Page 1
10-Bit Digital Temperature Sensor (AD7416) and
a
Single/Four-Channel ADC (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: –55ⴗC to +125ⴗC
On-Chip Track/Hold
Over-Temperature Indicator
Automatic Power Down at the End of a Conversion
Wide Operating Supply Range: +2.7 V to +5.5 V
2C®
Compatible Serial Interface
I
Selectable Serial Bus Address Allows Connection of Up
to Eight AD7416/AD7417s to a Single Bus
AD7416 is a Superior Replacement for LM75
APPLICATIONS
Data Acquisition with Ambient Temperature Monitoring
Industrial Process Control
Automotive
Battery Charging Applications
Personal Computers
GENERAL DESCRIPTION
The AD7417 and AD7418 are 10-bit, single- and 4-channel
A/D converter with an on-chip temperature sensor that can
operate from a single +2.7 V to +5.5 V power supply. The de-
vices contain a 15 µs successive-approximation converter, a
5-channel multiplexer, a temperature sensor, a clock oscillator,
a track/hold, and a reference (+2.5 V). The AD7416 is a 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 Over-Temperature
Indicator output (OTI) is provided, which becomes active when a
programmed limit is exceeded.
A configuration register allows programming of the sense of the
OTI output (active high or active low) and its operating mode
(comparator or interrupt). A programmable fault queue counter
allows the number of out of limit measurements that must occur
before triggering the OTI output to be set, to prevent spurious
triggering of the OTI output in noisy environments.
(continued on page 7)
V
IN1
V
IN2
V
IN3
V
IN4
V
IN1
A0
A1
A2
AD7416/AD7417/AD7418
FUNCTIONAL BLOCK DIAGRAMS
BANDGAP
TEMPERATURE
SENSOR
ADDRESS
POINTER
REGISTER
TEMP
SENSOR
MUX
NC NC GND
NC = NO CONNECT
V
DD
TEMP
SENSOR
MUX
REF
REF
2.5V
SAMPLING
CAPACITOR
REF
REF
2.5V
SAMPLING
CAPACITOR
10-BIT
ANALOG-DIGITAL
CONVERTER
TEMPERATURE
VALUE
REGISTER
T
SETPOINT
OTI
REGISTER
T
SETPOINT
HYST
REGISTER
CONFIGURATION
REGISTER
SERIAL BUS
INTERFACE
IN
OVER-TEMP REG
DISTRIBUTION
CLOCK
V
BALANCE
CONVST
IN
OVER-TEMP REG
DISTRIBUTION
CLOCK
V
DD
CHARGE
DAC
CONTROL
+
CHARGE
DAC
CONTROL
+
LOGIC
LOGIC
AD7416
SETPOINT
COMPARATOR
FAULT
QUEUE
COUNTER
A > B
B
A
DATA OUT
I2C
INTERFACE
AD7417
A > B
B
A
DATA OUT
I2C
INTERFACE
A2A1A0
+V
OTI
GND
SDA
SCL
OTI
SCL
SDA
OTI
SCL
SDA
S
I2C is a registered trademark of Philips Corporation.
REV. B
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
AD7418
AGND
V
BALANCE
CONVST
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 1999
Page 2
AD7416/AD7417/AD7418
(VDD = +2.7 V to +5.5 V, GND = 0 V, REFIN = +2.5 V, unless other-
AD7417/AD7418–SPECIFICATIONS
Parameter A Version B Version
DC ACCURACY Any Channel
Resolution 10 10 Bits
Minimum Resolution for Which No
Missing Codes are Guaranteed 10 10 Bits
Relative Accuracy
Differential Nonlinearity
Gain Error
Gain Error Match
Offset Error
Offset Error Match ±0.7 ±0.7 LSB max AD7417 Only
ANALOG INPUTS
Input Voltage Range V
Input Leakage Current
Input Capacitance 10 10 pF max
TEMPERATURE SENSOR
Measurement Error
Ambient Temperature +25°C ±2 ±1 °C max
to T
T
MIN
Temperature Resolution 1/4 1/4 °C/LSB
CONVERSION RATE
Track/Hold Acquisition Time
Conversion Time
Temperature Sensor 30 30 µs max
Channels 1 to 4 15 15 µs max
REFERENCE INPUT
REFIN Input Voltage Range
Input Impedance 40 40 kΩ min
Input Capacitance 10 10 pF max
ON-CHIP REFERENCE Nominal 2.5 V
Reference Error
Temperature Coefficient
DIGITAL INPUTS
Input High Voltage, V
Input Low Voltage, V
Input Leakage Current 1 1 µA max
DIGITAL OUTPUTS
Output Low Voltage, V
Output High Current 1 1 µA max V
POWER REQUIREMENTS
V
DD
7
I
DD
Normal Operation 600 600 µA max
Power Down 1 1 µA max 50 nA Typically
Auto Power-Down Mode V
10 sps Throughput Rate 6 6 µW typ
1 ksps Throughput Rate 60 60 µW typ
10 ksps Throughput Rate 600 600 µW typ
Power Down 3 3 µW max Typically 0.15 µW
2
2
MAX
2
2
±1 ±1 LSB max This Spec Is Typical for V
±1 ±1 LSB max This Spec Is Typical for V
±3 ±3 LSB max External Reference
2
±10 ±10 LSB max Internal Reference
±0.6 ±0.6 LSB max AD7417 Only
±4 ±4 LSB max
␣V
REF
3
1
0␣ 0␣ V min
±1 ±1 µA max
±3 ±2 °C max
4
5, 6
6
400 400 ns max Source Impedance < 10 Ω
2.625 2.625 V max 2.5 V + 5%
2.375 2.375 V min 2.5 V – 5%
6
6
IH
IL
OL
±25 ±25 mV max
80 80 ppm/°C typ
+V
× 0.7 +VS × 0.7 V min
S
+V
× 0.3 +VS × 0.3 V max
S
0.4 0.4 V max I
+5.5 +5.5 V max For Specified Performance
+2.7 +2.7 V min
wise noted)
1
Units Test Conditions/Comments
␣V max
REF
+3.6 V to +5.5 V
+3.6 V to +5.5 V
= 3 µA
OL
= 5 V
OH
Logic Inputs = 0 V or V
= 3 V. See Operating Modes
DD
DD
DD
DD
of
of
–2–
REV. B
Page 3
AD7416/AD7417/AD7418
NOTES
1
B version applies to AD7417 only with temperature range of –40°C to +85°C. A version temperature range is –55°C to +125°C. For V
and temperature sensor measurement error = ±3°C.
