AD AD7417AR 10-bit digital temperature sensor (ad7416) and single/four-channel adc (ad7417/ad7418) Datasheet

10-Bit Digital Temperature Sensor (AD7416) and
Four Single-Channel ADCs (AD7417/AD7418)
AD7416/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: –40ⴗC to +125ⴗC
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 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
FUNCTIONAL BLOCK DIAGRAMS
10-BIT
ANALOG-DIGITAL
CONVERTER
BAND GAP
TEMPERATURE
SENSOR
AD7416
TEMPERATURE
VALUE
REGISTER
SETPOINT
COMPARATOR
TOTI SETPOINT
REGISTER
ADDRESS
POINTER
REGISTER
VDD
THYST SETPOINT
REGISTER
OTI
FAULT
QUEUE
COUNTER
CONFIGURATION
REGISTER
GND
A0
SDA
SERIAL BUS
INTERFACE
A1
SCL
A2
VDD
REFIN
GENERAL DESCRIPTION
The AD7417 and AD7418 are 10-bit, 4-channel and singlechannel 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 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 overtemperature indicator
(OTI) output is provided, which becomes active when a programmed limit is exceeded.
OVERTEMP REG B
CHARGE
DISTRIBUTION
DAC
AIN1
AIN2
AIN3
OTI
A
REF
2.5V
CLOCK
SAMPLING
CAPACITOR
MUX
DATA OUT
CONTROL
LOGIC
SCL
I2C
INTERFACE
SDA
+
AIN4
AD7417
VBALANCE
CONVST
NC NC GND
NC = NO CONNECT
VDD
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)
A0
A1
A2
REFIN
OVERTEMP REG B
A>B
OTI
A
TEMP
SENSOR
AIN1
REF
2.5V
CHARGE
DISTRIBUTION
DAC
DATA OUT
MUX
CLOCK
SAMPLING
CAPACITOR
GND
CONTROL
LOGIC
SCL
I2C
INTERFACE
SDA
+
VBALANCE
REV. G
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. Trademarks and
registered trademarks are the property of their respective owners.
A>B
TEMP
SENSOR
AD7418
CONVST
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
© 2004 Analog Devices, Inc. All rights reserved.
AD7416/AD7417/AD7418
AD7417/AD7418–SPECIFICATIONS
(VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted.)
A Version
B Version1
Unit
10
10
Bits
10
±1
10
±1
Bits
LSB max
Differential Nonlinearity2
±1
±1
LSB max
Gain Error2
±3
± 10
± 0.6
±4
± 0.7
±3
± 10
± 0.6
±4
± 0.7
LSB max
LSB max
LSB max
LSB max
LSB max
VREF
0
±1
10
VREF
0
±1
10
V max
V min
µA max
pF max
±2
±3
1/4
±1
±2
1/4
°C max
°C max
°C/LSB
400
400
ns max
Source Impedance < 10 Ω.
30
15
30
15
µs max
µs max
Typically 27 µs.
Typically 10 µs.
2.625
2.375
40
10
2.625
2.375
40
10
V max
V min
kΩ min
pF max
2.5 V + 5%.
2.5 V – 5%.
ON-CHIP REFERENCE
Reference Error6
Temperature Coefficient6
± 25
80
± 25
80
mV max
ppm/°C typ
DIGITAL INPUTS
Input High Voltage, VIH
Input Low Voltage, VIL
Input Leakage Current
VDD × 0.7
VDD × 0.3
1
VDD × 0.7
VDD × 0.3
1
V min
V max
µA max
DIGITAL OUTPUTS
Output Low Voltage, VOL
Output High Current
0.4
1
0.4
1
V max
µA max
IOL = 3 mA.
VOH = 5 V.
5.5
2.7
5.5
2.7
V max
V min
For Specified Performance.
