AD7416/17/18 Data Sheet
REV. D
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
a
AD7416/AD7417/AD7418
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 2002
10-Bit Digital Temperature Sensor (AD7416) and
Four/Single-Channel ADCs (AD7417/AD7418)
FUNCTIONAL BLOCK DIAGRAMS
+V
S
OTI
GND
SDA
SCL
FAULT
QUEUE
COUNTER
SETPOINT
COMPARATOR
T
OTI
SETPOINT
REGISTER
T
HYST
SETPOINT
REGISTER
TEMPERATURE
VALUE
REGISTER
A0
A1
A2
CONFIGURATION
REGISTER
SERIAL BUS
INTERFACE
BANDGAP
TEMPERATURE
SENSOR
10-BIT
ANALOG-DIGITAL
CONVERTER
ADDRESS
POINTER
REGISTER
AD7416
CONTROL
LOGIC
A > B
REF
IN
V
DD
OTI
SCL
SDA
A2
A1
A0
CONVST
V
IN1
V
IN2
V
IN3
V
IN4
+
TEMP
SENSOR
SAMPLING
CAPACITOR
V
BALANCE
CLOCK
A
B
REF
2.5V
CHARGE
DISTRIBUTION
DAC
I
2
C
INTERFACE
MUX
OVER-TEMP REG
NC
NC GND
DATA OUT
NC = NO CONNECT
AD7417
CONTROL
LOGIC
A > B
V
DD
OTI
SCL
SDA
V
IN1
+
SAMPLING
CAPACITOR
V
BALANCE
CLOCK
A
B
I
2
C
INTERFACE
MUX
OVER-TEMP REG
AGND
DATA OUT
TEMP
SENSOR
REF
IN
CONVST
REF
2.5V
CHARGE
DISTRIBUTION
DAC
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: 55 C to +125 C
On-Chip Track/Hold
Over-Temperature Indicator
Automatic Power Down at the End of a Conversion
Wide Operating Supply Range: 2.7 V to 5.5 V
I
2
C
-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
GENERAL DESCRIPTION
The AD7417 and AD7418 are 10-bit, 4- and single-channel
A/D converters with an on-chip temperature sensor that can
operate from a single 2.7 V to 5.5 V power supply. The devices
contain a 15
s successive-approximation converter, a 5-channel
multiplexer, a temperature sensor, a clock oscillator, a track/
hold, and a reference (2.5 V). The AD7416 is a temperature-
monitoring-only device in an 8-lead package.
The temperature sensor on the parts can be accessed via multi-
plexer 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 (
1C @ 25C).
On-chip registers can be programmed with high and low tem-
perature limits, and an open drain Over-Temperature Indicator
(OTI) output is provided, which becomes active when a pro-
grammed limit is exceeded.
A configuration register allows programming of the sense of the
OTI output (active high or active low) and its operating mode
(comparator or interrupt). A programmable fault queue counter
allows the number of out of limit measurements that must occur
before triggering the OTI output to be set, to prevent spurious
triggering of the OTI output in noisy environments.
(continued on page 7)
I
2
C is a registered trademark of Philips Corporation.
REV. D
2
AD7416/AD7417/AD7418
AD7417/AD7418SPECIFICATIONS
(V
DD
= 2.7 V to 5.5 V, GND = 0 V, REF
IN
= 2.5 V, unless otherwise noted)
Parameter
A Version
B Version
1
Unit
Test Conditions/Comments
DC ACCURACY
Any Channel
Resolution
10
10
Bits
Minimum Resolution for Which No
Missing Codes are Guaranteed
10
10
Bits
Relative Accuracy
2
1
1
LSB max
This Spec Is Typical for V
DD
of
3.6 V to 5.5 V
Differential Nonlinearity
2
1
1
LSB max
This Spec Is Typical for V
DD
of
3.6 V to 5.5 V
Gain Error
2
3
3
LSB max
External Reference
10
10
LSB max
Internal Reference
Gain Error Match
2
0.6
0.6
LSB max
AD7417 Only
Offset Error
2
4
4
LSB max
Offset Error Match
0.7
0.7
LSB max
AD7417 Only
ANALOG INPUTS
Input Voltage Range
V
REF
V
REF
V max
0
0
V min
Input Leakage Current
3
1
1
A max
Input Capacitance
10
10
pF max
TEMPERATURE SENSOR
1
Measurement Error
Ambient Temperature 25
C
2
1
C max
T
MIN
to T
MAX
3
2
C max
Temperature Resolution
1/4
1/4
C/LSB
CONVERSION RATE
Track/Hold Acquisition Time
4
400
400
ns max
Source Impedance < 10
Conversion Time
Temperature Sensor
30
30
s max
Typically 27
s
Channels 1 to 4
15
15
s max
Typically 10
s
REFERENCE INPUT
5, 6
REF
IN
Input Voltage Range
6
2.625
2.625
V max
2.5 V + 5%
2.375
2.375
V min
2.5 V 5%
Input Impedance
40
40
k
min
Input Capacitance
10
10
pF max
ON-CHIP REFERENCE
Nominal 2.5 V
Reference Error
6
25
25
mV max
Temperature Coefficient
6
80
80
ppm/
C typ
DIGITAL INPUTS
Input High Voltage, V
IH
+V
S
0.7
+V
S
0.7
V min
Input Low Voltage, V
IL
+V
S
0.3
+V
S
0.3
V max
Input Leakage Current
1
1
A max
DIGITAL OUTPUTS
Output Low Voltage, V
OL
0.4
0.4
V max
I
OL
= 3 mA
Output High Current
1
1
A max
V
OH
= 5 V
POWER REQUIREMENTS
V
DD
5.5
5.5
V max
For Specified Performance
2.7
2.7
V min
I
DD
Logic Inputs = 0 V or V
DD
Normal Operation
600
600
A max
Power Down
1
1
A max
50 nA Typically
Auto Power-Down Mode
V
DD
= 3 V. See Operating Modes
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
REV. D
3
AD7416/AD7417/AD7418
NOTES
1
B version applies to AD7417 only with temperature range of 40
C to +85C. A version temperature range is 55C to +125C. For V
DD
= 2.7 V, T
A
= 85
C max
and temperature sensor measurement error =
3C.