2
See Terminology.
3
Refers to the input current when the part is not converting. Primarily due to reverse leakage current in the ESD protection diodes.
4
Sample tested during initial release and after any redesign or process change that may affect this parameter.
5
On-chip reference shuts down when external reference is applied.
6
The accuracy of the temperature sensor is affected by reference tolerance. The relationship between the two is explained in the section titled Temperature Sensor.
7
The AD7417 and AD7418 IDD is typically 1 mA when the parts are set for external CONVST Mode and CONVST is held high.
Specifications subject to change without notice.
= +2.7 V, T
DD
= +85°C max
A
AD7416–SPECIFICATIONS
(VDD = +2.7 V to +5.5 V, GND = 0 V, REFIN = +2.5 V, unless otherwise noted)
Parameter Min Typ Max Units Test Conditions/Comments
TEMPERATURE SENSOR AND ADC
Accuracy ±2.0 °CT
±3.0 °CT
= –25°C to +100°C (V
A
= –55°C to +125°C (V
A
= 3 V min)
DD
= 3 V min)
DD
Resolution 10 Bits
Temperature Conversion Time 40 µs
Update Rate, t
OTI Delay 1 × t
R
R
Supply Current 1.0 mA I
400 µs
6 × t
R
350 600 µAI
ms Depends on Fault Queue Setting
2
C Active
2
C Inactive
0.2 1.5 µA Shutdown Mode
T
Default Temperature 80 °C
OTI
T
Default Temperature 75 °C
HYST
DIGITAL INPUTS
Input High Voltage, V
Input Low Voltage, V
IL
Input High Current, I
Input Low Current, I
Input Capacitance, C
IL
IN
IH
IH
+V
× 0.7 +V
S
–0.3 +V
0.005 1.0 µAV
–0.005 –1.0 µAV
20 pF All Digital Inputs
+ 0.5 V
S
× 0.3 V
S
= 5 V
IN
= 0 V
IN
DIGITAL OUTPUTS
Output Low Voltage, V
OL
Output High Current 1 mA V
Output Fall Time, t
OS Output Low Voltage, V
AC ELECTRICAL CHARACTERISTICS
Serial Clock Period, t
Data In Setup Time to SCL High, t
Data Out Stable after SCL Low, t
f
OL
2
1
2
3
2.5 µs See Figure 1
50 ns See Figure 1
0 ns See Figure 1
0.4 V IOL = 3 mA
= 5 V
OH
250 ns CL = 400 pF, IO = 3 mA
0.8 V I
OUT
= 4 mA
AD7416/AD7417/AD7418
SDA Low Setup Time to SCL Low
(Start Condition), t
4
50 ns See Figure 1
SDA High Hold Time after SCL High
(Stop Condition), t
SDA and SCL Fall Time, t
NOTES
1
For VDD = 2.7 V to 3 V, T
2
Sample tested during initial release and after any redesign or process change that may affect this parameter.
Specifications subject to change without notice.
5
6
max = +85°C and accuracy = ±3°C.
A
50 ns See Figure 1
90 ns See Figure 1
1
1
t
1
SCL
SDA
DATA IN
SDA
DATA OUT
t
4
t
2
Figure 1. Diagram for Serial Bus Timing
REV. B –3–
t
5
t
3
t
6
Page 4
AD7416/AD7417/AD7418
AD7417 PIN FUNCTION DESCRIPTION
Pin No. Mnemonic Description
1, 16 NC No Connection. Do not connect anything to this pin.
2 SDA Digital I/O. Serial Bus Bidirectional Data. Push-pull output.
3 SCL Digital Input. Serial Bus Clock.
4 OTI This is a logic output. The Over Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (temperature sensor) is greater than an 8-bit word in the Over Temperature Register (OTR).
The signal is reset at the end of a serial read operation. Open-drain output.
5 REF
IN
6 GND Ground Reference for Track/Hold, Comparator and Capacitor DAC, and Digital Circuitry.
7–10 A
IN1
to A
11 A2 Digital Input. The highest programmable bit of the Serial Bus Address.
12 A1 Digital Input. The middle programmable bit of the Serial Bus Address.
13 A0 Digital Input. The lowest programmable bit of the Serial Bus Address.
14 V
DD
15 CONVST Logic Input Signal. Convert Start Signal. The rising edge of this signal fully powers up the part. The
Reference Input. An external 2.5 V reference can be connected to the AD7417 at this pin. To enable
the on-chip reference the REF
pin should be tied to GND. If an external reference is connected to
IN
the AD7417, the internal reference will shut down.
Analog Input Channels. The AD7417 has four analog input channels. The input channels are single-
IN4
ended with respect to GND. The input channels can convert voltage signals in the range 0 V to V
A channel is selected by writing to the configuration register of the AD7417. (See Control Byte section.)
Positive Supply Voltage, +2.7 V to +5.5 V.
power-up time for the part is 4 µs. If the CONVST pulse is greater than 4 µs, the falling edge of
CONVST places the track/hold mode into hold mode and initiates a conversion. If the pulse is less
than 4 µs, an internal timer ensures that the track/hold does not go into hold and conversion is not
initiated until the power-up time has elapsed. The track/hold goes into track mode again at the end of
conversion. (See Operating Mode section.)
REF
.