600
1
600
1
µA max
µA max
6
60
600
3
6
60
600
3
µW typ
µW typ
µW typ
µW max
Parameter
DC ACCURACY
Resolution
Minimum Resolution for Which No
Missing Codes Are Guaranteed
Relative Accuracy2
Gain Error Match2
Offset Error2
Offset Error Match
ANALOG INPUTS
Input Voltage Range
Input Leakage Current3
Input Capacitance
TEMPERATURE SENSOR1
Measurement Error
Ambient Temperature 25°C
TMIN to TMAX
Temperature Resolution
CONVERSION RATE
Track-and-Hold Acquisition Time4
Conversion Time
Temperature Sensor
Channels 1 to 4
REFERENCE INPUT5, 6
REFIN Input Voltage Range6
Input Impedance
Input Capacitance
POWER REQUIREMENTS
VDD
IDD
Normal Operation
Power-Down
Auto Power-Down Mode
10 SPS Throughput Rate
1 kSPS Throughput Rate
10 kSPS Throughput Rate
Power-Down
Test Conditions/Comments
Any Channel.
This Specification Is Typical for VDD of
3.6 V to 5.5 V.
This Specification Is Typical for VDD of
3.6 V to 5.5 V.
External Reference.
Internal Reference.
AD7417 Only.
AD7417 Only.
Nominal 2.5 V.
–2–
Logic Inputs = 0 V or VDD.
50 nA Typically.
VDD = 3 V. See Operating Modes.
Typically 0.15 µW.
REV. G
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 –40°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 Temperature Sensor section.
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
TEMPERATURE SENSOR AND ADC
Accuracy
Resolution
Temperature Conversion Time
Update Rate, tR
OTI Delay
Supply Current
Max
Unit
Test Conditions/Comments
± 2.0
°C
± 3.0
°C
TA = –25°C to +100°C
(VDD = 3 V min)1
TA = –40°C to +125°C
(VDD = 3 V min)1
10
Bits
µs
µs
ms
mA
µA
µA
°C
°C
40
400
1 × tR
350
0.2
80
75
TOTI Default Temperature
THYST Default Temperature
DIGITAL INPUTS
Input High Voltage, VIH
Input Low Voltage, VIL
Input High Current, IIH
Input Low Current, IIL
Input Capacitance, CIN
VDD × 0.7
–0.3
V
V
µA
µA
pF
VIN = 5 V
VIN = 0 V
All Digital Inputs
0.4
1
250
0.8
V
µA
ns
V
IOL = 3 mA
VOH = 5 V
CL = 400 pF, IO = 3 mA
IOUT = 4 mA
2.5
50
0
µs
ns
ns
AD7416/AD7417/AD7418
See Figure 1
See Figure 1
See Figure 1
50
ns
See Figure 1
ns
ns
See Figure 1
See Figure 1
DIGITAL OUTPUTS
Output Low Voltage, VOL
Output High Current
Output Fall Time, tf
OS Output Low Voltage, VOL
50
300
NOTES
1
For VDD = 2.7 V to 3 V, T A 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.
t1
SCL
t4
t2
t5
SDA
DATA IN
t3
SDA
DATA OUT
t6
Figure 1. Diagram for Serial Bus Timing
REV. G
Depends on Fault Queue Setting
I2C Active
I2C Inactive
Shutdown Mode
VDD + 0.5
VDD × 0.3
+1.0
–1.0
+0.005
–0.005
20
AC ELECTRICAL CHARACTERISTICS2
Serial Clock Period, t1
Data In Setup Time to SCL High, t2
Data Out Stable after SCL Low, t3
SDA Low Setup Time to SCL Low
(Start Condition), t4
SDA High Hold Time after SCL High
(Stop Condition), t5
SDA and SCL Fall Time, t6
6 × tR
1.0
600
1.5
–3–
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 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 overtemperature register (OTR).
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 will shut down.
6
GND
Ground reference for track-and-hold, comparator and capacitor DAC, and digital circuitry.
7–10
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 0 V to VREF. A channel is selected by writing to the configuration register of the AD7417. (See Control Byte section.)
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
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 µs. If the CONVST pulse is greater than 4 µs, 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 µs,
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 Operating Mode section.)
AD7417 PIN CONFIGURATION
SOIC/TSSOP
16 NC
NC 1
15 CONVST
SDA 2
14 VDD
SCL 3
OTI 4
AD7417
13 A0
TOP VIEW
REFIN 5 (Not to Scale) 12 A1
11 A2
GND 6
10 AIN4
AIN1 7
AIN2 8
9
AIN3
NC = NO CONNECT
–4–
REV. G
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 OTI is set if the result of a conversion on Channel 0 (temperature sensor) is
greater that an 8-bit word in the OTR. The signal is reset at the end of a serial read operation. Opendrain output.
