EVAL-AD7416/7/8EBZ - Analog Devices

10-Bit Digital Temperature Sensor

(AD7416) and Four Single-Channel ADCs

AD7416/AD7417/AD7418

Rev. I

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

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FEATURES

10-bit ADC with 15 μs and 30 μs conversion times

Single and 4 single-ended analog input channels

On-chip temperature sensor: −40°C to +125°C

On-chip track-and-hold

Overtemperature indicator

Automatic power-down at the end of a conversion

Wide operating supply range: 2.7 V to 5.5 V

I2C-compatible serial interface

Selectable serial bus address allows connection of up to 8

AD7416/AD7417 devices 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-channel and single-channel

ADCs 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-and-hold, and a

reference (2.5 V). The AD7416 is a temperature-monitoring only

device in an 8-lead package.

The temperature sensor on the parts can be accessed via multip-

lexer 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 tempera-

ture limits, and an open-drain overtemperature 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.

FUNCTIONAL BLOCK DIAGRAMS

SETPOINT

COMPARATOR

10-BIT

ANALOG-TO-DIGITAL

CONVERTER

AD7416

BAND GAP

TEMPERATURE

SENSOR

ADDRESS

POINTER

TEMPERATURE

VALUE

CONFIGURATION

SERIAL BUS

INTERFACE

FAULT

QUEUE

COUNTER

OTI

SETPOINT

HYST

SETPOINT

GND

OTI

SDA

SCL

01126-001

Figure 1. AD7416

AD7417

12 11

NC = NO CONNECT

GND

CONVST

TEMP

SENSOR

MUX

REF

2.5V

SAMPLING

CAPACITOR

CLOCK

OTI

SETPOINT

DATA OUT

INTERFACE

CONTROL

LOGIC

IN1

IN2

IN3

IN4

BALANCE

OTI

REF

SCL

SDA

A1 A2

01126-002

CHARGE

DISTRIBUTION

DAC

Figure 2. AD7417

AD7418

GND

CONVST

TEMP

SENSOR

MUX

REF

2.5V

SAMPLING

CAPACITOR

CLOCK

OTI

SETPOINT

DATA OUT

INTERFACE

CONTROL

LOGIC

BALANCE

OTI

REF

SCL

SDA

01126-003

CHARGE

DISTRIBUTION

DAC

Figure 3. AD7418

AD7416/AD7417/AD7418

Rev. I | Page 2 of 24

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications....................................................................................... 1

General Description......................................................................... 1

Functional Block Diagrams............................................................. 1

Revision History ............................................................................... 2

Product Highlights ........................................................................... 3

Specifications..................................................................................... 4

AD7417/AD7418 Specifications................................................. 4

AD7416 Specifications................................................................. 6

Absolute Maximum Ratings............................................................ 7

ESD Caution.................................................................................. 7

Pin Configurations and Function Descriptions ........................... 8

Terminology .................................................................................... 10

Theory of Operation ...................................................................... 11

Circuit Information.................................................................... 11

Converter Details........................................................................ 11

Typical Connection Diagram ................................................... 11

Analog Inputs.............................................................................. 11

On-Chip Reference .................................................................... 11

Temperature Measurement....................................................... 12

Internal Register Structure........................................................ 12

Serial Bus Interface..................................................................... 14

OTI Output ................................................................................. 17

Fault Queue ................................................................................. 17

Power-On Defaults..................................................................... 17

Operating Modes........................................................................ 17

CONVST Start Mode................................................................. 18

Applications Information.............................................................. 19

Supply Decoupling ..................................................................... 19

Power-On Reset.......................................................................... 19

Mounting the AD7416/AD7417/AD7418 .............................. 19

Fan Controller............................................................................. 19

Thermostat.................................................................................. 19

System with Multiple AD7416 Devices................................... 20

Outline Dimensions ....................................................................... 21

Ordering Guide .......................................................................... 23

REVISION HISTORY

11/10—Rev. H to Rev. I

Changes to Figure 19...................................................................... 16

2/09—Rev. G to Rev. H

Updated Format..................................................................Universal

Changes to Data Sheet Title, Figure 2 and Figure 3..................... 1

Moved Product Highlights Section................................................ 3

Changes to Table 1............................................................................ 4

Changes to Endnote 1, Table 2........................................................ 6

Added Figure 5 Caption................................................................... 7

Changes to Table 4............................................................................ 8

Changes to Table 5 and Table 6....................................................... 9

Changes to On-Chip Reference Section...................................... 11

Changes to Figure 13...................................................................... 12

Changes to Table 8 and Table 10................................................... 13

Changes to Figure 15, Figure 16, and Figure 17 ......................... 15

Changes to Reading Data From the AD7416/AD7417/AD7418

Section, Figure 18, and Figure 19 ................................................. 16

Change to Mode 1 .......................................................................... 17

Changes to Figure 22 Caption and CONVST Pin Mode

Section.............................................................................................. 18

Moved Figure 21 and Figure 22 .................................................... 18

Changes to Power-On Reset Section............................................ 19

Updated Outline Dimensions....................................................... 21

Changes to Ordering Guide .......................................................... 23

8/04—Data Sheet Changed from Rev. F to Rev. G

Changes to Figure 12...................................................................... 12

Changes to Reading Data from the AD7416/AD7417/AD7418

Section.............................................................................................. 13

Changes to Power-On-Reset section ........................................... 14

7/03—Data Sheet Changed from Rev. E to Rev. F

Updated Features...............................................................................1

Updated Specifications .....................................................................3

Updated Absolute Maximum Ratings ............................................6

Updated Ordering Guide .................................................................6

Updated Product Highlights............................................................7

Updated Circuit Information...........................................................7

Updated Temperature Measurement section ................................9

10/02—Data Sheet Changed from Rev. D to Rev. E

Edits to Specifications Headings .....................................................2

Added Temperature Measurement section....................................8

Edits to Serial Bus Address section .............................................. 10

Edits to Figure 11............................................................................ 12

Edits to CONVST Pin Mode section ........................................... 14

Edits to Power-On-Reset section ................................................. 14

Addition of Figures 16 and 17 ...................................................... 15

Updated Outlines ........................................................................... 16

AD7416/AD7417/AD7418

Rev. I | Page 3 of 24

An I2C® compatible serial interface allows the AD7416/AD7417/

AD7418 registers to be written to and read back. The three

LSBs of the AD7416/AD7417 serial bus address can be selected,

which allows up to eight AD7416/AD7417 devices to be connected

to a single bus.