2
See Terminology.
3
Refers to the input current when the part is not converting. Primarily due to reverse leakage current in the ESD protection diodes.
4
Sample tested during initial release and after any redesign or process change that may affect this parameter.
5
On-chip reference shuts down when external reference is applied.
6
The accuracy of the temperature sensor is affected by reference tolerance. The relationship between the two is explained in the section titled Temperature Sensor.
Specifications subject to change without notice.
(V
DD
= 2.7 V to 5.5 V, GND = 0 V, REF
IN
= 2.5 V, unless otherwise noted)
Parameter
Min
Typ
Max
Unit
Test Conditions/Comments
TEMPERATURE SENSOR AND ADC
Accuracy
2.0
C
T
A
= 25
C to +100C (V
DD
= 3 V min)
1
3.0
C
T
A
= 55
C to +125C (V
DD
= 3 V min)
1
Resolution
10
Bits
Temperature Conversion Time
40
s
Update Rate, t
R
400
s
OTI Delay
1
t
R
6
t
R
ms
Depends on Fault Queue Setting
Supply Current
1.0
mA
I
2
C Active
350
600
A
I
2
C Inactive
0.2
1.5
A
Shutdown Mode
T
OTI
Default Temperature
80
C
T
HYST
Default Temperature
75
C
DIGITAL INPUTS
Input High Voltage, V
IH
+V
S
0.7
+V
S
+ 0.5
V
Input Low Voltage, V
IL
0.3
+V
S
0.3 V
Input High Current, I
IH
0.005
1.0
A
V
IN
= 5 V
Input Low Current, I
IL
0.005
1.0
A
V
IN
= 0 V
Input Capacitance, C
IN
20
pF
All Digital Inputs
DIGITAL OUTPUTS
Output Low Voltage, V
OL
0.4
V
I
OL
= 3 mA
Output High Current
1
A
V
OH
= 5 V
Output Fall Time, t
f
250
ns
C
L
= 400 pF, I
O
= 3 mA
OS Output Low Voltage, V
OL
0.8
V
I
OUT
= 4 mA
AC ELECTRICAL CHARACTERISTICS
2
AD7416/AD7417/AD7418
Serial Clock Period, t
1
2.5
s
See Figure 1
Data In Setup Time to SCL High, t
2
50
ns
See Figure 1
Data Out Stable after SCL Low, t
3
0
ns
See Figure 1
SDA Low Setup Time to SCL Low
(Start Condition), t
4
50
ns
See Figure 1
SDA High Hold Time after SCL High
(Stop Condition), t
5
50
ns
See Figure 1
SDA and SCL Fall Time, t
6
300
ns
See Figure 1
NOTES
1
For V
DD
= 2.7 V to 3 V, T
A
max = 85
C and accuracy = 3C.
2
Sample tested during initial release and after any redesign or process change that may affect this parameter.
Specifications subject to change without notice.
t
4
t
2
t
3
t
5
SCL
SDA
DATA IN
SDA
DATA OUT
t
6
t
1
Figure 1. Diagram for Serial Bus Timing
AD7416SPECIFICATIONS
REV. D
AD7416/AD7417/AD7418
4
AD7417 PIN FUNCTION DESCRIPTION
Pin No.
Mnemonic
Description
1, 16
NC
No Connection. Do not connect anything to this pin.
2
SDA
Digital I/O. Serial Bus Bidirectional Data. Push-pull output.
3
SCL
Digital Input. Serial Bus Clock.
4
OTI
This is a logic output. The Over Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (temperature sensor) is greater than an 8-bit word in the Over Temperature Register (OTR).
The signal is reset at the end of a serial read operation. Open-drain output.
5
REF
IN
Reference Input. An external 2.5 V reference can be connected to the AD7417 at this pin. To enable
the on-chip reference the REF
IN
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/Hold, Comparator and Capacitor DAC, and Digital Circuitry.
710
A
IN1
to A
IN4
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 V
REF
.
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
V
DD
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/hold mode into hold mode and initiates a conversion. If the pulse is less
than 4
s, an internal timer ensures that the track/hold does not go into hold and conversion is not
initiated until the power-up time has elapsed. The track/hold goes into track mode again at the end of
conversion. (See Operating Mode section.)
AD7417 PIN CONFIGURATION
SOIC/TSSOP
TOP VIEW
(Not to Scale)
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
NC = NO CONNECT
NC
SDA
SCL
OTI
REF
IN
GND
A
IN1
A
IN2
NC
CONVST
V
DD
A0
A1
A2
A
IN4
A
IN3
AD7417
REV. D
AD7416/AD7417/AD7418
5
AD7416 PIN FUNCTION DESCRIPTION
Pin No.
Mnemonic
Description
1
SDA
Digital I/O. Serial Bus Bidirectional Data. Push-pull output.
2
SCL
Digital Input. Serial Bus Clock.
3
OTI
This is a logic output. The Over-Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Over-Temperature Register
(OTR). The signal is reset at the end of a serial read operation. Open-drain output.
4
GND
Ground reference for track/hold, comparator and capacitor DAC, and digital circuitry.
5
A2
Digital Input. The highest programmable bit of the Serial Bus Address.
6
A1
Digital Input. The middle programmable bit of the Serial Bus Address.
7
A0
Digital Input. The lowest programmable bit of the Serial Bus Address.
8
V
DD
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 Over-Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Over-Temperature Register
(OTR). The signal is reset at the end of a serial read operation. Open-drain output.