4
GND
Ground reference for track-and-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.
8
VDD
Positive 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 OTI is set if the result of a conversion on Channel 0 (temperature sensor) is
greater that an 8-bit word in the OTR. The signal is reset at the end of a serial read operation. Opendrain 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 0 V to VREF. The analog input channel is selected by writing to the
configuration register of the AD7418 and choosing Channel 4. (See Control Byte section.)
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 will shut 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 µs. If the CONVST pulse is greater than 4 µs, 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 µs, 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 Operating Mode section.)
AD7416 PIN CONFIGURATION
AD7418 PIN CONFIGURATION
SOIC/MSOP
SOIC/MSOP
SDA 1
SCL 2
AD7416
8
VDD
SDA 1
7
A0
SCL 2
REV. G
5
CONVST
VDD
TOP VIEW
OTI 3 (Not to Scale) 6 REFIN
TOP VIEW
OTI 3 (Not to Scale) 6 A1
GND 4
8
AD7418
GND 4
A2
–5–
7
5
AIN
AD7416/AD7417/AD7418
ABSOLUTE MAXIMUM RATINGS 1
8-Lead SOIC Package, Power Dissipation . . . . . . . . . 450 mW
␪JA 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
␪JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 206°C/W
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . 215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . 220°C
(TA = 25°C, unless otherwise noted.)
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 AGND2 . . –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
␪JA 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
␪JA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 100°C/W
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 V DD 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 REF IN pin and VDD pin. The
diagram below shows how the diode should be connected.
REFIN
VDD
BAT81
AD7417
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. G
AD7416/AD7417/AD7418
ORDERING GUIDE
Model
AD7416ACHIPS
AD7416AR
AD7416AR-REEL
AD7416AR-REEL7
AD7416ARZ*
AD7416ARZ-REEL*
AD7416ARZ-REEL7*
AD7416ARM
AD7416ARM-REEL
AD7416ARM-REEL7
AD7416ARMZ*
AD7416ARMZ-REEL*
AD7416ARMZ-REEL7*
AD7417ACHIPS
AD7417AR
AD7417AR-REEL
AD7417AR-REEL7
AD7417ARU
AD7417ARU-REEL
AD7417ARU-REEL7
AD7417BR
AD7417BR-REEL
AD7417BR-REEL7
AD7418ACHIPS
AD7418AR
AD7418AR-REEL
AD7418AR-REEL7
AD7418ARM
AD7418ARM-REEL
AD7418ARM-REEL7
AD7418ARUZ*
AD7418ARUZ-REEL*
AD7418ARUZ-REEL7*
EVAL-AD7416/AD7417/
AD7418EB
Temperature
Range
Temperature
Error
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 1°C
± 1°C
± 1°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
± 2°C
Package
Description
Die
8-Lead Standard Small Outline Package (SOIC)
8-Lead Standard Small Outline Package (SOIC)
8-Lead Standard Small Outline Package (SOIC)
8-Lead Standard Small Outline Package (SOIC)
8-Lead Standard Small Outline Package (SOIC)
8-Lead Standard Small Outline Package (SOIC)
8-Lead Micro Small Outline Package (MSOP)
8-Lead Micro Small Outline Package (MSOP)
8-Lead Micro Small Outline Package (MSOP)
8-Lead Micro Small Outline Package (MSOP)
8-Lead Micro Small Outline Package (MSOP)
8-Lead Micro Small Outline Package (MSOP)
Die
16-Lead Standard Small Outline Package (SOIC)
16-Lead Standard Small Outline Package (SOIC)
16-Lead Standard Small Outline Package (SOIC)
16-Lead Thin Shrink Small Outline Package (TSSOP)
16-Lead Thin Shrink Small Outline Package (TSSOP)
16-Lead Thin Shrink Small Outline Package (TSSOP)
16-Lead Standard Small Outline Package (SOIC)
16-Lead Standard Small Outline Package (SOIC)
16-Lead Standard Small Outline Package (SOIC)
Die
8-Lead Standard Small Outline Package (SOIC)
8-Lead Standard Small Outline Package (SOIC)
8-Lead Standard Small Outline Package (SOIC)
8-Lead Micro Small Outline Package (MSOP)
8-Lead Micro Small Outline Package (MSOP)
8-Lead Micro Small Outline Package (MSOP)
16-Lead Thin Shrink Small Outline Package (TSSOP)
16-Lead Thin Shrink Small Outline Package (TSSOP)
16-Lead Thin Shrink Small Outline Package (TSSOP)
Evaluation Board
*Pb-Free Part
REV. G
–7–
Branding
Package
Option
C6A
C6A
C6A
C6A
C6A
C6A
RN-8
RN-8
RN-8
RN-8
RN-8
RN-8
RM-8
RM-8
RM-8
RM-8
RM-8
RM-8
RN-16
RN-16
RN-16
RU-16
RU-16
RU-16
RN-16
RN-16
RN-16
C7A
C7A
C7A
RN-8
RN-8
RN-8
RM-8
RM-8
RM-8
RU-16
RU-16
RU-16
AD7416/AD7417/AD7418
(continued from page 1)
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-andhold acquisition time after the end of conversion or after a channel
change/step input change to AIN before starting another conversion, to ensure that the part operates to specification.