The AD7417 is available in a narrow body, 0.15 inch, 16-lead,

small outline package (SOIC) and in a 16-lead, thin shrink,

small outline package (TSSOP). The AD7416 and AD7418 are

available in 8-lead SOIC and MSOP 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 overtemperature) to be

made. The measurable temperature range is −40°C to

+125°C. An overtemperature 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 TOTI setpoint register.

2. The AD7417 offers a space-saving, 10-bit analog-to-digital

solution with four external voltage input channels, an on-

chip temperature sensor, an on-chip reference, and a 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.

AD7416/AD7417/AD7418

Rev. I | Page 4 of 24

SPECIFICATIONS

AD7417/AD7418 SPECIFICATIONS

VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted.

Table 1.

Parameter A Version B Version1 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 Accuracy2 ±1 ±1 LSB max This specification is typical for VDD of 3.6 V to 5.5 V

Differential Nonlinearity2 ±1 ±1 LSB max This specification is typical for VDD of 3.6 V to 5.5 V

Gain Error2 ±3 ±3 LSB max External reference

±10 ±10 LSB max Internal reference

Gain Error Match2 ±0.6 ±0.6 LSB max AD7417 only

Offset Error2 ±4 ±4 LSB max

Offset Error Match2 ±0.7 ±0.7 LSB max AD7417 only

ANALOG INPUTS

Input Voltage Range VREF VREF V max

0 0 V min

Input Leakage Current3 ±1 ±1 A max

Input Capacitance 10 10 pF max

TEMPERATURE SENSOR1

Measurement Error

Ambient Temperature 25°C ±2 ±1 °C max

TMIN to TMAX ±3 ±2 °C max

Temperature Resolution 1/4 1/4 °C/LSB

CONVERSION RATE

Track-and-Hold Acquisition Time4 400 400 ns max Source impedance < 10 Ω

Conversion Time

Temperature Sensor 30 30 s max Typically 27 s

Channel 1 to Channel 4 15 15 s max Typically 10 s

REFERENCE INPUT5,6

REFIN Input Voltage Range 2.625 2.625 V max 2.5 V + 5%

2.375 2.375 V min 2.5 V − 5%

Input Impedance 40 40 kΩ min

Input Capacitance 10 10 pF max

ON-CHIP REFERENCE Nominal 2.5 V

Reference Error6 ±25 ±25 mV max

Temperature Coefficient6 80 80 ppm/°C typ

DIGITAL INPUTS

Input High Voltage, VIH VDD × 0.7 VDD × 0.7 V min

Input Low Voltage, VIL VDD × 0.3 VDD × 0.3 V max

Input Leakage Current 1 1 A max

DIGITAL OUTPUTS

Output Low Voltage, VOL 0.4 0.4 V max IOL = 3 mA

Output High Current 1 1 A max VOH = 5 V

AD7416/AD7417/AD7418

Rev. I | Page 5 of 24

Parameter A Version B Version1 Unit Test Conditions/Comments

POWER REQUIREMENTS

VDD 5.5 5.5 V max For specified performance

2.7 2.7 V min

IDD Logic inputs = 0 V or VDD

Normal Operation 600 600 A max

Power-Down 1.5 1.5 A max 0.7 µA typically

Auto Power-Down Mode VDD = 3 V; see the Operating Modes section

10 SPS Throughput Rate 6 6 W typ

1 kSPS Throughput Rate 60 60 W typ

10 kSPS Throughput Rate 600 600 W typ

Power-Down 3 3 W max Typically 0.15 W

1 B Version applies to AD7417 only with temperature range of −40°C to +85°C. A Version temperature range is −40°C to +125°C. For VDD = 2.7 V, TA = 85°C maximum and

temperature sensor measurement error = ±3°C maximum.

2 See the Terminology section.

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 an external reference is applied.

6 The accuracy of the temperature sensor is affected by reference tolerance.

AD7416/AD7417/AD7418

Rev. I | Page 6 of 24

AD7416 SPECIFICATIONS

VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted.

Table 2.

Parameter Min Typ Max Unit Test Conditions/Comments

TEMPERATURE SENSOR AND ADC

Accuracy ±2.0 °C TA = −25°C to + 100°C

DD = 3 V minimum)1

±3.0 °C TA = −40°C to + 125°C

DD = 3 V minimum)1

Resolution 10 Bits

Temperature Conversion Time 40 s

Update Rate, tR 400 s

OTI Delay 1 × tR 6 × tR ms Depends on fault queue setting

Supply Current 1.0 mA I2C active

350 600 A I2C inactive

0.2 1.5 A Shutdown mode

TOTI Default Temperature 80 °C

THYST Default Temperature 75 °C

DIGITAL INPUTS

Input High Voltage, VIH VDD × 0.7 VDD + 0.5 V

Input Low Voltage, VIL −0.3 VDD × 0.3 V

Input High Current, IIH +0.005 +1.0 A VIN = 5 V

Input Low Current, IIL −0.005 −1.0 A VIN = 0 V

Input Capacitance, CIN 20 pF All digital inputs

DIGITAL OUTPUTS

Output Low Voltage, VOL 0.4 V IOL = 3 mA

Output High Current 1 A VOH = 5 V

Output Fall Time, tf 250 ns CL = 400 pF, IO = 3 mA

OS Output Low Voltage, VOL 0.8 V IOUT = 4 mA

AC ELECTRICAL CHARACTERISTICS2 AD7416/AD7417/AD7418

Serial Clock Period, t1 2.5 s See Figure 4

Data In Setup Time to SCL High, t2 50 ns See Figure 4

Data Out Stable after SCL Low, t3 0 ns See Figure 4

SDA Low Setup Time to SCL Low

(Start Condition), t4 50 ns See Figure 4

SDA High Hold Time after SCL High

(Stop Condition), t5 50 ns See Figure 4

SDA and SCL Fall Time, t6 300 ns See Figure 4

1 For VDD = 2.7 V to 3 V, TA maximum = 85°C and temperature sensor measurement error = ±3°C maximum.

2 Sample tested during initial release and after any redesign or process change that may affect this parameter.

SCL

t4t2t5

SDA

DATA IN

SDA

DATA OUT

01126-004

Figure 4. Diagram for Serial Bus Timing

AD7416/AD7417/AD7418

Rev. I | Page 7 of 24

ABSOLUTE MAXIMUM RATINGS

TA = 25°C, unless otherwise noted.

Table 3.

