418 has an extra mode, set by writing to the MSB of the Config2 Register.
CONVST Pin Mode
By setting the CONVST mode bit to 1, conversions are initiated only by using the CONVST pin. In this method of operation, CONVST is normally low.
The rising edge of CONVST starts the power-up time. This power-up time is 4 µs. If the CONVST high time is longer than 4 µs, a conversion is initiated on the falling edge of CONVST and the track/hold also enters its hold mode at this time. If the CONVST high time is less than 4 µs, an internal timer, initi- ated by the rising edge of CONVST holds off the track/hold and the initiation of conversion until timer times out (4 µs after the rising edge of CONVST, which corresponds with the power-up time). CONVST input remains low at the end of conversion, thus causing the part to enter its power-down mode. In this method of operation, CONVST is normally low with a high-going pulse controlling the power-up and conversion starts.
The CONVST pin should not be pulsed when reading from or writing to the port.
Figure 16 shows the recommended minimum times for the CONVST pulse when the temperature channel is selected. Figure 17 shows the minimum times an analog input channel is selected.

MOUNTING THE AD7416

The AD7416/AD7417/AD7418 can be used for surface or air­temperature sensing applications. If the device is cemented to a surface with thermally conductive adhesive, the die temperature will be within about 0.2°C of the surface temperature, thanks to the devices 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 will be 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 AD7416/AD7417/AD7418 and its 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 AD7416 package allows it to be mounted inside sealed metal probes, which provide a safe environment for the device.

FAN CONTROLLER

Figure 13 shows a simple fan controller that will switch on a cooling fan when the temperature exceeds 80°C, and switch it off again when the temperature falls below 75°C. The AD7416 can be used stand-alone in this application, or with a serial bus interface if different trip temperatures are required. If the AD7416 is used with a bus interface, the sense of OTI can be set to active high, Q1 and R1 can be omitted, and OTI connected directly to the gate of Q2, with R2 as the pull-up resistor.
12V
APPLICATIONS INFORMATION SUPPLY DECOUPLING
The AD7416/AD7417/AD7418 should be decoupled with a
0.1 µF ceramic capacitor between +V
and GND. This is
S
particularly important if the part is mounted remote from the power supply.

POWER-ON-RESET

To ensure proper power-on-reset, make sure that the supply voltage on the V
pin is at 0 V. Reference application note
DD
AN-588 for more information.
+V
S
3V TO 5.5V
Q2 LOGIC LEVEL MOSFET RATED TO SUIT FAN CURRENT
AD7416
R1 10k
R2 10k
Q1 2N3904 OR SIMILAR
Figure 13. AD7416 Used as a Fan Controller
–14–
REV. D
Page 15
AD7416/AD7417/AD7418
C
THERMOSTAT
Figure 14 shows the AD7416 used as a thermostat. The heater will be switched on when the temperature falls below T and switched off again when the temperature rises above T
HYST
OS
,
. For this application, the OTI output should be programmed active low, and for comparator mode.
+V
S
3V TO 5.5V
AD7416
R1 10k
RELAY
Q1 2N3904 OR SIMILAR
D1 1N4001
HEATER
RLA1
HEATER SUPPLY
Figure 14. AD7416 Used as a Thermostat
+V
S
3V TO 5.5V
R1 10k
SYSTEM WITH MULTIPLE AD7416s
The three LSBs of the AD7416s serial address can be set by the user, allowing eight different addresses from 1001000 to
1001111. Figure 15 shows a system in which eight AD7416s are connected to a single serial bus, with their OTI outputs wire ANDed together to form a common interrupt line. This arrange­ment does mean that each device must be read to determine which one has generated the interrupt, and if a unique interrupt is required for each device, the OTI outputs can be connected separately to the I/O chip.
CONVST
Figure 16.
AD7416
CONVST
AD7416
AD7416
Figure 15. Multiple Connection of AD7416s to a Single Serial Bus
100ns
40s
When Temperature Channel Selected
AD7416
AD7416
Figure 17.
ONVST
AD7416
100ns
CONVST
AD7416
15s
When V
AD7416
Channel(s) Selected
IN
SUPER I/O CHIP
PROCESSOR
REV. D
–15–
Page 16
AD7416/AD7417/AD7418
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
0.1574 (4.00)
0.1497 (3.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
0.1574 (4.00)
0.1497 (3.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
16-Lead Narrow Body (SOIC)
(R-16A)
0.3937 (10.00)
0.3859 (9.80)
16 9
PIN 1
0.0500
0.0192 (0.49)
(1.27)
0.0138 (0.35)
BSC
0.2440 (6.20)
81
0.2284 (5.80)
0.0688 (1.75)
0.0532 (1.35)
0.0099 (0.25)
0.0075 (0.19)
8-Lead Narrow Body (SOIC)
(R-8)
0.1968 (5.00)
0.1890 (4.80)
85
PIN 1
0.0500 (1.27)
BSC
0.2440 (6.20)
41
0.2284 (5.80)
0.0688 (1.75)
0.0532 (1.35)
0.0192 (0.49)
0.0138 (0.35)
0.0098 (0.25)
0.0075 (0.19)
0.0196 (0.50)
0.0099 (0.25)
8° 0°
0.0500 (1.27)
0.0160 (0.41)
0.0196 (0.50)
0.0099 (0.25)
8° 0°
0.0500 (1.27)
0.0160 (0.41)
x 45°
x 45°
16-Lead Thin Shrink Small Outline Package
(TSSOP) (RU-16)
0.201 (5.10)
0.193 (4.90)
16 9
0.177 (4.50)
0.006 (0.15)
0.002 (0.05)
SEATING
PLANE
0.169 (4.30)
1
PIN 1
0.0256 (0.65)
BSC
0.0118 (0.30)
0.0075 (0.19)
8
0.256 (6.50)
0.246 (6.25)
0.0433 (1.10) MAX
0.0079 (0.20)
0.0035 (0.090)
8° 0°
0.028 (0.70)
0.020 (0.50)
8-Lead SOIC Package
(RM-8)
0.122 (3.10)
0.114 (2.90)
0.122 (3.10)
0.114 (2.90)
0.006 (0.15)
0.002 (0.05)
SEATING
PLANE
85
PIN 1
0.0256 (0.65) BSC
0.120 (3.05)
0.112 (2.84)
0.018 (0.46)
0.008 (0.20)
0.199 (5.05)
0.187 (4.75)
41
0.043 (1.09)
0.037 (0.94)
0.011 (0.28)
0.003 (0.08)
0.120 (3.05)
0.112 (2.84)
33 27
C01126–0–2/02(D)
0.028 (0.71)
0.016 (0.41)
Revision History
Location Page
Data Sheet changed from REV. C to REV. D.
Edits to SPECIFICATIONS headings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Edits to SERIAL BUS ADDRESS section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Edits to Figure 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Edits to CONVST Pin Mode section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Addition of two new figures (16 and 17) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
–16–
REV. D
PRINTED IN U.S.A.
Loading...