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’s 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 MSOP packages.
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.
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 overtemperature 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.
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-and-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-and-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-and-hold acquisition time of the AD7417/AD7418 is 400 ns.
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
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.
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.
The on-chip reference is not available to the user, but REFIN
can be overdriven by an external reference source (2.5 V only).
Gain Error Match
This is the difference in gain error between any two channels.
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.
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 ± 1/2 LSB, after the end of conversion (the point at which
the track-and-hold returns to track mode). It also applies to
–8–
REV. G
AD7416/AD7417/AD7418
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. This causes SW1 (see Figure 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 REFIN pin.
This has the effect of shutting down the on-chip reference circuitry.
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 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 consumption 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 this data sheet.
REFIN
+
EXTERNAL
REFERENCE
DETECT
1.2V
SUPPLY
2.7V TO
5.5V
10␮F
2-WIRE
SERIAL
INTERFACE
0.1␮F
1.2V
+
SW1
26k⍀
VDD
AIN1
AIN2
AIN3
AIN4
0V TO 2.5V
INPUT
OTI
␮C/␮P
Figure 4. On-Chip Reference
A0
A1
A2
GND
TEMPERATURE MEASUREMENT
REFIN
AD780/
REF-192
BUFFER
24k⍀
CONVST
AD7417
OPTIONAL
EXTERNAL
REFERENCE
2.5V
SCL
SDA
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. Unfortunately, this technique requires calibration to null out the effect
of the absolute value of VBE, which varies from device to device.
10␮F FOR
EXTERNAL
REFERENCE
Figure 2. Typical Connection Diagram
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.
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 kΩ. The capacitor C1 is
the ADC sampling capacitor and has a capacitance of 3 pF.
This is given by
∆VBE = KT / q × 1n (N )
where:
K is Boltzmann’s constant.
q is the charge on the electron (1.6 × 10-19 Coulombs).
T is the absolute temperature in Kelvins.
N is the ratio of the two currents.
VDD
I
NⴛI
VDD
D1
R1
1k⍀
VOUTⴙ
C1
3pF
VBALANCE
AIN
C2
4pF
D2
TO ADC
SENSING
TRANSISTOR
CONVERT PHASE – SWITCH OPEN
TRACK PHASE – SWITCH CLOSED
SENSING
TRANSISTOR
Figure 3. Equivalent Analog Input Circuit
ON-CHIP REFERENCE
Figure 5. Temperature Measurement Technique
The AD7416/AD7417/AD7418 has an on-chip 1.2 V band gap
reference that is gained up by a switched capacitor amplifier to
give an output of 2.5 V. The amplifier is only powered up at the
REV. G
–9–
VOUTⴚ
AD7416/AD7417/AD7418
Figure 5 shows the method the AD7416/AD7417/AD7418 uses
to measure the device temperature. To measure ⌬VBE, 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 ⌬VBE.
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
register to which subsequent data bytes are written. Only the
three LSBs of this register are used to select a data register.