AD7417 PIN CONFIGURATION
SOIC/TSSOP
1
NC
2
SDA
3
SCL
4
OTI
5
REF
IN
6
GND
7
A
IN1
8
A
IN2
NC = NO CONNECT
AD7417
TOP VIEW
(Not to Scale)
16
15
14
13
12
11
10
9
NC
CONVST
V
DD
A0
A1
A2
A
IN4
A
IN3
–4–
REV. B
Page 5
AD7416/AD7417/AD7418
AD7416 PIN FUNCTION DESCRIPTION
Pin No. Mnemonic Description
1 SDA Digital I/O. Serial Bus Bidirectional Data. Push-pull output.
2 SCL Digital Input. Serial Bus Clock.
3 OTI This is a logic output. The Over-Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Over-Temperature Register
(OTR). The signal is reset at the end of a serial read operation. Open-drain output.
4 GND Ground reference for track/hold, comparator and capacitor DAC, and digital circuitry.
5 A2 Digital Input. The highest programmable bit of the Serial Bus Address.
6 A1 Digital Input. The middle programmable bit of the Serial Bus Address.
7 A0 Digital Input. The lowest programmable bit of the Serial Bus Address.
8VDDPositive Supply Voltage, +2.7 V to +5.5 V.
AD7418 PIN FUNCTION DESCRIPTION
Pin No. Mnemonic Description
1 SDA Digital I/O. Serial Bus Bidirectional Data. Push-pull output.
2 SCL Digital Input. Serial Bus Clock.
3 OTI This is a logic output. The Over-Temperature Indicator (OTI) is set if the result of a conversion on
Channel 0 (Temperature Sensor) is greater that an 8-bit word in the Over-Temperature Register
(OTR). The signal is reset at the end of a serial read operation. Open-drain output.
4 GND Ground reference for track/hold, comparator and capacitor DAC, and digital circuitry.
5A
6 REF
7V
IN
IN
DD
8 CONVST Logic Input Signal. Convert Start Signal. The rising edge of this signal fully powers up the part.
Analog Input Channel. The input channel is single-ended with respect to GND. The input channel
can convert voltage signals in the range 0 V to V
. The analog input channel is selected by writing
REF
to the configuration register of the AD7418 and choosing Channel 4. (See Control Byte section.)
Reference Input. An external 2.5 V reference can be connected to the AD7418 at this pin. To en-
able the on-chip reference the REF
pin should be tied to GND. If an external reference is con-
IN
nected to the AD7418, the internal reference will shut down.
Positive Supply Voltage, +2.7 V to +5.5 V.
The power-up time for the part is 4 µs. If the CONVST pulse is greater than 4 µs, the falling edge
of CONVST places the track/hold mode into hold mode and initiates a conversion. If the pulse is
less than 4 µs, an internal timer ensures that the track/hold does not go into hold and conversion is
not initiated until the power-up time has elapsed. The track/hold goes into track mode again at the
end of conversion. (See Operating Mode section.)
REV. B
AD7416 PIN CONFIGURATION
SOIC/SOIC
SDA
SCL
OTI
GND
1
2
AD7416
TOP VIEW
3
(Not to Scale)
4
8
V
DD
7
A0
6
A1
5
A2
–5–
AD7418 PIN CONFIGURATION
SOIC/SOIC
SDA
SCL
OTI
GND
1
2
AD7418
TOP VIEW
3
(Not to Scale)
4
8
CONVST
7
V
6
REF
5
A
DD
IN
IN
Page 6
AD7416/AD7417/AD7418
WARNING!
ESD SENSITIVE DEVICE
ABSOLUTE MAXIMUM RATINGS
(T
= +25°C unless otherwise noted)
A
1
VDD to AGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3␣ V to +7␣ V
V
to DGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3␣ V to +7␣ V
DD
Analog Input Voltage to AGND
to A
A
IN1
Reference Input Voltage to AGND
Digital Input Voltage to DGND . . . . . . –0.3 V to V
Digital Output Voltage to DGND . . . . . –0.3 V to V
. . . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V
IN4
2
. . . –0.3 V to V
DD
DD
DD
+ 0.3␣ V
+ 0.3 V
+ 0.3 V
Operating Temperature Range
A Version . . . . . . . . . . . . . . . . . . . . . . . . . .–55°C to +125°C
B Version . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . +150°C
TSSOP, Power Dissipation . . . . . . . . . . . . . . . . . . . . 450 mW
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 120°C/W
θ
JA
Lead Temperature, Soldering . . . . . . . . . . . . . . . . . +260°C
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
16-Lead SOIC Package, Power Dissipation . . . . . . . . 450 mW
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 100°C/W
θ
JA
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
8-Lead SOIC Package, Power Dissipation . . . . . . . . . 450 mW
θ
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 157°C/W
JA
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
µSOIC Package, Power Dissipation . . . . . . . . . . . . . . 450 mW
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 206°C/W
θ
JA
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
2
If the Reference Input Voltage is likely to exceed VDD by more than 0.3 V (e.g.,
during power-up) and the reference is capable of supplying 30 mA or more, it is
recommended to use a clamping diode between the REFIN pin and VDD pin. The
diagram below shows how the diode should be connected.
REF
IN
BAT81
AD7417
V
DD
ORDERING GUIDE
Temperature Temperature Package Branding Package
Model Range Error @ +25ⴗC Description Information Options
AD7416AR –55°C to +125°C ±2°C 8-Lead Narrow Body (SOIC) SO-8
AD7416ARM –55°C to +125°C ±2°C 8-Lead µSOIC C6A RM-8
AD7417AR –55°C to +125°C ±2°C 16-Lead Narrow Body (SOIC) R-16A
AD7417ARU –55°C to +125°C ±2°C 16-Lead (TSSOP) RU-16
AD7417BR –40°C to +85°C ±1°C 16-Lead Narrow Body (SOIC) R-16A
AD7418AR –55°C to +125°C ±2°C 8-Lead Narrow Body (SOIC) SO-8
AD7418ARM –55°C to +125°C ±2°C 8-Lead µSOIC C7A RM-8
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD7416/AD7417/AD7418 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore,
proper ESD precautions are recommended to avoid performance degradation or loss of functionality .
–6–
REV. B
Page 7
AD7416/AD7417/AD7418
(continued from page 1)
An I2C-compatible serial interface allows the AD7416/AD7417/
AD7418 registers to be written to and read back. The 3 LSBs
of the AD7416/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 µSOIC packages.