Parameter Rating

VDD to AGND −0.3 V to +7 V

VDD to DGND −0.3 V to +7 V

Analog Input Voltage to AGND

AIN1 to AIN4 −0.3 V to VDD + 0.3 V

Reference Input Voltage to AGND1 −0.3 V to VDD + 0.3 V

Digital Input Voltage to DGND −0.3 V to VDD + 0.3 V

Digital Output Voltage to DGND −0.3 V to VDD + 0.3 V

Operating Temperature Range

A Version −40°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

θJA Thermal Impedance 120°C/W

Lead Temperature, Soldering 260°C

Vapor Phase (60 sec) 215°C

Infrared (15 sec) 220°C

16-Lead SOIC Package, Power Dissipation 450 mW

θJA Thermal Impedance 100°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) 215°C

Infrared (15 sec) 220°C

8-Lead SOIC Package, Power Dissipation 450 mW

θJA Thermal Impedance 157°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) 215°C

Infrared (15 sec) 220°C

MSOP Package, Power Dissipation 450 mW

θJA Thermal Impedance 206°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) 215°C

Infrared (15 sec) 220°C

1 If the reference input voltage is likely to exceed VDD by more than 0.3 V (for

example, 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 the VDD pin. Figure 5 shows how the diode should be connected.

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.

REFIN

BAT81

AD7417

01126-025

Figure 5. Diode Connection

ESD CAUTION

AD7416/AD7417/AD7418

Rev. I | Page 8 of 24

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

NC 1

SDA 2

SCL 3

OTI 4

NC16

CONVST15

VDD

REFIN 5A112

GND 6A211

AIN1 7AIN4

AIN2 8AIN3

NC = NO CONNECT

AD7417

TOP VIEW

(Not to Scale)

01126-005

Figure 6. AD7417 Pin Configuration (SOIC/TSSOP)

Table 4. AD7417 Pin Function Descriptions

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 pin is a logic output. The overtemperature indicator (OTI) is set if the result of a conversion on Channel 0

(temperature sensor) is greater than an 8-bit word in the TOTI setpoint register. The signal is reset at the end of a

serial read operation. Open-drain output.

5 REFIN Reference Input. An external 2.5 V reference can be connected to the AD7417 at this pin. To enable the on-chip

reference, the REFIN pin should be tied to GND. If an external reference is connected to the AD7417, the internal

reference shuts down.

6 GND Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry.

7 to 10 AIN1 to AIN4 Analog Input Channels. The AD7417 has four analog input channels. The input channels are single-ended with

respect to GND. The input channels can convert voltage signals in the range of 0 V to VREF. A channel is selected by

writing to the configuration register of the AD7417.

11 A2 Digital Input. This is the highest programmable bit of the serial bus address.

12 A1 Digital Input. This is the middle programmable bit of the serial bus address.

13 A0 Digital Input. This is the lowest programmable bit of the serial bus address.

14 VDD Positive Supply Voltage, 2.7 V to 5.5 V.

15 CONVST Logic Input Signal. Convert start signal. The rising edge of this signal fully powers up the part. The power-up time

for the part is 4 s. If the CONVST pulse is greater than 4 s, the falling edge of CONVST places the track-and-hold

mode into hold mode and initiates a conversion. If the pulse is less than 4 s, an internal timer ensures that the

track-and-hold does not go into hold, and conversion is not initiated until the power-up time has elapsed. The

track-and-hold goes into track mode again at the end of conversion (see the section). Operating Modes

AD7416/AD7417/AD7418

Rev. I | Page 9 of 24

SDA

SCL

OTI

GND

AD7416

TOP VIEW

(Not to Scale)

1126-006

SDA

SCL

OTI

GND

CONVST

REF

AD7418

TOP VIEW

(Not to Scale)

01126-007

Figure 7. AD7416 Pin Configuration (SOIC/MSOP) Figure 8. AD7418 Pin Configuration (SOIC/MSOP)

Table 5. AD7416 Pin Function Descriptions

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 pin is a logic output. The OTI is set if the result of a conversion on Channel 0 (temperature sensor) is greater

than an 8-bit word in the TOTI setpoint register. The signal is reset at the end of a serial read operation. Open-drain

output.

4 GND Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry.

5 A2 Digital Input. This is the highest programmable bit of the serial bus address.

6 A1 Digital Input. This is the middle programmable bit of the serial bus address.

7 A0 Digital Input. This is the lowest programmable bit of the serial bus address.

8 VDD Positive Supply Voltage, 2.7 V to 5.5 V.

Table 6. AD7418 Pin Function Descriptions

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 OTI is set if the result of a conversion on Channel 0 (temperature sensor) is greater than

an 8-bit word in the TOTI setpoint register. The signal is reset at the end of a serial read operation. Open-drain

output.

4 GND Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry.

5 AIN Analog Input Channel. The input channel is single-ended with respect to GND. The input channel can convert

voltage signals in the range of 0 V to VREF. The analog input channel is selected by writing to the configuration

6 REFIN Reference Input. An external 2.5 V reference can be connected to the AD7418 at this pin. To enable the on-chip

reference, the REFIN pin should be tied to GND. If an external reference is connected to the AD7418, the internal

reference shuts down.

7 VDD Positive Supply Voltage, 2.7 V to 5.5 V.

8 CONVST Logic Input Signal. Convert start signal. The rising edge of this signal fully powers up the part. The power-up time

for the part is 4 s. If the CONVST pulse is greater than 4 s, the falling edge of CONVST places the track-and-hold

mode into hold mode and initiates a conversion. If the pulse is less than 4 s, an internal timer ensures that the

track-and-hold does not go into hold, and conversion is not initiated until the power-up time has elapsed. The

track-and-hold goes into track mode again at the end of conversion (see the section). Operating Modes

AD7416/AD7417/AD7418

Rev. I | Page 10 of 24

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, that is, 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, that is, 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-and-Hold Acquisition Time

Track-and-hold acquisition time is the time required for the

output of the track-and-hold amplifier to reach its final value,

within ±½ LSB, after the end of conversion (the point at which

the track-and-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 AIN input of the AD7417 or AD7418. It

means that the user must wait for the duration of the track-and-

hold acquisition time after the end of conversion, or after a

channel change or step input change to AIN before starting

another conversion, to ensure that the part operates to

specification.