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 corresponds 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 (00h) as a 16-bit word. The
10 MSBs of this word store the temperature measurement (see
Table III and Table IV).
The temperature conversion formula using the 10 MSBs of the
Temperature Value Register is
1. Positive Temperature = ADC Code/4
2. Negative Temperature = (ADC Code* – 512)/4
*MSB is removed from the ADC Code.
INTERNAL REGISTER STRUCTURE
The AD7417/AD7418 has seven internal registers, as shown in
Figure 6. 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).
Table I. Address Pointer Register
P7*
P6*
P5*
P4*
P3*
P2
0
0
0
0
0
Register Select
Table II. Register Addresses
P2
P1
P0
Registers
0
0
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
Temperature Value (Read-Only)
Config Register (Read/Write)
THYST (Read/Write)
TOTI
ADC (AD7417/AD7418 Only)
Config2 (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
CONFIGURATION
REGISTER
(READ/WRITE
ADDRESS 01h)
D15 D14
D13
D12
D11 D10
D9
D8
D7
D6
MSB B8
B7
B6
B5
B3
B2
B1
LSB
B4
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.
THYST SETPOINT
REGISTER
(READ/WRITE
ADDRESS 02h)
Table IV. Temperature Data Format
TOTI SETPOINT
REGISTER
(READ/WRITE
ADDRESS 03h)
ADC
REGISTER
(READ-ONLY
ADDRESS 04h)
ADDRESS
P0
*P3 to P7 must be set to 0.
TEMPERATURE
VALUE
REGISTER
(READ-ONLY
ADDRESS 00h)
ADDRESS POINTER
REGISTER
(SELECTS DATA REGISTER
FOR READ/WRITE)
P1
DATA
CONFIG2
REGISTER
(READ/WRITE
ADDRESS 05h)
SERIAL
BUS
INTERFACE
SDA
SCL
Figure 6. AD7417/AD7418 Register Structure
–10–
Temperature
Digital Output
–128°C
–125°C
–100°C
–75°C
–50°C
–25°C
–0.25°C
0°C
+0.25°C
+10°C
+25°C
+50°C
+75°C
+100°C
+125°C
+127°C
10 0000 0000
10 0000 1100
10 0111 0000
10 1101 0100
11 0011 1000
11 1001 1100
11 1111 1111
00 0000 0000
00 0000 0001
00 0010 1000
00 0110 0100
00 1100 1000
01 0010 1100
01 1001 0000
01 1111 0100
01 1111 1100
REV. G
AD7416/AD7417/AD7418
CONFIGURATION REGISTER (ADDRESS 01h)
ADC VALUE REGISTER (ADDRESS 04h)
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
the comparator or interrupt mode of operation, and D0 = 1
selects the shutdown mode (Default D0 = 0).
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. ADC Value Register
D15
D14 D13 D12
D11
D10
D9
D8
D7
D6
MSB
B8
B5
B4
B3
B2
B1
LSB
B7
B6
Table V. Configuration Register
D7
D6
D5
D4
Channel
Selection
D3
Fault
Queue
D2
D1
D0
OTI
Polarity
Cmp/
Int
Shutdown
ADC Transfer Function
The designed code transitions occur at successive integer LSB
values (i.e., 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 7.
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, 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.
ADC CODE
111...111
111...110
111...000
1LSB = V REF/1024
011...111
000...010
000...001
000...000
Table VI. Channel Selection
0V 1/2LSB
+VREF – 1LSB
ANALOG INPUT
D7
D6
D5
Channel Selection
0
0
0
0
1
0
0
1
1
0
0
1
0
1
0
Temperature Sensor (All Parts)
AIN1 (AD7417 Only)
AIN2 (AD7417 Only)
AIN3 (AD7417 Only)
AIN4 (AD7417) and AIN (AD7418)
Table VII. Fault Queue Settings
D4
D3
Number of Faults
0
0
1
1
0
1
0
1
1 (Power-Up Default)
2
4
6
Figure 7. Ideal Transfer Function Characteristic
for the AD7417/AD7418
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 its
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 I2C filters are enabled (default). A 1
disables the filters.
Table X. CONFIG2 Register
THYST SETPOINT REGISTER (ADDRESS 02h)
D7
D6
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. Bits 6 to 0 are unused.