PRODUCT HIGHLIGHTS
1. The AD7416/AD7417/AD7418 have an on-chip temperature sensor that allows an accurate measurement of the am-
bient temperature (±1°C @ +25°C, ±2°C over temperature)
to be made. The measurable temperature range is –55°C to
+125°C. An over-temperature indicator is implemented by
carrying out a digital comparison of the ADC code for
Channel 0 (temperature sensor) with the contents of the onchip over-temperature register.
2. The AD7417 offers a space saving 10-bit A/D solution with
four external voltage input channels, an on-chip temperature
sensor, an on-chip reference and clock oscillator.
3. The automatic power-down feature enables the AD7416/
AD7417/AD7418 to achieve superior power performance.
At slower throughput rates the part can be programmed to
operate in a low power shutdown mode allowing further
savings in power consumption.
TERMINOLOGY
Relative Accuracy
Relative accuracy or endpoint nonlinearity is the maximum
deviation from a straight line passing through the endpoints of
the ADC transfer function.
Differential Nonlinearity
This is the difference between the measured and the ideal
1␣ LSB change between any two adjacent codes in the ADC.
Offset Error
This is the deviation of the first code transition (0000 . . . 000)
to (0000 ...001) from the ideal, i.e., GND + 1 LSB.
Offset Error Match
This is the difference in Offset Error between any two channels.
Gain Error
This is the deviation of the last code transition (1111 . . . 110)
to (1111 ...111) from the ideal, i.e., VREF – 1 LSB, after the
offset error has been adjusted out.
Gain Error Match
This is the difference in gain error between any two channels.
Track/Hold Acquisition Time
Track/hold acquisition time is the time required for the output
of the track/hold amplifier to reach its final value, within ±1/2
LSB, after the end of conversion (the point at which the track/
hold returns to track mode). It also applies to situations where a
change in the selected input channel takes place or where there
is a step input change on the input voltage applied to the selected A
input of the AD7417 or AD7418. It means that the
IN
user must wait for the duration of the track/hold acquisition
time after the end of conversion or after a channel change/step
input change to A
before starting another conversion, to en-
IN
sure that the part operates to specification.
REV. B
–7–
Page 8
AD7416/AD7417/AD7418
CIRCUIT INFORMATION
The AD7417 and AD7418 are single- and four-channel, 15 µs
conversion time, 10-bit A/D converters with on-chip temperature sensor, reference and serial interface logic functions on a
single chip. The AD7416 has no analog input channel and is
intended for temperature measurement only. The A/D converter
section consists of a conventional successive-approximation
converter based around a capacitor DAC. The AD7416, AD7417
and AD7418 are capable of running on a 2.7 V to 5.5 V power
supply and the AD7417 and AD7418 accept an analog input
range of 0 V to +VREF. The on-chip temperature sensor allows
an accurate measurement of the ambient device temperature to
be made. The working measurement range of the temperature
sensor is –55°C to +125°C. The parts require a +2.5 V refer-
ence 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 µs
after the read or write operation is complete and a conversion is
then initiated. The result of the conversion is available either
15 µs or 30 µs later, depending on whether an analog input
channel or the temperature sensor is selected. The track/hold
acquisition time of the AD7417/AD7418 is 400 ns.
A temperature measurement is made by selecting the Channel 0
of the on-chip MUX and carrying out a conversion on this
channel. A conversion on Channel 0 takes 30 µs to complete.
Temperature measurement is explained in the Temperature
Measurement section of this data sheet.
The on-chip reference is not available to the user, but REF
IN
can be overdriven by an external reference source (+2.5 V only).
The effect of reference tolerances on temperature measurements
is discussed in the Reference section of the data sheet.
All unused analog inputs should be tied to a voltage within the
nominal analog input range to avoid noise pickup. For minimum power consumption, the unused analog inputs should be
tied to GND.
TYPICAL CONNECTION DIAGRAM
Figure 2 shows a typical connection diagram for the AD7417.
Using the A0, A1 and A2 pins allows the user to select from up
to eight AD7417s on the same serial bus, if desired. An external
2.5 V reference can be connected at the REF
pin. If an exter-
IN
nal reference is used, a 10 µF capacitor should be connected
between REF
2
I
C-compatible interface. For applications where power con-
and GND. SDA and SCL form the two-wire
IN
sumption is of concern, the automatic power-down at the end of
a conversion should be used to improve power performance. See
Operating Modes section of the data sheet.
SUPPLY
+2.7V TO
+5.5V
0V TO +2.5V
OPTIONAL
EXTERNAL
REFERENCE
INPUT
AD780/
REF-192
AIN1
AIN2
AIN3
AIN4
GND
0.1mF10mF
AD7417
V
REF
DD
CONVST
IN
TWO-WIRE
SERIAL
INTERFACE
SCL
SDA
OTI
A0
A1
A2
10mF FOR
EXTERNAL
REFERENCE
mC/mP
Figure 2. Typical Connection Diagram
ANALOG INPUTS
Figure 3 shows an equivalent circuit of the analog input structure of the AD7417 and AD7418. The two diodes, D1 and D2,
provide ESD protection for the analog inputs. Care must be
taken to ensure that the analog input signal never exceeds the
supply rails by more than 200 mV. This will cause these diodes
to become forward-biased and start conducting current into the
substrate. The maximum current these diodes can conduct
without causing irreversible damage to the part, is 20 mA. The
capacitor C2 in Figure 3 is typically about 4 pF and can primarily be attributed to pin capacitance. The resistor R1 is a
lumped component made up of the on resistance of a multi-
kΩ
plexer and a switch. This resistor is typically about 1
. The
capacitor C1 is the ADC sampling capacitor and has a capacitance of 3 pF.
V
DD
D1
A
IN
4pF
C2
D2
R1
1kV
CONVERT PHASE – SWITCH OPEN
TRACK PHASE – SWITCH CLOSED
C1
3pF
V
BALANCE
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
pin to analog ground. This causes SW1—(see Figure
IN
4) to open and the reference amplifier to power up during a
conversion. Therefore the on-chip reference is not available
externally. An external 2.5 V reference can be connected to the
pin. This has the effect of shutting down the on-chip
REF
IN
reference circuitry.