4
GND
Ground reference for track/hold, comparator and capacitor DAC, and digital circuitry.
5
A
IN
Analog Input Channel. The input channel is single-ended with respect to GND. The input channel
can convert voltage signals in the range 0 V to V
REF
. The analog input channel is selected by writing
to the configuration register of the AD7418 and choosing Channel 4. (See Control Byte section.)
6
REF
IN
Reference Input. An external 2.5 V reference can be connected to the AD7418 at this pin. To enable
the on-chip reference the REF
IN
pin should be tied to GND. If an external reference is connected to
the AD7418, the internal reference will shut down.
7
V
DD
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/hold mode into hold mode and initiates a conversion. If the pulse is
less than 4
s, an internal timer ensures that the track/hold does not go into hold and conversion is
not initiated until the power-up time has elapsed. The track/hold goes into track mode again at the
end of conversion. (See Operating Mode section.)
AD7416 PIN CONFIGURATION
SOIC/ SOIC
TOP VIEW
(Not to Scale)
8
7
6
5
1
2
3
4
SDA
SCL
OTI
GND
V
DD
A0
A2
AD7416
A1
AD7418 PIN CONFIGURATION
SOIC/ SOIC
TOP VIEW
(Not to Scale)
8
7
6
5
1
2
3
4
SDA
SCL
OTI
GND
CONVST
V
DD
REF
IN
A
IN
AD7418
REV. D
AD7416/AD7417/AD7418
6
ORDERING GUIDE
Temperature
Temperature
Package
Branding
Package
Model
Range
Error @ 25 C
Description
Information
Options
AD7416AR
55
C to +125C
2C
8-Lead Narrow Body (SOIC)
SO-8
AD7416ARM
55
C to +125C
2C
8-Lead
SOIC
C6A
RM-8
AD7417AR
55
C to +125C
2C
16-Lead Narrow Body (SOIC)
R-16A
AD7417ARU
55
C to +125C
2C
16-Lead (TSSOP)
RU-16
AD7417BR
40
C to +85C
1C
16-Lead Narrow Body (SOIC)
R-16A
AD7418AR
55
C to +125C
2C
8-Lead Narrow Body (SOIC)
SO-8
AD7418ARM
55
C to +125C
2C
8-Lead
SOIC
C7A
RM-8
ABSOLUTE MAXIMUM RATINGS
1
(T
A
= 25
C unless otherwise noted)
V
DD
to AGND . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 V to +7 V
V
DD
to DGND . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 V to +7 V
Analog Input Voltage to AGND
A
IN1
to A
IN4
. . . . . . . . . . . . . . . . . . . 0.3 V to V
DD
+ 0.3 V
Reference Input Voltage to AGND
2
. . . 0.3 V to V
DD
+ 0.3 V
Digital Input Voltage to DGND . . . . . . 0.3 V to V
DD
+ 0.3 V
Digital Output Voltage to DGND . . . . . 0.3 V to V
DD
+ 0.3 V
Operating Temperature Range
A Version . . . . . . . . . . . . . . . . . . . . . . . . . 55
C to +125C
B Version . . . . . . . . . . . . . . . . . . . . . . . . . . 40
C to +85C
Storage Temperature Range . . . . . . . . . . . . 65
C to +150C
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
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
SOIC 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
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent 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 condi-
tions 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 V
DD
pin. The
diagram below shows how the diode should be connected.
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, perma-
nent 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.
REF
IN
V
DD
AD7417
BAT81
WARNING!
ESD SENSITIVE DEVICE
REV. D
AD7416/AD7417/AD7418
7
(continued from page 1)
An I
2
C-compatible serial interface allows the AD7416/AD7417/
AD7418 registers to be written to and read back. The 3 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
SOIC packages.
PRODUCT HIGHLIGHTS
1. The AD7416/AD7417/AD7418 have an on-chip tempera-
ture sensor that allows an accurate measurement of the am-
bient temperature (
1C @ 25C, 2C over temperature)
to be made. The measurable temperature range is 55
C to
+125
C. An over-temperature indicator is implemented by
carrying out a digital comparison of the ADC code for
Channel 0 (temperature sensor) with the contents of the
on-chip over-temperature register.
2. The AD7417 offers a space saving 10-bit A/D solution with
four external voltage input channels, an on-chip temperature
sensor, an on-chip reference and clock oscillator.
3. The automatic power-down feature enables the AD7416/
AD7417/AD7418 to achieve superior power performance.
At slower throughput rates the part can be programmed to
operate in a low power shutdown mode allowing further
savings in power consumption.
TERMINOLOGY
Relative Accuracy
Relative accuracy or endpoint nonlinearity is the maximum
deviation from a straight line passing through the endpoints of
the ADC transfer function.
Differential Nonlinearity
This is the difference between the measured and the ideal
1 LSB change between any two adjacent codes in the ADC.
Offset Error
This is the deviation of the first code transition (0000 . . . 000)
to (0000 . . . 001) from the ideal, i.e., GND + 1 LSB.
Offset Error Match
This is the difference in Offset Error between any two channels.
Gain Error
This is the deviation of the last code transition (1111 . . . 110)
to (1111 . . . 111) from the ideal, i.e., VREF 1 LSB, after the
offset error has been adjusted out.
Gain Error Match
This is the difference in gain error between any two channels.
Track/Hold Acquisition Time
Track/hold acquisition time is the time required for the output
of the track/hold amplifier to reach its final value, within
1/2
LSB, after the end of conversion (the point at which the track/
hold returns to track mode). It also applies to situations where
a change in the selected input channel takes place or where
there is a step input change on the input voltage applied to the
selected A
IN
input of the AD7417 or AD7418. It means that
the user must wait for the duration of the track/hold acquisi-
tion time after the end of conversion or after a channel change/
step input change to A
IN
before starting another conversion,
to ensure that the part operates to specification.