AD7416/AD7417/AD7418

Rev. I | Page 11 of 24

THEORY OF OPERATION

CIRCUIT INFORMATION

The AD7417 and AD7418 are single-channel and four-channel,

15 μs conversion time, 10-bit ADCs 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 ADC 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

−40°C to +125°C. The parts require a 2.5 V reference that can

be provided from the part’s 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 that no external clock is required except when

reading from and writing to the serial port. The on-chip track-

and-hold goes from track mode 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-and-hold

goes into hold mode 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 tempera-

ture sensor is selected. The track-and-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.

The on-chip reference is not available to the user, but REFIN can

be overdriven by an external reference source (2.5 V only).

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.

TYPICAL CONNECTION DIAGRAM

Figure 9 shows a typical connection diagram for the AD7417.

Using the A0, A1, and A2 pins allows the user to select from up

to eight AD7417 devices on the same serial bus, if desired. An

external 2.5 V reference can be connected at the REFIN pin. If an

external reference is used, a 10 μF capacitor should be connected

between REFIN and GND. SDA and SCL form the 2-wire I2C

compatible interface. For applications where power consump-

tion is of concern, the automatic power-down at the end of a

conversion should be used to improve power performance (see

the Operating Modes section.)

+ +

SUPPLY

2.7V TO 5.5V

2-WIRE

SERIAL

INTERFACE

0.1µF10µF

10µF FOR

EXTERNAL

REFERENCE

OPTIONAL

EXTERNAL

REFERENCE

AD780/

REF192

0V TO 2.5V

INPUT

SDA

SCL

GND

OTI

CONVST

VDD

REFIN

AD7417

AIN1

AIN2

AIN3

AIN4

01126-008

MICROCONTROLLER/

MICROPROCESSOR

Figure 9. Typical AD7417 Connection Diagram

ANALOG INPUTS

Figure 10 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 to prevent these

diodes from becoming 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. Capacitor C2 in Figure 10 is typically about 4 pF and

can primarily be attributed to pin capacitance. Resistor R1 is a

lumped component made up of the on resistance of a multiplexer

and a switch. This resistor is typically about 1 kΩ. Capacitor C1

is the ADC sampling capacitor and has a capacitance of 3 pF.

BALANCE

1kΩ

CONVERT PHASE: SWITCH OPEN

TRACK PHASE: SWITCH CLOSED

4pF

3pF

01126-009

Figure 10. Equivalent Analog Input Circuit

ON-CHIP REFERENCE

The AD7417/AD7418 have an on-chip 1.2 V band gap reference

that is amplified 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 the

REFIN pin to analog ground, which causes SW1 (see Figure 11) to

open and the reference amplifier to power up during a conver-

sion. Therefore, the on-chip reference is not available externally.

AD7416/AD7417/AD7418

Rev. I | Page 12 of 24

An external 2.5 V reference can be connected to the REFIN pin.

This has the effect of shutting down the on-chip reference

circuitry.

REF

SW1

26kΩ2.5V

24kΩ

1.2V

EXTERNAL

REFERENCE

DETECT

BUFFER

1126-010

Figure 11. On-Chip Reference

TEMPERATURE MEASUREMENT

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 a constant current. Unfortu-

nately, this technique requires calibration to null out the effect

of the absolute value of VBE, which varies from device to device.

The technique used in the AD7416/AD7417/AD7418 is to

measure the current change in VBE when the device is operated

at two different currents.

This is given by

()

NqKTVBE n1/ ×=Δ

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.

SENSING

TRANSISTOR

TO ADC

SENSING

TRANSISTOR

OUT+

OUT–

IN × I

01126-011

Figure 12. Temperature Measurement Technique

Figure 12 shows the method the AD7416/AD7417/AD7418 use

to measure the 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 form.

The temperature resolution of the ADC is 0.25°C, which corres-

ponds to 1 LSB of the ADC. The ADC can theoretically measure a

temperature span of 255°C; the guaranteed temperature range is

−40°C to +125°C. The result of the conversion is stored in the

temperature value register (0x00) as a 16-bit word. The 10 MSBs

of this word store the temperature measurement (see Table 9

and Table 10).

The temperature conversion formulas using the 10 MSBs of the

temperature value register are

Positive Temperature = ADC Code/4 (1)

Negative Temperature = (ADC Code − 512)/4 (2)

The MSB is removed from ADC Code in Equation 2.

INTERNAL REGISTER STRUCTURE

The AD7417/AD7418 have seven internal registers, as shown in

Figure 13. 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

(READ-ONLY

ADDRESS 0x00)

CONFIGURATION

(READ/WRITE

ADDRESS 0x01)

THYST SETPOINT

(READ/WRITE

ADDRESS 0x02)

TOTI SETPOINT

(READ/WRITE

ADDRESS 0x03)

ADC VALUE

(READ-ONLY

ADDRESS 0x04)

CONFIG2

(READ/WRITE

ADDRESS 0x05)

SDA

DATA

SCL

ADDRESS POINTER

(SELCTS DATA REGISTER

FOR READ/WRITE)

ADDRESS

SERIAL BUS INTERFACE

01126-012

Figure 13. AD7417/AD7418 Register Structure

Address Pointer Register

The address pointer register is an 8-bit register that 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

three LSBs of the address pointer register are used to select a

data register.

Table 7. Address Pointer Register

P71 P61 P51 P41 P31 P2 P1 P0

0 0 0 0 0 Register select

1 P3 to P7 must be set to 0.

AD7416/AD7417/AD7418

Rev. I | Page 13 of 24

Table 8. Register Addresses

P2 P1 P0 Registers

0 0 0 Temperature value

0 0 1 Configuration register

0 1 0 THYST setpoint

0 1 1 TOTI setpoint

1 0 0 ADC value (AD7417/AD7418 only)

1 0 1 Config2 (AD7417/AD7418 only)

Temperature Value Register (Address 0x00)

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. Bit D5 to Bit D0 are unused.

Table 9. 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 10. 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 10. Temperature Data Format

Temperature Digital Output

−128°C 10 0000 0000

−125°C 10 0000 1100

−100°C 10 0111 0000

−75°C 10 1101 0100

−50°C 11 0011 1000

−25°C 11 1001 1100

−10°C 11 1101 1000

−0.25°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 0x01)

The configuration register is an 8-bit, read/write register that is

used to set the operating modes of the AD7416/AD7417/AD7418.

Bit D7 to Bit D5 control the channel selection as outlined in

Table 12. Bits[D7:D5] should always be set to 000 for the AD7416.

Bit D4 and Bit D3 are used to set the length of the fault queue.