–8–
REV. B
Page 9
AD7416/AD7417/AD7418
1.2V
REF
IN
1.2V
SW1
+
26kV
24kV
2.5V
EXTERNAL
REFERENCE
DETECT
+
BUFFER
Figure 4. On-Chip Reference
INTERNAL REGISTER STRUCTURE
The AD7417/AD7418 has seven internal registers, as shown in
Figure 5. Six of these are data registers and one is an address
pointer register. The AD7416 has five internal registers (the
ADC and Config2 registers are not applicable to the AD7416).
TEMPERATURE
VALUE
REGISTER
(READ-ONLY
ADDRESS 00H)
CONFIGURATION
REGISTER
(READ/WRITE
ADDRESS 01H)
T
SET-POINT
HYST
REGISTER
(READ/WRITE
ADDRESS 02H)
SET-POINT
T
OTI
REGISTER
(READ/WRITE
ADDRESS 03H)
ADDRESS POINTER
REGISTER
(SELECTS DATA REGISTER
FOR READ/WRITE)
ADDRESS
INTERFACE
REGISTER
(READ ONLY
ADDRESS 04H)
CONFIG 2
REGISTER
(READ/WRITE
ADDRESS 05H)
SERIAL
BUS
ADC
DATA
SDA
SCL
Figure 5. AD7417/AD7418 Register Structure
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.
Table II. Register Addresses
P2 P1 P0 Registers
000Temperature Value (Read Only)
001Config Register (Read/Write)
010T
011T
(Read/Write)
HYST
OTI
1 0 0 ADC (AD7417/AD7418 Only)
101Config2 (AD7417/AD7418 Only)
TEMPERATURE VALUE REGISTER (ADDRESS 00H)
The temperature value register is a 16-bit, read-only register
whose 10 MSBs store the temperature reading from the ADC in
10-bit twos complement format. Bits 5 to 0 are unused.
Table III. Temperature Value Register
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6
MSB B8 B7 B6 B5 B4 B3 B2 B1 LSB
The temperature data format is shown in Table IV. This shows
the full theoretical range of the ADC from –128°C to +127°C,
but in practice the temperature measurement range is limited to
the operating temperature range of the device.
Table IV. Temperature Data Format
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 outlined in Table VI. These bits should always be 0,0,0 for the
AD7416. Bits D4 and D3 are used to set the length of the fault
queue. D2 sets the sense of the OTI output. D1 selects comparator or interrupt mode of operation, and D0 selects shutdown mode.
Table I. Address Pointer Register
P7* P6* P5* P4* P3* P2 P1 P0
00000 Register Select
*P3 to P7 must be set to 0.
REV. B
Table V. Configuration Register
D7 D6 D5 D4 D3 D2 D1 D0
Channel Fault OTI Cmp/ ShutSelection Queue Polarity Int down
–9–
Page 10
AD7416/AD7417/AD7418
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.
Table VI. Channel Selection
D7 D6 D5 Channel Selection
0 0 0 Temperature Sensor (All Parts)
0 0 1 AIN1 (AD7417 Only)
0 1 0 AIN2 (AD7417 Only)
0 1 1 AIN3 (AD7417 Only)
1 0 0 AIN4 (AD7417) and AIN (AD7418)
Table VII. Fault Queue Settings
D4 D3 Number of Faults
0 0 1 (Power Up Default)
012
104
116
111...111
111...110
111...000
011...111
ADC CODE
000...010
000...001
000...000
0V 1/2LSB +V
1LSB = V
REF
ANALOG INPUT
REF
–1LSB
/1024
Figure 6.
CONFIG2 REGISTER (ADDRESS 05H)
A second configuration register is included in the AD7417/
AD7418 for the functionality of the CONVST pin. It is an 8 bit
register with bits D5 to D0 being left at 0. Bit D7 determines
whether the AD7417/AD7418 should be operated in its default
mode (D7 = 0), performing conversions every 355 µs or in
CONVST pin mode (D7 = 1), where conversions will start only
when the CONVST pin is used. Bit 6 contains the Test 1 bit.
When this bit is 0 the I
2
C filters are enabled (default). A 1
disables the filters.
Table X.
T
SETPOINT REGISTER (ADDRESS 02H)
HYST
The T
whose 9 MSBs store the T
Setpoint Register is a 16-bit, read/write register
HYST
setpoint in twos complement
HYST
format equivalent to the 9 MSBs of the temperature value register. Bits 6 to 0 are unused.
T
SETPOINT REGISTER (ADDRESS 03H)
OTI
The T
9 MSBs store the T
Setpoint Register is a 16-bit, read/write register whose
OTI
setpoint in twos complement format
OTI
equivalent to the 9 MSBs of the temperature value register. Bits
6 to 0 are unused.
Table VIII. Setpoint Registers
D15 D14 D13 D12 D11 D10 D9 D8 D7
MSBB7B6B5B4B3B2B1LSB
ADC VALUE REGISTER (ADDRESS 04H)
The ADC value register is a 16-bit, read only register whose
10 MSBs store the value produced by the ADC in binary format. Bits 5 to 0 are unused. Table IX shows the ADC value
register with 10 MSBs containing the ADC conversion request.
Table IX.
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6
MSBB8B7B6B5B4B3B2B1LSB
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.
D7 D6 D5 D4 D3 D2 D1 D0
Conversion Mode Test 1 000000
SERIAL BUS INTERFACE
Control of the AD7416/AD7417/AD7418 is carried out via the
2
I
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 I2C-compatible devices, the AD7416/AD7417/AD7418
have a 7-bit serial address. The four MSBs of this address for
the AD7416 are set to 1001, the AD7417 are 0101, while the
three LSBs can be set by the user by connecting the A2 to A0
pins to either +V
or GND. By giving them different addresses,
S
up to eight AD7416/AD7417s can be connected to a single
serial bus, or the addresses can be set to avoid conflicts with
other devices on the bus. The four MSBs of this address for the
AD7418 are 0101, while the three LSBs are all set to zero.