CIRCUIT INFORMATION
The AD7417 and AD7418 are single- and four-channel, 15
s
conversion time, 10-bit A/D converters with on-chip tempera-
ture sensor, reference and serial interface logic functions on a
single chip. The AD7416 has no analog input channel and is
intended for temperature measurement only. The A/D converter
section consists of a conventional successive-approximation
converter based around a capacitor DAC. The AD7416, AD7417,
and AD7418 are capable of running on a 2.7 V to 5.5 V power
supply and the AD7417 and AD7418 accept an analog input
range of 0 V to +VREF. The on-chip temperature sensor allows
an accurate measurement of the ambient device temperature to
be made. The working measurement range of the temperature
sensor is 55
C to +125C. The parts require a 2.5 V reference
which 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 no external clock is required except when reading
from and writing to the serial port. The on-chip track/hold goes
from track to hold mode and the conversion sequence is started
on the falling edge of the
CONVST signal. A conversion is also
initiated in the automatic conversion mode every time a read or
write operation to the AD7416/AD7417/AD7418 takes place. In
this case, the internal clock oscillator (which runs the automatic
conversion sequence) is restarted at the end of the read or write
operation. The track/hold goes into hold approximately 3
s
after the read or write operation is complete and a conversion is
then initiated. The result of the conversion is available either
15
s or 30 s later, depending on whether an analog input
channel or the temperature sensor is selected. The track/hold
acquisition time of the AD7417/AD7418 is 400 ns.
A temperature measurement is made by selecting the Channel 0
of the on-chip MUX and carrying out a conversion on this
channel. A conversion on Channel 0 takes 30
s to complete.
Temperature measurement is explained in the Temperature
Measurement section of this data sheet.
The on-chip reference is not available to the user, but REF
IN
can be overdriven by an external reference source (2.5 V only).
The effect of reference tolerances on temperature measurements
is discussed in the Reference section of the data sheet.
All unused analog inputs should be tied to a voltage within the
nominal analog input range to avoid noise pickup. For mini-
mum power consumption, the unused analog inputs should be
tied to GND.
REV. D
AD7416/AD7417/AD7418
8
TYPICAL CONNECTION DIAGRAM
Figure 2 shows a typical connection diagram for the AD7417.
Using the A0, A1 and A2 pins allows the user to select from up
to eight AD7417s on the same serial bus, if desired. An external
2.5 V reference can be connected at the REF
IN
pin. If an exter-
nal reference is used, a 10
F capacitor should be connected
between REF
IN
and GND. SDA and SCL form the two-wire
I
2
C-compatible interface. For applications where power con-
sumption is of concern, the automatic power-down at the end of
a conversion should be used to improve power performance. See
Operating Modes section of the data sheet.
V
DD
AIN1
GND
REF
IN
SUPPLY
2.7V TO
5.5V
0.1 F
10 F
10 F FOR
EXTERNAL
REFERENCE
OPTIONAL
EXTERNAL
REFERENCE
AD780/
REF-192
0V TO 2.5V
INPUT
CONVST
SDA
AIN2
AIN3
AIN4
OTI
SCL
TWO-WIRE
SERIAL
INTERFACE
AD7417
A0
A1
A2
C/ P
Figure 2. Typical Connection Diagram
ANALOG INPUTS
Figure 3 shows an equivalent circuit of the analog input struc-
ture 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 prima-
rily be attributed to pin capacitance. The resistor R1 is a
lumped component made up of the on resistance of a multi-
plexer and a switch. This resistor is typically about 1
k
. The
capacitor C1 is the ADC sampling capacitor and has a capaci-
tance of 3 pF.
A
IN
D1
C1
3pF
V
DD
D2
C2
4pF
V
BALANCE
CONVERT PHASE SWITCH OPEN
TRACK PHASE SWITCH CLOSED
R1
1k
Figure 3. Equivalent Analog Input Circuit
ON-CHIP REFERENCE
The AD7416/AD7417/AD7418 has an on-chip 1.2 V band-gap
reference which is gained up by a switched capacitor amplifier to
give an output of 2.5 V. The amplifier is only powered up at the
start of the conversion phase and is powered down at the end of
the conversion. The on-chip reference is selected by connecting
the REF
IN
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
REF
IN
pin. This has the effect of shutting down the on-chip
reference circuitry.
1.2V
REF
IN
SW1
2.5V
EXTERNAL
REFERENCE
DETECT
BUFFER
1.2V
26k
24k
+
+
Figure 4. On-Chip Reference
INTERNAL REGISTER STRUCTURE
The AD7417/AD7418 has seven internal registers, as shown in
Figure 5. Six of these are data registers and one is an address
pointer register. The AD7416 has five internal registers (the
ADC and Config2 registers are not applicable to the AD7416).
T
HYST
SET-POINT
REGISTER
(READ/WRITE
ADDRESS 02H)
CONFIGURATION
REGISTER
(READ/WRITE
ADDRESS 01H)
T
OTI
SET-POINT
REGISTER
(READ/WRITE
ADDRESS 03H)
SERIAL
BUS
INTERFACE
SCL
TEMPERATURE
VALUE
REGISTER
(READ-ONLY
ADDRESS 00H)
ADDRESS POINTER
REGISTER
(SELECTS DATA REGISTER
FOR READ/WRITE)
ADDRESS
DATA
CONFIG 2
REGISTER
(READ/WRITE
ADDRESS 05H)
ADC
REGISTER
(READ ONLY
ADDRESS 04H)
SDA
Figure 5. AD7417/AD7418 Register Structure
ADDRESS POINTER REGISTER
The Address Pointer Register is an 8-bit register which stores an
address that points to one of the six data registers. The first data
byte of every serial write operation to the AD7416/AD7417/
AD7418 is the address of one of the data registers, which is
stored in the Address Pointer Register, and selects the data
register to which subsequent data bytes are written. Only the
three LSBs of this register are used to select a data register.