D2 sets the sense of the OTI output. D1 selects the comparator

or interrupt mode of operation, and D0 = 1 selects the shutdown

mode (default: D0 = 0).

Table 11. Configuration Register

D7 D6 D5 D4 D3 D2 D1 D0

Channel

selection

Fault

queue

OTI

polarity

Cmp/Int Shutdown

The AD7416 contains a temperature-only channel; the AD7417

has four analog input channels and a temperature channel; and

the AD7418 has two channels, a temperature channel, and an

analog input channel. The temperature channel address for all

parts is the same, Channel 0. The address for the analog input

channel on the AD7418 is Channel 4. Table 12 outlines the

channel selection on the parts, and Tabl e 13 shows the fault

queue settings. D1 and D2 are explained in the OTI Output

section.

Table 12. Channel Selection

D7 D6 D5 Channel Selection

0 0 0 Temperature sensor (all parts), Channel 0

0 0 1 AIN1 (AD7417 only), Channel 1

0 1 0 AIN2 (AD7417 only), Channel 2

0 1 1 AIN3 (AD7417 only), Channel 3

1 0 0 AIN4 (AD7417) and AIN (AD7418), Channel 4

Table 13. Fault Queue Settings

D4 D3 Number of Faults

0 0 1 (power-up default)

0 1 2

1 0 4

1 1 6

THYST Setpoint Register (Address 0x02)

The THYST setpoint register is a 16-bit, read/write register whose

nine MSBs store the THYST setpoint in twos complement format

equivalent to the nine MSBs of the temperature value register.

Bit D6 to Bit D0 are unused.

TOTI Setpoint Register (Address 0x03)

The TOTI setpoint register is a 16-bit, read/write register whose

nine MSBs store the TOTI setpoint in twos complement format

equivalent to the nine MSBs of the temperature value register.

Bit 6 to Bit 0 are unused.

Table 14. THYST Setpoint and TOTI Setpoint Registers

D15 D14 D13 D12 D11 D10 D9 D8 D7

MSB B7 B6 B5 B4 B3 B2 B1 LSB

ADC Value Register (Address 0x04)

The ADC value register is a 16-bit, read-only register whose

10 MSBs store the value produced by the ADC in binary format.

Bit D5 to Bit D0 are unused. Table 15 shows the ADC value

Table 15. ADC Value Register

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6

MSB B8 B7 B6 B5 B4 B3 B2 B1 LSB

ADC Transfer Function

The designed code transitions occur at successive integer

LSB values (that is, 1 LSB, 2 LSB, and so on). The LSB size =

VREF/1024. The ideal transfer function characteristic for the

AD7417 and AD7418 ADC is shown in Figure 14.

AD7416/AD7417/AD7418

Rev. I | Page 14 of 24

ANALOG INPUT

ADC CODE

0V 1/2LSB

111...111

111...110

111...000

011...111

000...010

000...001

000...000

+VREF – 1LSB

1LSB – VREF/1024

01126-013

Figure 14. Ideal Transfer Function Characteristic for the AD7417/AD7418

Config2 Register (Address 0x05)

A second configuration register is included in the AD7417/

AD7418 for the functionality of the CONVST pin. It is an 8-bit

whether the AD7417/AD7418 should be operated in its default

mode (D7 = 0), performing conversions every 355 μs or in its

CONVST pin mode (D7 = 1), where conversions start only

when the CONVST pin is used. Bit 6 contains the Test 1 bit.

When this bit is 0, the I2C filters are enabled (default). Setting

this bit to 1 disables the filters.

Table 16. Config2 Register

D7 D6 D5 D4 D3 D2 D1 D0

Conversion mode Test 1 0 0 0 0 0 0

SERIAL BUS INTERFACE

Control of the AD7416/AD7417/AD7418 is carried out via the

I2C compatible serial bus. The AD7416/AD7417/AD7418 are

connected to this bus as a slave device, under the control of a

master device, for example, 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 set to 0101, and the

three LSBs can be set by the user by connecting the A2 to A0

pins to either VDD or GND. By giving them different addresses,

up to eight AD7416/AD7417 devices 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 set to 0101, and the three LSBs are all set to 0.

If a serial communication occurs during a conversion operation,

the conversion stops and restarts after the communication.

The serial bus protocol operates as follows:

1. The master initiates data transfer by establishing a start condi-

tion, 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 7-bit

address (MSB first) plus an R/W bit, which determines the

direction of the data transfer, that is, 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 acknowl-

edge 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 writes to the

slave device. If the R/W bit is a 1, then the master reads

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, because a low-to-high transi-

tion 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 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 can 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.

Writing to the AD7416/AD7417/AD7418

Depending on the register being written to, there are three

different writes for the AD7416/AD7417/AD7418.

• Writing to the address pointer register for a subsequent read.

To read data from a particular register, the address pointer

not, the correct address must be written to the address pointer

in Figure 15. 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.

• Writing a single byte of data to the configuration register, the

Config2 register, or to the TOTI setpoint or THYST setpoint

registers.

The configuration register is an 8-bit register, so only one

byte of data can be written to it. If only 8-bit temperature

comparisons are required, the temperature LSB can be

ignored in TOTI and THYST, and only eight bits need to be

written to the TOTI setpoint and THYST setpoint registers.

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

AD7416/AD7417/AD7418

Rev. I | Page 15 of 24

written to the selected data register. This is illustrated in

Figure 16.

• Writing two bytes of data to the TOTI setpoint or THYST

setpoint register.

If 9-bit resolution is required for the temperature setpoints,

two bytes of data must be written to the TOTI setpoint and

THYST setpoint registers. This consists of the serial bus

address, the register address written to the address pointer

data register. This is illustrated in Figure 17.

SCL

1 19 9

DA 1001

START BY

MASTER

ACK. BY

AD741x

ACK. BY

AD741x

STOP

MASTER

FRAME 2

ADDRESS POINTER REGISTER BYTE

FRAME 1

SERIAL BUS ADDRESS BYTE

AD741x = AD7416/AD7417/AD7418.

A2 A1 P7 P6 P5 P4 P3 P2 P1 P0A0 R/W

01126-014

Figure 15. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation

SCL

1 1

SDA 1 0 0 1

START BY

MASTER

ACK. BY

AD741x

ACK. BY

AD741x

ACK. BY

AD741x

STOP

MASTER

FRAME 2

ADDRESS POINTER REGISTER BYTE

FRAME 3

DATA BYTE

FRAME 1

SERIAL BUS ADDRESS BYTE

SCL (CONTINUED)

SDA (CONTINUED)

A2 A1 P7 P6 P5 P4 P3 P2 P1 P0

D6D7 D5 D4 D3 D2 D1 D0

A0 R/W

01126-015

AD741x = AD7416/AD7417/AD7418.