The serial bus protocol operates as follows:
1. The master initiates data transfer by establishing a START
condition, defined as a high-to-low transition on the serial
data line SDA while the serial clock line SCL remains high.
This indicates that an address/data stream will follow. All
slave peripherals connected to the serial bus respond to the
START condition, and shift in the next eight bits, consisting
of a 7-bit address (MSB first) plus a R/W bit, which determines the direction of the data transfer, i.e., whether data
will be written to or read from the slave device.
The peripheral whose address corresponds to the transmitted
address responds by pulling the data line low during the low
period before the ninth clock pulse, known as the Acknowledge Bit. All other devices on the bus now remain idle while
–10–
REV. B
Page 11
AD7416/AD7417/AD7418
the selected device waits for data to be read from or written
to it. If the R/W bit is a 0 then the master will write to the
slave device. If the R/W bit is a 1 the master will read from
the slave device.
2. Data is sent over the serial bus in sequences of nine clock
pulses, eight bits of data followed by an Acknowledge Bit
from the receiver of data. Transitions on the data line must
occur during the low period of the clock signal and remain
stable during the high period, as a low-to-high transition
when the clock is high may be interpreted as a STOP signal.
3. When all data bytes have been read or written, stop conditions are established. In WRITE mode, the master will pull
the data line high during the 10th clock pulse to assert a
STOP condition. In READ mode, the master device will pull
the data line high during the low period before the 9th clock
pulse. This is known as No Acknowledge. The master will
then take the data line low during the low period before the
10th clock pulse, then high during the 10th clock pulse to
assert a STOP condition.
Any number of bytes of data may be transferred over the serial
bus in one operation, but it is not possible to mix read and write
in one operation, because the type of operation is determined at
the beginning and cannot subsequently be changed without
starting a new operation.
WRITING TO THE AD7416/AD7417/AD7418
Depending on the register being written to, there are three different writes for the AD7416/AD7417/AD7418.
1. Writing to the Address Pointer Register for a subsequent
read.
In order to read data from a particular register, the Address
Pointer Register must contain the address of that register. If
it does not, the correct address must be written to the Address Pointer register by performing a single-byte write
operation, as shown in Figure 7. The write operation consists
of the serial bus address followed by the address pointer byte.
No data is written to any of the data registers.
2. Writing a single byte of data to the Configuration Registers
or T
, T
OTI
Registers.
HYST
The Configuration Register is an 8-bit register, so only one
byte of data can be written to it. If only 8-bit temperature
comparisons are required, the temperature LSB can be ignored in T
to the T
OTI
and T
OTI
and T
, and only eight bits need be written
HYST
registers.
HYST
Writing a single byte of data to one of these registers consists
of the serial bus address, the data register address, written to
the Address Pointer Register, followed by the data byte,
written to the selected data register. This is illustrated in
Figure 8.
SCL
SDA
START BY
MASTER
191
1
001A2
FRAME 1
SERIAL BUS ADDRESS BYTE
A0
A1
R/W
ACK. BY
AD7416
P6
P7
P5 P4
ADDRESS POINTER REGISTER BYTE
P3
FRAME 2
P1
P2
P0
9
ACK. BY
AD7416
STOP BY
MASTER
Figure 7. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation
SCL
SDA
START BY
MASTER
19
001A2 A1 A0 P7 P6 P5
1
FRAME 1
SERIAL BUS ADDRESS BYTE
SCL (CONTINUED)
SDA (CONTINUED)
R/W
ACK. BY
AD7416
1
P3 P2 P1 P0
P4
ADDRESS POINTER REGISTER BYTE
19
D6 D5
D7
D4
FRAME 2
D3 D2 D1 D0
FRAME 3
DATA BYTE
ACK. BY
AD7416
9
ACK. BY
AD7416
STOP BY
MASTER
Figure 8. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register
REV. B
–11–
Page 12
AD7416/AD7417/AD7418
3. Writing two bytes of data to the T
If 9-bit resolution is required for the temperature setpoints,
then two bytes of data must be written to the T
T
registers. This consists of the serial bus address, the
HYST
register address, written to the address pointer register, followed by two data bytes written to the selected data register.
This is illustrated in Figure 9.
OTI
or T
HYST
Register.
and
OTI
READING DATA FROM THE AD7416/AD7417/AD7418
Reading data from the AD7416/AD7417/AD7418 is a one or
two byte operation. Reading back the contents of the Configuration Register is a single byte read operation, as shown in Figure
10, the register address previously having been set by a singlebyte write operation to the address pointer register.
Reading data from the temperature value, T
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.
191
SCL
SDA 0 0
START BY
MASTER
SCL
(CONTINUED)
SDA
(CONTINUED)
1
SERIAL BUS ADDRESS BYTE
19
D15 D14
A2
1
FRAME 1
D12 D11
D13
MOST SIGNIFICANT DATA BYTE
FRAME 3
A0
A1
D10
D9
R/W
ACK. BY
AD7416
D8
ACK. BY
AD7416
P6
P7
19
D7 D6
STOP BY
MASTER
P4 P3 P2 P1 P0
P5
ADDRESS POINTER REGISTER BYTE
FRAME 2
D4 D3
D5
LEAST SIGNIFICANT DATA BYTE
FRAME 4
Figure 9. Writing to the Address Pointer Register Followed by a Two Bytes of Data to the T
D2
D1
ACK. BY
AD7416
D0
or T
OTI
9
ACK. BY
AD7416
OTI
HYST
, or T
HYST
STOP BY
MASTER
Register
regis-
SCL
SDA
START BY
MASTER
SCL
SDA
START BY
MASTER
191 9
0
FRAME 1
SERIAL BUS ADDRESS BYTE
A0A1A2101
R/W
ACK. BY
AD7416
D7 D6 D5 D4 D3 D2 D1 D0
NO ACK. BY
SINGLE DATA BYTE FROM AD7416
FRAME 2
MASTER
STOP BY
MASTER
Figure 10. Reading a Single Byte of Data from the Configuration Register
19
0 0 1 A2 A1 A0 D15 D14 D13
1
FRAME 1
SERIAL BUS ADDRESS BYTE
SCL (CONTINUED)
SDA (CONTINUED)
R/W
ACK. BY
AD7416
Figure 11. Reading Two Bytes of Data from T
1
D10 D11 D9 D8
D12
MOST SIGNIFICANT DATA BYTE FROM AD7416
19
D6 D5
D7
LEAST SIGNIFICANT DATA BYTE FROM AD7416
D4
OTI
FRAME 2
D3 D2 D1 D0
FRAME 3
or T
HYST
Register
NO ACK. BY
MASTER
9
ACK. BY
MASTER
STOP BY
MASTER
–12–
REV. B
Page 13
AD7416/AD7417/AD7418
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
falls below T
HYST
, and remains active until the temperature
OTI
. This mode allows the AD7416/AD7417/
AD7418 to be used as a thermostat, for example to control the
operation of a cooling fan.