REV. D
AD7416/AD7417/AD7418
9
Table V. Configuration Register
D7
D6
D5
D4
D3
D2
D1
D0
Channel
Fault
OTI
Cmp/
Shut-
Selection
Queue
Polarity
Int
down
The AD7416 contains a temperature-only channel, the AD7417
has four analog input channels and a temperature channel, while
the AD7418 has two channels, a temperature channel and an
analog input channel. The temperature channel address for all
parts is the same, CH0. The address for the analog input channel
on the AD7418 is CH4. Table VI outlines the channel selection
on the parts, while Table VII shows the fault queue settings. D1
and D2 are explained in the OTI Output section.
Table VI. Channel Selection
D7
D6
D5
Channel Selection
0
0
0
Temperature Sensor (All Parts)
0
0
1
AIN1 (AD7417 Only)
0
1
0
AIN2 (AD7417 Only)
0
1
1
AIN3 (AD7417 Only)
1
0
0
AIN4 (AD7417) and AIN (AD7418)
Table VII. Fault Queue Settings
D4
D3
Number of Faults
0
0
1 (Power-Up Default)
0
1
2
1
0
4
1
1
6
T
HYST
SETPOINT REGISTER (ADDRESS 02H)
The T
HYST
Setpoint Register is a 16-bit, read/write register
whose 9 MSBs store the T
HYST
setpoint in two's complement
format equivalent to the 9 MSBs of the temperature value regis-
ter. Bits 6 to 0 are unused.
T
OTI
SETPOINT REGISTER (ADDRESS 03H)
The T
OTI
Setpoint Register is a 16-bit, read/write register whose
9 MSBs store the T
OTI
setpoint in two's complement format
equivalent to the 9 MSBs of the temperature value register. Bits
6 to 0 are unused.
Table VIII. Setpoint Registers
D15
D14
D13
D12
D11
D10
D9
D8
D7
MSB
B7
B6
B5
B4
B3
B2
B1
LSB
ADC VALUE REGISTER (ADDRESS 04H)
The ADC value register is a 16-bit, read only register whose
10 MSBs store the value produced by the ADC in binary for-
mat. Bits 5 to 0 are unused. Table IX shows the ADC value
register with 10 MSBs containing the ADC conversion request.
Table IX.
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
MSB B8
B7
B6
B5
B4
B3
B2
B1
LSB
Table I. Address Pointer Register
P7
*
P6
*
P5
*
P4
*
P3
*
P2
P1
P0
0
0
0
0
0
Register Select
*P3 to P7 must be set to 0.
Table II. Register Addresses
P2
P1
P0
Registers
0
0
0
Temperature Value (Read Only)
0
0
1
Config Register (Read/Write)
0
1
0
T
HYST
(Read/Write)
0
1
1
T
OTI
1
0
0
ADC (AD7417/AD7418 Only)
1
0
1
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 two's complement format. Bits 5 to 0 are unused.
Table III. Temperature Value Register
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
MSB B8
B7
B6
B5
B4
B3
B2
B1
LSB
The temperature data format is shown in Table IV. This shows
the full theoretical range of the ADC from 128
C to +127C,
but in practice the temperature measurement range is limited to
the operating temperature range of the device.
Table IV. 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
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 01H)
The Configuration Register is an 8-bit, read/write register
that is used to set the operating modes of the AD7416/AD7417/
AD7418. Bits D7 to D5 control the channel selection as out-
lined 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 com-
parator or interrupt mode of operation, and D0 = 1 selects
shutdown mode (Default D0 = 0).
REV. D
AD7416/AD7417/AD7418
10
ADC Transfer Function
The designed code transitions occur at successive integer LSB
values (i.e., 1 LSB, 2 LSB, etc.). The LSB size is = REF/1024.
The ideal transfer function characteristic for the AD7417 and
AD7418 ADC is shown in Figure 6.
111...111
111...110
111...000
011...111
000...010
000...001
000...000
ADC CODE
0V 1/2LSB
+V
REF
1LSB
ANALOG INPUT
1LSB = V
REF
/1024
Figure 6.
CONFIG2 REGISTER (ADDRESS 05H)
A second configuration register is included in the AD7417/
AD7418 for the functionality of the
CONVST pin. It is an 8-bit
register with bits D5 to D0 being left at 0. Bit D7 determines
whether the AD7417/AD7418 should be operated in its default
mode (D7 = 0), performing conversions every 355
s or in
CONVST pin mode (D7 = 1), where conversions will start only
when the
CONVST pin is used. Bit 6 contains the Test 1 bit.
When this bit is 0 the I
2
C filters are enabled (default). A 1
disables the filters.
Table X.
D7
D6
D5
D4
D3
D2
D1
D0
Conversion Mode
Test 1 0
0
0
0
0
0
SERIAL BUS INTERFACE
Control of the AD7416/AD7417/AD7418 is carried out via the
I
2
C-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 I
2
C-compatible devices, the AD7416/AD7417/AD7418
have a 7-bit serial address. The four MSBs of this address for
the AD7416 are set to 1001, the AD7417 are 0101, while the
three LSBs can be set by the user by connecting the A2 to A0
pins to either +V
S
or GND. By giving them different addresses,
up to eight AD7416/AD7417s can be connected to a single
serial bus, or the addresses can be set to avoid conflicts with
other devices on the bus. The four MSBs of this address for the
AD7418 are 0101, while the three LSBs are all set to zero.
If a serial communication occurs during a conversion operation,
the conversion will stop and will restart after the communication.
The serial bus protocol operates as follows:
1. The master initiates data transfer by establishing a START
condition, defined as a high-to-low transition on the serial
data line SDA while the serial clock line SCL remains high.