Figure 16. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register

SCL

(CONTINUED)

SDA

(CONTINUED)

119

SDA 1 0 0 1

START BY

MASTER

ACK. BY

AD741x

ACK. BY

AD741x

ACK. BY

AD741x

STOP BY

MASTER

ACK. BY

AD741x

STOP

MASTER

FRAME 2

ADDRESS POINTER REGISTER BYTE

FRAME 1

SERIAL BUS ADDRESS BYTE

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

A1 P7 P6 P5 P4 P3 P2 P1 P0A0 R/W

FRAME 3

MOST SIGNIFICANT DATA BYTE

FRAME 4

LEAST SIGNIFICANT DATA BYTE

01126-016

AD741x = AD7416/AD7417/AD7418.

Figure 17. Writing to the Address Pointer Register Followed by Two Bytes of Data to the TOTI Setpoint or THYST Setpoint Register

AD7416/AD7417/AD7418

Rev. I | Page 16 of 24

Reading Data From the AD7416/AD7417/AD7418

Reading data from the AD7416/AD7417/AD7418 is a single-

byte or 2-byte operation. Reading back the contents of the

configuration register is a single-byte read operation, as shown

in Figure 18, with the register address previously having been

set by a single-byte write operation to the address pointer

Reading data from the temperature value register, the TOTI

setpoint or THYST setpoint register is a 2-byte operation, as

shown in Figure 19. It is also possible to read the most

significant bit of a 9-bit or 10-bit register in this manner.

Note that when reading back from the AD7416/AD7417/

AD7418, no more than three bytes of data must be read back.

A stop command must be inserted at the end of the read

communication. If a stop command is not inserted by the

master and the AD7416/AD7417/AD7418 receive more SCL

cycles than the maximum needed for three bytes of data, then

the I2C interface on the AD7416/AD7417/AD7418 pulls the

SDA line low and prevents it from going high again. To recover

the AD7416/AD7417/AD7418 interface, the part must be

powered off and on again. Reference the AN-686 Application

Note, Implementing an I2C® Reset at www.analog.com for more

information on I2C interfaces.

SCL

1 19 9

DA 1 0 0 1

START BY

MASTER

ACK. BY

AD741x1

NO ACK. BY

MASTER

STOP

MASTER

FRAME 2

SINGLE DATA BYTE FROM AD741x1

FRAME 1

SERIAL BUS ADDRESS BYTE

A1 D7 D6 D5 D4 D3 D2 D1 D0A0A2 R/W

01126-017

1AD741x = AD7416/AD7417/AD7418.

Figure 18. Reading a Single Byte of Data from the Configuration Register

SCL

1 1

DA 1001

START BY

MASTER

ACK. BY

AD741x

ACK. BY

MASTER

NO ACK. BY

MASTER

STOP

MASTER

FRAME 2

MOST SIGNIFICANT BYTE FROM AD741x

FRAME 3

LEAST SIGNIFICANT DATA BYTE FROM AD741x

FRAME 1

SERIAL BUS ADDRESS BYTE

SCL (CONTINUED)

SDA (CONTINUED)

A2 A1 D15 D14 D13 D12 D11 D10 D9 D8

D6D7 D5 D4 D3 D2 D1 D0

A0 R/W

01126-018

AD741x = AD7416/AD7417/AD7418.

Figure 19. Reading Two Bytes of Data from the TOTI Setpoint or THYST Setpoint Register

AD7416/AD7417/AD7418

Rev. I | Page 17 of 24

OTI OUTPUT

The OTI output has two operating modes that are selected by

Bit D1 of the configuration register. In the comparator mode,

(D1 = 0), the OTI output becomes active when the temperature

exceeds TOTI and remains active until the temperature falls

below THYST. This mode allows the AD7416/AD7417/AD7418 to

be used as a thermostat, for example, to control the operation of

a cooling fan.

OTI

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 REMAINSACTIVE INDEFINITELY,

ONCE TRIGGERED.

READ

01126-019

Figure 20. Operation of OTI Output (Shown Active Low)

The open-drain configuration of OTI allows the OTI outputs of

several AD7416/AD7417/AD7418 devices to be wire-AND’ed

together when in active low mode.

The OTI output is used to indicate that an out-of-limit tempera-

ture 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 TOTI and remains active even if

the temperature falls below THYST, until it is reset by a read opera-

tion. Once OTI becomes active by the temperature exceeding

TOTI, and resets, it remains inactive even if the temperature

remains, or subsequently rises again, above TOTI. It does not

become active again until the temperature falls below THYST. It

then remains active until reset by a read operation. Once OTI

becomes active by the temperature falling below THYST and then

resets, it remains inactive even if the temperature remains, or

subsequently falls again, below THYST.

OTI is also reset when the AD7416/AD7417/AD7418 are placed

in shutdown mode by setting Bit D0 of the configuration

The OTI output requires an external pull-up resistor. This can

be connected to a voltage different from VDD (for example, to

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 the pull-up resistor that meets

the output high current specification of the OTI output is 30 kΩ,

but higher values can be used if a lower output current is

required. For most applications, a value of 10 kΩ is suitable.

FAULT QUEUE

To avoid false triggering of the AD7416/AD7417/AD7418 in

noisy environments, a fault queue counter is provided that can

be programmed by Bit D3 and Bit D4 of the configuration

OTI becomes active. 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 TOTI

(or less than THYST) must occur. Any reading that breaks the

sequence resets the fault queue counter, so if there are three

readings greater than TOTI followed by a reading less than TOTI,

the fault queue counter is reset without triggering OTI.

POWER-ON DEFAULTS

The AD7416/AD7417/AD7418 always power up with the

following defaults:

• Address pointer pointing to temperature value register

comparator mode

• TOTI = 80°C

• THYST = 75°C

• OTI active low

• Fault queue = 1

These default settings allow the AD7416/AD7417/AD7418 to

be used as a standalone thermostat without any connection to a

serial bus.

OPERATING MODES

The AD7416/AD7417/AD7418 have two possible modes of

operation depending on the value of D0 in the configuration

Mode 1

Normal operation of the AD7416/AD7417/AD7418 occurs

when D0 = 0. In this active mode, a conversion takes place

every 400 μs. After the conversion has taken place, the part

partially powers down, consuming typically 350 μA of the

current until the next conversion occurs.