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 INDEFINITLY, 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 temperature excursion has occurred. OTI is an open-drain output
that can be programmed to be active low by setting Bit D2 of
the Configuration Register to 0, or active high by setting Bit D2
of the Configuration Register to 1.
In the Interrupt mode (D1 = 1), the OTI output becomes active
when the temperature exceeds T
the temperature falls below T
HYST
, and remains active even if
OTI
, until it is reset by a read opera-
tion. Once OTI has become active by the temperature exceeding
, then been reset, it will remain inactive even if the tempera-
T
OTI
ture remains, or subsequently rises again, above T
become active again until the temperature falls below T
. It will not
OTI
HYST
. It
will then remain active until reset by a read operation. Once
OTI has become active by the temperature falling below T
HYST
,
then been reset, it will remain inactive even if the temperature
remains, or subsequently falls again, below T
HYST
.
OTI is also reset when the AD7416/AD7417/AD7418 is placed
in shutdown mode, by setting bit D0 of the Configuration Register to 1.
The OTI output requires an external pull-up resistor. This can
be connected to a voltage different from +V
(for example, to
S
allow interfacing between 5 V and 3.3 V systems) provided that
the maximum voltage rating of the OTI output is not exceeded.
The value of the pull-up resistor depends on the application, but
should be as large as possible to avoid excessive sink currents at
the OTI output, which can heat the chip and affect the temperature reading. The maximum value of pull-up resistor that will
meet the output high current specification of the OTI output is
30 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.
FAULT QUEUE
To avoid false triggering of the AD7416/AD7417/AD7418 in
noisy environments, a fault queue counter is provided, which
can be programmed by Bits D3 and D4 of the Configuration
Register (see Table V) to count 1, 2, 4 or 6 fault events before
OTI becomes active. In order to trigger OTI, the faults must
occur consecutively. For example, if the fault queue is set to 4,
then four consecutive temperature measurements greater than
(or less than T
T
OTI
) must occur. Any reading that breaks
HYST
the sequence will reset the fault queue counter, so if there are
three readings greater than T
T
, the fault queue counter will be reset without triggering OTI.
OTI
followed by a reading less than
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
= 80°C
OTI
T
= 75°C
HYST
OTI Active LOW
Fault Queue = 1
These default settings allow the AD7416/AD7417/AD7418 to
be used as a stand-alone thermostat without any connection to a
serial bus.
OPERATING MODES
The AD7416/AD7417/AD7418 has two possible modes of
operation depending on the value of D0 in the Configuration
Register.
Mode 1
Normal operation of the AD7416/AD7417/AD7418 occurs when
D0 = 0. In this active mode, a conversion takes place every
400 µs. Once the conversion has taken place, the part partially
powers down, consuming typically 350 µA of current until the
next conversion occurs.
Two situations can arise in this mode on the request of a temperature read. If a read occurs during a conversion, the conversion aborts and a new one starts on the Stop/Repeat start
condition. The temperature value that is read is that of the
previous completed conversion. The next conversion will typi-
cally occur 400 µs after the new conversion has begun.
If a read is called between conversions, a conversion is initiated
on the stop/repeat start condition. After this conversion, the part
returns to performing a conversion every 400 µs.
With a V
= 3 V, for each 400 µs cycle, the AD7416 spends
DD
40 µs (or 10% of the time) in conversion mode. It spends 360 µs
(or 90% of time) in partial power-down mode. Thus the average
power dissipated by the AD7416/AD7417/AD7418 is:
3 mW × 0.1 + 1 mW × 0.9 = 1.2 mW
Mode 2
For applications where temperature measurements are required
at a slower rate e.g., every second, power consumption of the
part can be reduced by writing to the part to go to a full powerdown 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
REV. B
–13–
Page 14
AD7416/AD7417/AD7418
part. The part then performs a conversion and is returned to
power-down. The temperature value can be read in the full
power-down because the I
2
C bus is continuously active.
The power dissipation in this mode depends on the rate at
which reads take place. Taking the requirements for a temperature measurement every 100 ms as an example, the optimum
power dissipation is achieved by placing the part in full 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:
3 mW × 0.004 + 60 nW × 0.9996 = 1.2
µ
W
The fastest throughput rate at which the AD7416/AD7417/
AD7418 can be operated is 2.5 kHz (i.e., a read every 400 µs
conversion period). Since T
the read time with the I
and T
OTI
2
C operating at 100 kbit/s would be
are two byte reads,
HYST
270 µs. If temperature reads are called too often, reads will
overlap with conversions, aborting them continuously, which
results in invalid readings.
CONVERT START MODE
The AD7417/AD7418 has an extra mode, set by writing to the
MSB of the Config2 Register.
CONVST Mode
By setting the CONVST mode bit to 1, conversions are initiated
only by using the CONVST pin. When the AD7417/AD7418 is
in this CONVST mode, there are two possible methods of operation, depending on the status of the CONVST line at the end
of conversion.
If the CONVST line is high at the end of a conversion, the
AD7417/AD7418 remains powered up at the end of a conversion and the next conversion is initiated and the track/hold goes
into hold mode on the next falling edge of CONVST. The part
never powers down provided the D0 bit of the configuration
register remains at 0. In this method of operation, CONVST is
normally high with a low-going pulse controlling the track/hold
and conversion starts.