Conversion Mode
Test 1 0
TOTI SETPOINT REGISTER (ADDRESS 03h)
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. 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
REV. G
D5
D4
D3
D2
D1
D0
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 is
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 set to 0101, while 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/AD7417s can be connected to a single serial bus,
–11–
AD7416/AD7417/AD7418
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, while the three LSBs are all set to zero.
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.
If a serial communication occurs during a conversion operation,
the conversion will stop and will restart after the communication.
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.
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 7-bit address (MSB first) plus an 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.
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.
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, then the master will read
from the slave device.
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 8. 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
to the TOTI, THYST registers.
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, since a low-to-high transition
when the clock is high may be interpreted as a stop signal.
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 be
written to the TOTI and THYST registers.
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
1
Writing a single byte of data to one of these registers consists
of the serial bus address, the data register address written to
9
1
9
SCL
0
1
SDA
0
A2
1
A0
A1
P6
P7
R/W
P5
P3
P4
P1
P2
P0
ACK. BY
AD7416
START BY
MASTER
ACK. BY
AD7416
STOP BY
MASTER
FRAME 2
ADDRESS POINTER REGISTER BYTE
FRAME 1
SERIAL BUS ADDRESS BYTE
Figure 8. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation
1
9
9
1
SCL
SDA
1
0
0
1
A2
A1
A0
START BY
MASTER
R/W
P7
P6
P5
P4
P3
P2
P1
P0
ACK. BY
AD7416
ACK. BY
AD7416
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
1
9
SCL (CONTINUED)
SDA (CONTINUED)
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
AD7416
STOP BY
MASTER
FRAME 3
DATA BYTE
Figure 9. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register
–12–
REV. G
AD7416/AD7417/AD7418
the Address Pointer Register, followed by the data byte written to the selected data register. This is illustrated in Figure 9.
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
11, the register address previously having been set by a singlebyte write operation to the Address Pointer Register.
3. Writing two bytes of data to the TOTI or THYST Register.
If 9-bit resolution is required for the temperature setpoints,
two bytes of data must be written to the TOTI and THYST
registers. This consists of the serial bus address, the register
address written to the address pointer register, followed by
two data bytes written to the selected data register. This is
illustrated in Figure 10.
1
Reading data from the temperature value, TOTI or THYST Register, is a two-byte operation, as shown in Figure 12. It is also
possible to read the most significant bit of a 9-bit/10-bit register
in this manner.
9
1
9
SCL
SDA
1
0
0
A2
1
A0
A1
R/W
START BY
MASTER
P7
P6
P5
P4
P3
P2
P1
P0
ACK. BY
AD7416
ACK. BY
AD7416
FRAME 2
ADDRESS POINTER REGISTER BYTE
FRAME 1
SERIAL BUS ADDRESS BYTE
1
9
1
9
SCL
(CONTINUED)
SDA
(CONTINUED)
D15
D14
D13
D12
D11
D9
D10
D7
D8
D6
D5
D4
D3
D2
D1
D0
ACK. BY STOP BY
AD7416 MASTER
ACK. BY
AD7416
FRAME 3
MOST SIGNIFICANT DATA BYTE
STOP BY
MASTER
FRAME 4
LEAST SIGNIFICANT DATA BYTE
Figure 10. Writing to the Address Pointer Register Followed by Two Bytes of Data to the TOTI or THYST Register
1
9
1
9
SCL
SDA
1
0
0
1
A2
A1
A0
D7
R/W
D6
D5
D4
D3
D2
D1
ACK. BY
AD7416
START BY
MASTER
D0
NO ACK. BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
STOP BY
MASTER
FRAME 2
SINGLE DATA BYTE FROM AD7416
Figure 11. Reading a Single Byte of Data from the Configuration Register
1
9
9
1
SCL
SDA
1
0
0
1
A2
A1
A0
D15
R/W
D14
D13
D12
D11
D10
D9
D8
ACK. BY
AD7416
START BY
MASTER
ACK. BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
MOST SIGNIFICANT DATA BYTE FROM AD7416
1
9
SCL (CONTINUED)
SDA (CONTINUED)
D7
D6
D5
D4
D3
D2
D1
D0
NO ACK. BY STOP BY
MASTER
MASTER
FRAME 3
LEAST SIGNIFICANT DATA BYTE FROM AD7416
Figure 12. Reading Two Bytes of Data from the TOTI or THYST Register
REV. G
–13–
AD7416/AD7417/AD7418
Please note that when reading back from the ADT7416/
ADT7417/ADT7418, 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 ADT7416/ADT7417/ADT7418 receives
more SCL cycles than the maximum needed for three bytes of
data, then the I2C interface on the ADT7416/ADT7417/
ADT7418 will pull the SDA line low and prevent it from going
high again. To recover the ADT7416/ADT7417/ADT7418
interface the part must be powered off and on again. Reference
the application note, AN-686, on the Analog Devices website
for more information on I2C interfaces.