This indicates that an address/data stream will follow. All
slave peripherals connected to the serial bus respond to the
START condition, and shift in the next eight bits, consisting
of a 7-bit address (MSB first) plus a R/
W bit, which deter-
mines the direction of the data transfer, i.e., whether data
will be written to or read from the slave device.
The peripheral whose address corresponds to the transmitted
address responds by pulling the data line low during the low
period before the ninth clock pulse, known as the 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 will write to the
slave device. If the R/
W bit is a 1 the master will read from
the slave device.
2. Data is sent over the serial bus in sequences of nine clock
pulses, eight bits of data followed by an Acknowledge Bit
from the receiver of data. Transitions on the data line must
occur during the low period of the clock signal and remain
stable during the high period, as a low-to-high transition
when the clock is high may be interpreted as a STOP signal.
3. When all data bytes have been read or written, stop condi-
tions are established. In WRITE mode, the master will pull
the data line high during the 10th clock pulse to assert a
STOP condition. In READ mode, the master device will pull
the data line high during the low period before the 9th clock
pulse. This is known as No Acknowledge. The master will
then take the data line low during the low period before the
10th clock pulse, then high during the 10th clock pulse to
assert a STOP condition.
Any number of bytes of data may be transferred over the serial
bus in one operation, but it is not possible to mix read and write
in one operation, because the type of operation is determined at
the beginning and cannot subsequently be changed without
starting a new operation.
REV. D
AD7416/AD7417/AD7418
11
WRITING TO THE AD7416/AD7417/AD7418
Depending on the register being written to, there are three dif-
ferent writes for the AD7416/AD7417/AD7418.
1. Writing to the Address Pointer Register for a subsequent read.
In order to read data from a particular register, the Address
Pointer Register must contain the address of that register. If
it does not, the correct address must be written to the Address
Pointer Register by performing a single-byte write operation,
as shown in Figure 7. The write operation consists of the
serial bus address followed by the address pointer byte. No
data is written to any of the data registers.
2. Writing a single byte of data to the Configuration Registers
or T
OTI
, T
HYST
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 T
OTI
and T
HYST
, and only eight bits need be written to the
T
OTI
and T
HYST
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,
written to the selected data register. This is illustrated in
Figure 8.
3. Writing two bytes of data to the T
OTI
or T
HYST
Register.
If 9-bit resolution is required for the temperature setpoints,
then two bytes of data must be written to the T
OTI
and
T
HYST
registers. This consists of the serial bus address, the
register address, written to the address pointer register, fol-
lowed by two data bytes written to the selected data register.
This is illustrated in Figure 9.
R/
W
1
SCL
SDA
0
0
1
A2
A1
A0
P7
P6
P5
P4
P3
P2
P1
P0
ACK. BY
AD7416
STOP BY
MASTER
START BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
1
9
1
ACK. BY
AD7416
9
Figure 7. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation
R/
W
1
SCL
SDA
0
0
1
A2
A1
A0
P7
P6
P5
P4
P3
P2
P1
P0
ACK. BY
AD7416
START BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
1
9
1
ACK. BY
AD7416
9
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
AD7416
STOP BY
MASTER
FRAME 3
DATA BYTE
1
9
SCL (CONTINUED)
SDA (CONTINUED)
Figure 8. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register
REV. D
AD7416/AD7417/AD7418
12
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 Configura-
tion Register is a single byte read operation, as shown in Figure
10, the register address previously having been set by a single-
byte write operation to the address pointer register.
Reading data from the temperature value, T
OTI
, or T
HYST
regis-
ters is a two-byte operation, as shown in Figure 11. It is also
possible to read the most significant bit of a 9-/10-bit register in
this manner.
OTI OUTPUT
The OTI output has two operating modes, which are selected by
Bit D1 of the Configuration Register. In the comparator mode,
(D1 = 0), the OTI output becomes active when the temperature
exceeds T
OTI
, and remains active until the temperature falls
below T
HYST
. This mode allows the AD7416/AD7417/AD7418
to be used as a thermostat, for example to control the operation
of a cooling fan.
R/
W
1
SCL
SDA
0
0
1
A2
A1
A0
P7
P6
P5
P4
P3
P2
P1
P0
ACK. BY
AD7416
START BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
1
9
1
ACK. BY
AD7416
9
D15
D14
D13
D12
D11
D10
D9
D8
ACK. BY
AD7416
STOP BY
MASTER
FRAME 3
MOST SIGNIFICANT DATA BYTE
1
9
SCL
(CONTINUED)
SDA
(CONTINUED)
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
AD7416
STOP BY
MASTER
FRAME 4
LEAST SIGNIFICANT DATA BYTE
1
9
Figure 9. Writing to the Address Pointer Register Followed by a Two Bytes of Data to the T
OTI
or T
HYST
Register
SDA
NO ACK. BY
MASTER
START BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
SINGLE DATA BYTE FROM AD7416
ACK. BY
AD7416
1
9
1
9
D7
D6
D5
D4
D3
D2
D1
D0
R/
W
A0
A1
A2
1
0
1
SCL
STOP BY
MASTER
0
Figure 10. Reading a Single Byte of Data from the Configuration Register
R/
W
1
SCL
SDA
0
0
1
A2
A1
A0
D15
D14
D13
D12
D10
D11
D9
D8
ACK. BY
MASTER
START BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
MOST SIGNIFICANT DATA BYTE FROM AD7416
1
9
1
ACK. BY
AD7416
9
D7
D6
D5
D4
D3
D2
D1
D0
NO ACK. BY
MASTER
STOP BY
MASTER
FRAME 3
LEAST SIGNIFICANT DATA BYTE FROM AD7416
1
9
SCL (CONTINUED)
SDA (CONTINUED)
Figure 11. Reading Two Bytes of Data from T
OTI
or T
HYST
Register
REV. D
AD7416/AD7417/AD7418
13
T
OTI
T
HYST
OTI OUTPUT
COMPARATOR
MODE
OTI OUTPUT
INTERRUPT
MODE
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 12. Operation of OTI Output (Shown Active Low)
The open-drain configuration of OTI allows the OTI outputs of
several AD7416/AD7417/AD7418s to be wire-ANDed together
when in active low mode.