Two situations can arise in this mode on the request of a tempera-

ture 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 com-

pleted conversion. The next conversion typically occurs 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 VDD = 3 V for each 400 μs cycle, the AD7416/AD7417/

AD7418 spend 40 μs (or 10% of the time) in conversion mode.

The part 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

AD7416/AD7417/AD7418

Rev. I | Page 18 of 24

CONVST Pin Mode

Mode 2

Conversions are initiated only by using the CONVST pin. In

this method of operation, CONVST is normally low.

For applications where temperature measurements are required

at a slower rate, for example, 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 full power-

down because the I2C bus is continuously active.

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-and-hold also enters its hold mode at this time.

If the CONVST high time is less than 4 μs, an internal timer,

initiated by the rising edge of CONVST, holds off the track-

and-hold and the initiation of conversion until the timer times

out (4 μs after the rising edge of CONVST, which corresponds

with the power-up time). The 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 the

conversion starts.

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 power-down,

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.

The CONVST pin should not be pulsed when reading from or

writing to the port.

Figure 21 shows the recommended minimum times for the

CONVST pulse when the temperature channel is selected.

shows the minimum times an analog input channel is

selected.

Figure 22

Thus, the average power dissipation is

3 mW × 0.004 + 60 nW × 0.9996 = 1.2 μW

CONVST

100ns

40µs

01126-023

The fastest throughput rate at which the AD7416/AD7417/

AD7418 can be operated is 2.5 kHz (that is, a read every 400 μs

conversion period). Because TOTI and THYST are 2-byte reads, the

read time with the I2C operating at 100 kbps would be 270 μs. If

temperature reads are called too often, reads will overlap with

conversions, aborting them continuously, which results in

invalid readings.

Figure 21. CONVST When Temperature Channel Selected

CONVST START MODE

CONVST

100ns

15µs

01126-024

The AD7417/AD7418 have an extra mode, set by writing to the

MSB of the Config2 register.

Figure 22. CONVST When VIN Channel Selected

AD7416/AD7417/AD7418

Rev. I | Page 19 of 24

APPLICATIONS INFORMATION

SUPPLY DECOUPLING

The AD7416/AD7417/AD7418 should be decoupled with a

0.1 μF ceramic capacitor between VDD and GND. This is

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 VDD pin is at 0 V. Refer to the AN-588 Application

Note, AD7416/AD7417/AD7418 Power-On Reset Circuit at

www.analog.com for more information. A failed power-on reset

can prevent the default values from being loaded into the AD7416/

AD7417/AD7418 registers. If the correct values are not loaded

into the registers, then the device cannot start operating. The

output from the temperature value and ADC value registers will

be a constant value.

To restart the device operation, the registers have to be loaded

with their default values via the I2C bus. Therefore, in the event

of an inadequate power-on reset and for all three devices, the

following registers should be loaded with their default values:

• Configuration register—default value = 0x00

• Config2 register—default value = 0x00

• THYST setpoint register—default value = 0x4B00

• TOTI setpoint register—default value = 0x5500

MOUNTING THE AD7416/AD7417/AD7418

The AD7416/AD7417/AD7418 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 0.2°C of the surface temperature, due to the low

power consumption of the device. Take care 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 GND 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. Take care to ensure that this is in close 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 that provide a safe environment for the device.

FAN CONTROLLER

Figure 23 shows a simple fan controller that switches on a

cooling fan when the temperature exceeds 80°C and switches it

off again when the temperature falls below 75°C. The AD7416

can be used as a standalone device 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 can be con-

nected directly to the gate of Q2, with R2 as the pull-up resistor.

VDD

3V TO 5.5V

AD7416

10kΩ

2N3904

OR SIMILAR

LOGIC LEVEL

MOSFET RATED

TO SUIT FAN

CURRENT

01126-020

Figure 23. AD7416 Used as a Fan Controller

THERMOSTAT

Figure 24 shows the AD7416 used as a thermostat. The heater

switches on when the temperature falls below THYST and

switches off again when the temperature rises above TOTI. For

this application and for comparator mode, program the OTI

output active low.

3V TO 5.5V

AD7416

10kΩRELAY

2N3904

OR SIMILAR

1N4001

HEATER

SUPLY

RLA1

HEATER

01126-021

Figure 24. AD7416 Used as a Thermostat

AD7416/AD7417/AD7418

Rev. I | Page 20 of 24

SYSTEM WITH MULTIPLE AD7416 DEVICES

The three LSBs of the AD7416 serial address can be set by the

user, allowing eight different addresses from 1001000 to

1001111. Figure 25 shows a system in which eight AD7416

devices are connected to a single serial bus, with their OTI

outputs wire-AND’ed together to form a common interrupt

line. This arrangement means 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.

5.5V

10kΩ

AD7416

SUPER I/O CHIP

PROCESSOR

1126-022

Figure 25. Multiple Connection of AD7416 Devices to a Single Serial Bus

AD7416/AD7417/AD7418

Rev. I | Page 21 of 24

OUTLINE DIMENSIONS

CONTROL LI NG DIM E NSIO NS ARE IN MI LL IMET ERS; INCH DIMENSIONS

(I N PARENTHESE S ) ARE ROUNDED-O FF MILLIMETER EQUIVALENT S FOR

REFE RE NCE ONLYAND ARE NO T APPRO PRI ATE FOR USE IN DESIGN.

COM PLI ANT TO JEDEC S TANDARDS MS-012-AC

10.00 (0.3937)

9.80 ( 0.3858)

16 9

6.20 ( 0 .2441)

5.80 ( 0 .2283)

4.00 ( 0.1575)

3.80 ( 0.1496)

1.27 ( 0.0500)

BSC

SEATING

PLANE

0.25 ( 0.0098)

0.10 ( 0.0039)

0.51 ( 0 .0201)

0.31 ( 0 .0122)

1.75 ( 0.0689)

1.35 ( 0.0531)

0.50 ( 0.0197)

0.25 ( 0.0098)

1.27 ( 0.0500)

0.40 ( 0.0157)

0.25 ( 0.0098)

0.17 ( 0.0067)

COPLANARITY

0.10

8°

0°

060606-A

45°

Figure 26. 16-Lead Standard Small Outline Package [SOIC_N]

Narrow Body

(R-16)

Dimensions shown in millimeters and (inches)

CONT ROLLING DIM E NSIO NS ARE IN MILLIM E TERS; INCH DIM E NSIONS

(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR

REFERENCE ONLY AND ARE NOT APPROPRIATE F OR USE IN DES I GN.