The second method is where the CONVST input is low at the
end of conversion. When this happens, the part automatically
enters its power-down mode at the end of conversion. The next
rising edge of CONVST starts the power-up time. This powerup time is 4 µs. If the CONVST high time is longer than 4 µs,
a conversion is initiated on the falling edge of CONVST and
the track/hold also enters its hold mode at this time. If the
CONVST high time is less than 4 µs, an internal timer, initiated
by the rising edge of CONVST holds of the track/hold and the
initiation of conversion until timer times out (4 µs after the
rising edge of CONVST, which corresponds with the power-up
time). 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. When performing temperature conversions,
a minimum of 40 µs should be left between any two CONVST
pulses to allow temperature conversions to complete before
starting another.
APPLICATIONS INFORMATION
SUPPLY DECOUPLING
The AD7416/AD7417/AD7418 should be decoupled with a
0.1 µF ceramic capacitor between +V
and GND. This is
S
particularly important if the part is mounted remote from the
power supply.
MOUNTING THE AD7416
The AD7416/AD7417/AD7418 can be used for surface or airtemperature sensing applications. If the device is cemented to a
surface with thermally conductive adhesive, the die temperature
will be within about 0.2°C of the surface temperature, thanks to
the device’s low power consumption. Care should be taken to
insulate the back and leads of the device from the air, if the
ambient air temperature is different from the surface temperature being measured.
The ground pin provides the best thermal path to the die, so the
temperature of the die will be close to that of the printed circuit
ground track. Care should be taken to ensure that this is in good
thermal contact with the surface being measured.
As with any IC, the AD7416/AD7417/AD7418 and its associated wiring and circuits must be kept free from moisture to
prevent leakage and corrosion, particularly in cold conditions
where condensation is more likely to occur. Water resistant
varnishes and conformal coatings can be used for protection.
The small size of the AD7416 package allows it to be mounted
inside sealed metal probes, which provide a safe environment for
the device.
FAN CONTROLLER
Figure 13 shows a simple fan controller that will switch on a
cooling fan when the temperature exceeds 80°C, and switch it
off again when the temperature falls below 75°C. The AD7416
can be used stand-alone in this application, or with a serial bus
interface if different trip temperatures are required. If the AD7416
is used with a bus interface, the sense of OTI can be set to active high, Q1 and R1 can be omitted, and OTI connected directly to the gate of Q2, with R2 as the pull-up resistor.
+12V
+V
S
3V TO 5.5V
Q2
LOGIC LEVEL
MOSFET RATED
TO SUIT FAN
CURRENT
AD7416
R1
10kV
R2
10kV
Q1
2N3904
OR SIMILAR
Figure 13. AD7416 Used as a Fan Controller
–14–
REV. B
Page 15
AD7416/AD7417/AD7418
THERMOSTAT
Figure 14 shows the AD7416 used as a thermostat. The heater
will be switched on when the temperature falls below T
and switched off again when the temperature rises above T
HYST
OS
,
.
For this application, the OTI output should be programmed
active low, and for comparator mode.
+V
S
3V TO 5.5V
AD7416
R1
10kV
RELAY
Q1
2N3904
OR SIMILAR
D1
1N4001
HEATER
RLA1
HEATER
SUPPLY
Figure 14. AD7416 Used as a Thermostat
+V
S
3V TO 5.5V
R1
10kV
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 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
Figure 15. Multiple Connection of AD7416s to a Single Serial Bus
AD7416
AD7416
SUPER I/O CHIP
PROCESSOR
REV. B
–15–
Page 16
AD7416/AD7417/AD7418
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
0.1574 (4.00)
0.1497 (3.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
0.1574 (4.00)
0.1497 (3.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
16-Lead Narrow Body (SOIC)
(R-16A)
0.3937 (10.00)
0.3859 (9.80)
16 9
PIN 1
0.0500
0.0192 (0.49)
(1.27)
0.0138 (0.35)
BSC
0.2440 (6.20)
81
0.2284 (5.80)
0.0688 (1.75)
0.0532 (1.35)
0.0099 (0.25)
0.0075 (0.19)
8-Lead Narrow Body (SOIC)
(SO-8)
0.1968 (5.00)
0.1890 (4.80)
8
5
0.2440 (6.20)
41
0.2284 (5.80)
PIN 1
0.0500
(1.27)
BSC
0.0688 (1.75)
0.0532 (1.35)
0.0192 (0.49)
0.0138 (0.35)
0.0098 (0.25)
0.0075 (0.19)
8°
0°
0.0196 (0.50)
0.0099 (0.25)
8°
0°
0.0500 (1.27)
0.0160 (0.41)
0.0196 (0.50)
0.0099 (0.25)
0.0500 (1.27)
0.0160 (0.41)
x 45°
x 45°
16-Lead Thin Shrink Small Outline Package
(TSSOP) (RU-16)
0.201 (5.10)
0.193 (4.90)
16 9
0.177 (4.50)
0.006 (0.15)
0.002 (0.05)
SEATING
PLANE
0.169 (4.30)
1
PIN 1
0.0256
(0.65)
BSC
0.0118 (0.30)
0.0075 (0.19)
8
0.256 (6.50)
0.246 (6.25)
0.0433
(1.10)
MAX
0.0079 (0.20)
0.0035 (0.090)
8°
0°
0.028 (0.70)
0.020 (0.50)
8-Lead SOIC Package
(RM-8)
0.122 (3.10)
0.114 (2.90)
0.122 (3.10)
0.114 (2.90)
0.006 (0.15)
0.002 (0.05)
SEATING
PLANE
85
PIN 1
0.0256 (0.65) BSC
0.120 (3.05)
0.112 (2.84)
0.018 (0.46)
0.008 (0.20)
0.199 (5.05)
0.187 (4.75)
41
0.043 (1.09)
0.037 (0.94)
0.011 (0.28)
0.003 (0.08)
0.120 (3.05)
0.112 (2.84)
338
278
C3449b–0–10/99
0.028 (0.71)
0.016 (0.41)
–16–
PRINTED IN U.S.A.
REV. B
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