The OTI output is used to indicate that an out-of-limit tem-
perature excursion has occurred. OTI is an open-drain output
that can be programmed to be active low by setting Bit D2 of
the Configuration Register to 0, or active high by setting Bit D2
of the Configuration Register to 1.
In the Interrupt mode (D1 = 1), the OTI output becomes active
when the temperature exceeds T
OTI
, and remains active even if
the temperature falls below T
HYST
, until it is reset by a read opera-
tion. Once OTI has become active by the temperature exceeding
T
OTI
, then been reset, it will remain inactive even if the tempera-
ture remains, or subsequently rises again, above T
OTI
. It will not
become active again until the temperature falls below T
HYST
. It
will then remain active until reset by a read operation. Once OTI
has become active by the temperature falling below T
HYST
, then
been reset, it will remain inactive even if the temperature remains,
or subsequently falls again, below T
HYST
.
OTI is also reset when the AD7416/AD7417/AD7418 is placed
in shutdown mode, by setting bit D0 of the Configuration Regis-
ter to 1.
The OTI output requires an external pull-up resistor. This can
be connected to a voltage different from +V
S
(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 tempera-
ture reading. The maximum value of pull-up resistor that will meet
the output high current specification of the OTI output is 30 k
, but
higher values may be used if a lower output current is required.
For most applications a value of 10 k
will prove suitable.
FAULT QUEUE
To avoid false triggering of the AD7416/AD7417/AD7418 in
noisy environments, a fault queue counter is provided, which
can be programmed by Bits D3 and D4 of the Configuration
Register (see Table V) to count 1, 2, 4, or 6 fault events before
OTI becomes active. In order to trigger OTI, the faults must
occur consecutively. For example, if the fault queue is set to 4,
then four consecutive temperature measurements greater than
T
OTI
(or less than T
HYST
) must occur. Any reading that breaks
the sequence will reset the fault queue counter, so if there are
three readings greater than T
OTI
followed by a reading less than
T
OTI
, the fault queue counter will be reset without triggering OTI.
POWER-ON DEFAULTS
The AD7416/AD7417/AD7418 always powers up with the
following defaults:
Address pointer pointing to Temperature Value Register
Comparator mode:
T
OTI
= 80
C
T
HYST
= 75
C
OTI Active LOW
Fault Queue = 1
These default settings allow the AD7416/AD7417/AD7418 to
be used as a stand-alone thermostat without any connection to a
serial bus.
OPERATING MODES
The AD7416/AD7417/AD7418 has two possible modes of
operation depending on the value of D0 in the Configuration
Register.
Mode 1
Normal operation of the AD7416/AD7417/AD7418 occurs when
D0 = 0. In this active mode, a conversion takes place every
400
s. Once the conversion has taken place, the part partially
powers down, consuming typically 350
A of current until the
next conversion occurs.
Two situations can arise in this mode on the request of a
temperature read. If a read occurs during a conversion, the
conversion aborts and a new one starts on the Stop/Repeat start
condition. The temperature value that is read is that of the
previous completed conversion. The next conversion will typically
occur 400
s 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
s.
With a V
DD
= 3 V, for each 400
s cycle, the AD7416 spends
40
s (or 10% of the time) in conversion mode. It spends 360 s
(or 90% of time) in partial power-down mode. Thus the average
power dissipated by the AD7416/AD7417/AD7418 is:
3 mW
0.1 + 1 mW 0.9 = 1.2 mW
Mode 2
For applications where temperature measurements are required
at a slower rate e.g., every second, power consumption of the part
can be reduced by writing to the part to go to a full power-down
between reads. The current consumption in full power-down is
typically 0.2
A and full power-down is initiated when D0 = 1
in the configuration register. When a measurement is required, a
write operation can be performed to power-up the part. The
part then performs a conversion and is returned to power-down.
The temperature value can be read in the full power-down
because the I
2
C bus is continuously active.
The power dissipation in this mode depends on the rate at
which reads take place. Taking the requirements for a tempera-
ture 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
s
and putting it into full power-down again. In this case the aver-
age power consumption is calculated as follows. The part spends
40
s (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 dissi-
pation. Thus the average power dissipation is:
3 mW
0.004 + 60 nW 0.9996 = 1.2
W
REV. D
AD7416/AD7417/AD7418
14
The fastest throughput rate at which the AD7416/AD7417/
AD7418 can be operated is 2.5 kHz (i.e., a read every 400
s
conversion period). Since T
OTI
and T
HYST
are two byte reads,
the read time with the I
2
C operating at 100 kbit/s would be
270
s. If temperature reads are called too often, reads will
overlap with conversions, aborting them continuously, which
results in invalid readings.
CONVERT START MODE
The AD7417/AD7418 has an extra mode, set by writing to the
MSB of the Config2 Register.
CONVST Pin Mode
By setting the
CONVST mode bit to 1, conversions are initiated
only by using the
CONVST pin. In this method of operation,
CONVST is normally low.
The rising edge of
CONVST starts the power-up time. This
power-up time is 4
s. If the CONVST high time is longer
than 4
s, a conversion is initiated on the falling edge of CONVST
and the track/hold also enters its hold mode at this time. If the
CONVST high time is less than 4
s, an internal timer, initi-
ated by the rising edge of
CONVST holds off the track/hold and
the initiation of conversion until timer times out (4
s after the
rising edge of
CONVST, which corresponds with the power-up
time).