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
will meet the output high current specification of the OTI output is 30 kΩ, but higher values may be used if a lower output
current is required. For most applications, a value of 10 kΩ will
prove suitable.
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 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.
TOTI
THYST
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 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 TOTI
(or less than THYST) must occur. Any reading that breaks the
sequence will reset the fault queue counter, so if there are three
readings greater than TOTI followed by a reading less than TOTI,
the fault queue counter will be reset without triggering OTI.
POWER-ON DEFAULTS
The AD7416/AD7417/AD7418 always powers up with the
following defaults.
OTI OUTPUT
COMPARATOR
MODE
Address pointer pointing to Temperature Value Register comparator mode
OTI OUTPUT
INTERRUPT
MODE
TOTI = 80°C
THYST = 75°C
OTI Active LOW
Fault Queue = 1
READ* READ* READ* READ* READ* READ* READ*
*IN INTERRUPT MODE, A READ OPERATION OR SHUTDOWN RESETS THE OTI
OUTPUT; OTHERWISE THE OTI OUTPUT REMAINS ACTIVE INDEFINITELY, ONCE
TRIGGERED.
Figure 13. 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.
These default settings allow the AD7416/AD7417/AD7418 to
be used as a standalone thermostat without any connection to a
serial bus.
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.
OPERATING MODES
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 operation. Once OTI has become active by the temperature exceeding
TOTI, and has then been reset, it will remain inactive even if the
temperature remains, or subsequently rises again, above TOTI. It
will not become active again until the temperature falls below
THYST. It will then remain active until reset by a read operation. Once OTI has become active by the temperature falling
below THYST and then reset, it will remain inactive even if the
temperature remains, or subsequently falls again, below THYST.
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 the current until
the next conversion occurs.
OTI is also reset when the AD7416/AD7417/AD7418 is placed
in shutdown mode by setting Bit D0 of the Configuration Register to 1.
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.
The AD7416/AD7417/AD7418 has two possible modes of
operation depending on the value of D0 in the Configuration
Register.
Mode 1
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.
–14–
REV. G
AD7416/AD7417/AD7418
With a VDD = 3 V, for each 400 µs cycle, the AD7416 spends
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
The CONVST pin should not be pulsed when reading from or
writing to the port.
Figure 17 shows the recommended minimum times for the
CONVST pulse when the temperature channel is selected.
Figure 18 shows the minimum times an analog input channel
is selected.
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 I2C 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 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. Thus, the average power dissipation is
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 application note
AN-588 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 will not start operating. The
output from the value registers will be a constant value.
To get the device operating again, the registers will 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:
3 mW × 0.004 + 60 nW × 0.9996 = 1.2 µW
Configuration Register 1—Default Value = 00h
Configuration Register 2—Default Value = 00h
THYST Setpoint Register—Default Value = 4B00h
TOTI Setpoint Register—Default Value = 5500h
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 TOTI and THYST are 2-byte reads, the
read time with the I2C operating at 100 kbit/s would be 270 µs.
If temperature reads are called too often, reads will overlap
with conversions, aborting them continuously, which results in
invalid readings.
MOUNTING THE AD7416
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
will be within about 0.2°C of the surface temperature, thanks to
the device’s low power consumption. Care should be taken to
insulate the back and leads of the device from the air, if the
ambient air temperature is different from the surface temperature being measured.
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-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-andhold 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). 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.
REV. G
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 that provide a safe environment for
the device.