COMP LIANT TO JEDEC S TANDARDS MS-012-AA

012407-A

0.25 ( 0.0098)

0.17 ( 0.0067)

1.27 ( 0.0500)

0.40 ( 0.0157)

0.50 ( 0 .0196)

0.25 ( 0 .0099) 45°

8°

0°

1.75 ( 0 .0688)

1.35 ( 0 .0532)

SEATING

PLANE

0.25 (0.0098)

0.10 (0.0040)

5.00 (0.1968)

4.80 (0.1890)

4.00 ( 0.1574)

3.80 ( 0.1497)

1.27 (0.0500)

BSC

6.20 ( 0.2441)

5.80 ( 0.2284)

0.51 ( 0.0201)

0.31 ( 0.0122)

COPLANARITY

0.10

Figure 27. 8-Lead Standard Small Outline Package [SOIC_N]

Narrow Body

(R-8)

Dimensions shown in millimeters and (inches)

AD7416/AD7417/AD7418

Rev. I | Page 22 of 24

16 9

PIN 1

SEATING

PLANE

8°

0°

4.50

4.40

4.30

6.40

BSC

5.10

5.00

4.90

0.65

BSC

0.15

0.05

1.20

MAX 0.20

0.09 0.75

0.60

0.45

0.30

0.19

COPLANARITY

0.10

COMPLIANT TO JEDEC STANDARDS MO-153-AB

Figure 28. 16-Lead Thin Shrink Small Outline Package [TSSOP]

(RU-16)

Dimensions shown in millimeters

COMP L I ANT T O JEDE C ST ANDARDS M O -187- AA

0.80

0.60

0.40

8°

0°

PIN 1 0.65 BS C

SEATING

PLANE

0.38

0.22

1.10 MA X

3.20

3.00

2.80

COPLANARITY

0.10

0.23

0.08

3.20

3.00

2.80

5.15

4.90

4.65

0.15

0.00

.95

.85

.75

Figure 29. 8-Lead Mini Small Outline Package [MSOP]

(RM-8)

Dimensions shown in millimeters

AD7416/AD7417/AD7418

Rev. I | Page 23 of 24

ORDERING GUIDE

Model1

Temperature

Range

Temperature

Error Package Description Branding

Package

Option

AD7416AR −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7416AR-REEL −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7416AR-REEL7 −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7416ARZ −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7416ARZ-REEL −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7416ARZ-REEL7 −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7416ARM −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C6A RM-8

AD7416ARM-REEL −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C6A RM-8

AD7416ARM-REEL7 −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C6A RM-8

AD7416ARMZ −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C6A# RM-8

AD7416ARMZ-REEL −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C6A# RM-8

AD7416ARMZ-REEL7 −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C6A# RM-8

AD7417-WAFER Bare Die Wafer

AD7417AR −40°C to +125°C ±2°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417AR-REEL −40°C to +125°C ±2°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417AR-REEL7 −40°C to +125°C ±2°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417ARZ −40°C to +125°C ±2°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417ARZ-REEL −40°C to +125°C ±2°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417ARZ-REEL7 −40°C to +125°C ±2°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417ARU −40°C to +125°C ±2°C 16-Lead Thin Shrink Small Outline Package (TSSOP) RU-16

AD7417ARU-REEL −40°C to +125°C ±2°C 16-Lead Thin Shrink Small Outline Package (TSSOP) RU-16

AD7417ARU-REEL7 −40°C to +125°C ±2°C 16-Lead Thin Shrink Small Outline Package (TSSOP) RU-16

AD7417ARUZ −40°C to +125°C ±2°C 16-Lead Thin Shrink Small Outline Package (TSSOP) RU-16

AD7417ARUZ-REEL −40°C to +125°C ±2°C 16-Lead Thin Shrink Small Outline Package (TSSOP) RU-16

AD7417ARUZ-REEL7 −40°C to +125°C ±2°C 16-Lead Thin Shrink Small Outline Package (TSSOP) RU-16

AD7417BR −40°C to +85°C ±1°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417BR-REEL −40°C to +85°C ±1°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417BR-REEL7 −40°C to +85°C ±1°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417BRZ −40°C to +85°C ±1°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417BRZ-REEL −40°C to +85°C ±1°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7417BRZ-REEL7 −40°C to +85°C ±1°C 16-Lead Standard Small Outline Package (SOIC_N) R-16

AD7418ACHIPS Die

AD7418ARZ −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7418ARZ-REEL −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7418ARZ-REEL7 −40°C to +125°C ±2°C 8-Lead Standard Small Outline Package (SOIC_N) R-8

AD7418ARM −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C7A RM-8

AD7418ARM-REEL −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C7A RM-8

AD7418ARM-REEL7 −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) C7A RM-8

AD7418ARMZ −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) T0G RM-8

AD7418ARMZ-REEL −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) T0G RM-8

AD7418ARMZ-REEL7 −40°C to +125°C ±2°C 8-Lead Mini Small Outline Package (MSOP) T0G RM-8

EVAL-AD7416/7/8EBZ Evaluation Board

1 Z = RoHS Compliant Part.

AD7416/AD7417/AD7418

Rev. I | Page 24 of 24

NOTES

I2C refers to a communications protocol originally developed by Philips Semiconductors (Now NXP Semiconductors).

registered trademarks are the property of their respective owners.

D01126-0-11/10(I)

Mouser Electronics

Authorized Distributor

Click to View Pricing, Inventory, Delivery & Lifecycle Information:

Analog Devices Inc.:

AD7417ARU-REEL AD7417AR AD7417BRZ-REEL7 AD7418ARMZ AD7417ARU AD7417ARUZ AD7416ARZ-

REEL7 AD7416ARMZ-REEL7 AD7417BRZ-REEL AD7417ARU-REEL7 AD7417ARUZ-REEL7 AD7416ARM

AD7416ARM-REEL7 AD7417ARZ-REEL AD7418ARZ AD7417ARUZ-REEL AD7417ARZ AD7416ARMZ-REEL

AD7417BR AD7418ARMZ-REEL7 AD7418ARZ-REEL7 AD7417BR-REEL7 AD7418ARZ-REEL AD7417ARZ-REEL7

AD7416ARZ EVAL-AD7416/7/8EBZ AD7416ARMZ AD7416ARZ-REEL AD7417BRZ AD7418ARM AD7417AR-

REEL