CONVST input remains low at the end of conversion, thus
causing the part to enter its power-down mode. In this method
of operation,
CONVST is normally low with a high-going pulse
controlling the power-up and conversion starts.
The
CONVST pin should not be pulsed when reading from or
writing to the port.
Figure 16 shows the recommended minimum times for the
CONVST pulse when the temperature channel is selected. Figure 17
shows the minimum times an analog input channel is selected.
APPLICATIONS INFORMATION
SUPPLY DECOUPLING
The AD7416/AD7417/AD7418 should be decoupled with a
0.1
F ceramic capacitor between +V
S
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 V
DD
pin is at 0 V. Reference application note
AN-588 for more information.
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 tempera-
ture being measured.
The ground pin provides the best thermal path to the die, so the
temperature of the die will be close to that of the printed circuit
ground track. Care should be taken to ensure that this is in good
thermal contact with the surface being measured.
As with any IC, the AD7416/AD7417/AD7418 and its associ-
ated wiring and circuits must be kept free from moisture to
prevent leakage and corrosion, particularly in cold conditions
where condensation is more likely to occur. Water resistant
varnishes and conformal coatings can be used for protection.
The small size of the AD7416 package allows it to be mounted
inside sealed metal probes, which provide a safe environment for
the device.
FAN CONTROLLER
Figure 13 shows a simple fan controller that will switch on a
cooling fan when the temperature exceeds 80
C, and switch it
off again when the temperature falls below 75
C. The AD7416
can be used stand-alone in this application, or with a serial bus
interface if different trip temperatures are required. If the AD7416
is used with a bus interface, the sense of OTI can be set to
active high, Q1 and R1 can be omitted, and OTI connected
directly to the gate of Q2, with R2 as the pull-up resistor.
+V
S
3V TO 5.5V
AD7416
R1
10k
Q1
2N3904
OR SIMILAR
R2
10k
Q2
LOGIC LEVEL
MOSFET RATED
TO SUIT FAN
CURRENT
12V
Figure 13. AD7416 Used as a Fan Controller
REV. D
AD7416/AD7417/AD7418
15
THERMOSTAT
Figure 14 shows the AD7416 used as a thermostat. The heater
will be switched on when the temperature falls below T
HYST
,
and switched off again when the temperature rises above T
OS
.
For this application, the OTI output should be programmed
active low, and for comparator mode.
+V
S
3V TO 5.5V
AD7416
R1
10k
Q1
2N3904
OR SIMILAR
RELAY
D1
1N4001
HEATER
HEATER
SUPPLY
RLA1
Figure 14. AD7416 Used as a Thermostat
SYSTEM WITH MULTIPLE AD7416s
The three LSBs of the AD7416's serial address can be set by
the user, allowing eight different addresses from 1001000 to
1001111. Figure 15 shows a system in which eight AD7416s are
connected to a single serial bus, with their OTI outputs wire
ANDed together to form a common interrupt line. This arrange-
ment 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.
PROCESSOR
AD7416
SUPER I/O CHIP
AD7416
AD7416
AD7416
AD7416
AD7416
AD7416
AD7416
+V
S
3V TO 5.5V
R1
10k
Figure 15. Multiple Connection of AD7416s to a Single Serial Bus
100ns
40 s
CONVST
Figure 16.
CONVST When Temperature Channel Selected
100ns
15 s
CONVST
Figure 17.
CONVST When V
IN
Channel(s) Selected
REV. D
AD7416/AD7417/AD7418
16
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
C0112602/02(D)
PRINTED IN U.S.A.
16-Lead Thin Shrink Small Outline Package
(TSSOP) (RU-16)
16
9
8
1
0.201 (5.10)
0.193 (4.90)
0.256 (6.50)
0.246 (6.25)
0.177 (4.50)
0.169 (4.30)
PIN 1
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
0.0118 (0.30)
0.0075 (0.19)
0.0256
(0.65)
BSC
0.0433
(1.10)
MAX
0.0079 (0.20)
0.0035 (0.090)
0.028 (0.70)
0.020 (0.50)
8
0
16-Lead Narrow Body (SOIC)
(R-16A)
16
9
8
1
0.3937 (10.00)
0.3859 (9.80)
0.2440 (6.20)
0.2284 (5.80)
0.1574 (4.00)
0.1497 (3.80)
PIN 1
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.0688 (1.75)
0.0532 (1.35)
0.0500
(1.27)
BSC
0.0099 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8
0
0.0196 (0.50)
0.0099 (0.25)
x 45
8-Lead Narrow Body (SOIC)
(R-8)
0.0098 (0.25)
0.0040 (0.10)
0.1574 (4.00)
0.1497 (3.80)
0.1968 (5.00)
0.1890 (4.80)
8
5
4
1
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.0688 (1.75)
0.0532 (1.35)
SEATING
PLANE
0.0192 (0.49)
0.0138 (0.35)
0.0500
(1.27)
BSC
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8
0
0.0196 (0.50)
0.0099 (0.25)
x 45
8-Lead SOIC Package
(RM-8)
8
5
4
1
0.122 (3.10)
0.114 (2.90)
0.199 (5.05)
0.187 (4.75)
PIN 1
0.0256 (0.65) BSC
0.122 (3.10)
0.114 (2.90)
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
0.018 (0.46)
0.008 (0.20)
0.043 (1.09)
0.037 (0.94)
0.120 (3.05)
0.112 (2.84)
0.011 (0.28)
0.003 (0.08)
0.028 (0.71)
0.016 (0.41)
33
27
0.120 (3.05)
0.112 (2.84)
Revision History
Location
Page
Data Sheet changed from REV. C to REV. D.
Edits to SPECIFICATIONS headings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Edits to SERIAL BUS ADDRESS section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Edits to Figure 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Edits to
CONVST Pin Mode section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Addition of two new figures (16 and 17) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
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