–15–
AD7416/AD7417/AD7418
FAN CONTROLLER
THERMOSTAT
Figure 14 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 standalone 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 connected
directly to the gate of Q2 with R2 as the pull-up resistor.
Figure 15 shows the AD7416 used as a thermostat. The heater
will be switched ON when the temperature falls below THYST
and switched OFF again when the temperature rises above
TOTI. For this application and for comparator mode, the OTI
output should be programmed active low.
VDD
3V TO
5.5V
HEATER
12V
R1
10k⍀
RELAY
D1
1N4001
VDD
3V TO 5.5V
Q1
2N3904
OR SIMILAR
AD7416
R1
10k⍀
Q2
LOGIC LEVEL
MOSFET RATED
TO SUIT FAN
CURRENT
R2
10k⍀
Q1
2N3904
OR SIMILAR
AD7416
RLA1
HEATER
SUPPLY
Figure 15. AD7416 Used as a Thermostat
SYSTEM WITH MULTIPLE AD7416S
Figure 14. AD7416 Used as a Fan Controller
The three LSBs of the AD7416’s serial address can be set by the
user, allowing eight different addresses from 1001000 to 1001111.
Figure 16 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.
AD7416
AD7416
AD7416
AD7416
AD7416
AD7416
AD7416
AD7416
R1
10k⍀
PROCESSOR
SUPER I/O CHIP
VDD
3V TO 5.5V
Figure 16. Multiple Connection of AD7416s to a Single Serial Bus
100ns
100ns
CONVST
CONVST
40␮s
15␮s
Figure 17. CONVST When Temperature Channel Selected
Figure 18. CONVST When VIN Channel(s) Selected
–16–
REV. G
AD7416/AD7417/AD7418
OUTLINE DIMENSIONS
16-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-16)
8-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
Dimensions shown in millimeters and (inches)
5.00 (0.1968)
4.80 (0.1890)
10.00 (0.3937)
9.80 (0.3858)
4.00 (0.1575)
3.80 (0.1496)
16
9
1
8
6.20 (0.2441)
5.80 (0.2283)
4.00 (0.1574)
3.80 (0.1497)
1.75 (0.0689)
1.35 (0.0531)
1.27 (0.0500)
BSC
0.50 (0.0197)
ⴛ 45ⴗ
0.25 (0.0098)
0.25 (0.0098)
0.10 (0.0039)
5
1
4
6.20 (0.2440)
5.80 (0.2284)
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
8ⴗ
0.51 (0.0201) SEATING
0.25 (0.0098) 0ⴗ 1.27 (0.0500)
PLANE
0.31 (0.0122)
0.40 (0.0157)
0.17 (0.0067)
COPLANARITY
0.10
8
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
SEATING
0.10
PLANE
COMPLIANT TO JEDEC STANDARDS MS-012AC
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
0.50 (0.0196)
ⴛ 45ⴗ
0.25 (0.0099)
1.75 (0.0688)
1.35 (0.0532)
8ⴗ
0.25 (0.0098) 0ⴗ 1.27 (0.0500)
0.40 (0.0157)
0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
16-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-16)
8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
Dimensions shown in millimeters
3.00
BSC
5.10
5.00
4.90
8
16
4.50
4.40
4.30
5
4.90
BSC
3.00
BSC
9
1
6.40
BSC
4
PIN 1
1
0.65 BSC
8
PIN 1
0.20
0.09
0.65
BSC
0.30
0.19
COPLANARITY
0.10
1.10 MAX
0.15
0.00
1.20
MAX
0.15
0.05
SEATING
PLANE
8ⴗ
0ⴗ
0.38
0.22
COPLANARITY
0.10
0.75
0.60
0.45
0.23
0.08
8ⴗ
0ⴗ
0.80
0.60
0.40
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MO-187AA
COMPLIANT TO JEDEC STANDARDS MO-153AB
Purchase of licensed I 2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I 2C
Patent Rights to use these components in an I 2C system, provided that the system conforms to the I 2C Standard Specification as defined by Philips.
REV. G
–17–
AD7416/AD7417/AD7418
Revision History
Location
Page
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
–18–
REV. G
–19–
–20–
C01126–0–8/04(G)