FEATURES
10-Bit ADC with 15 s and 30 s Conversion Times
Single and Four Single-Ended Analog Input Channels
On-Chip Temperature Sensor: –40ⴗC to +125ⴗC
On-Chip Track-and-Hold
Overtemperature Indicator
Automatic Power-Down at the End of a Conversion
Wide Operating Supply Range: 2.7 V to 5.5 V
2C®
Compatible Serial Interface
I
Selectable Serial Bus Address Allows Connection of up
to Eight AD7416/AD7417s to a Single Bus
AD7416 Is a Superior Replacement for LM75
APPLICATIONS
Data Acquisition with Ambient Temperature Monitoring
Industrial Process Control
Automotive
Battery-Charging Applications
Personal Computers
GENERAL DESCRIPTION
The AD7417 and AD7418 are 10-bit, 4-channel and singlechannel ADCs with an on-chip temperature sensor that
can operate from a single 2.7 V to 5.5 V power supply. The
devices contain a 15 µs successive approximation converter, a
5-channel multiplexer, a temperature sensor, a clock oscillator, a track-and-hold, and a reference (2.5 V). The AD7416
is a temperature-monitoring only device in an 8-lead package.
The temperature sensor on the parts can be accessed via multiplexer Channel 0. When Channel 0 is selected and a conversion
is initiated, the resulting ADC code at the end of the conversion
gives a measurement of the ambient temperature (±1°C @ 25°C).
On-chip registers can be programmed with high and low temperature limits, and an open-drain overtemperature indicator
(OTI) output is provided, which becomes active when a programmed limit is exceeded.
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)
ADDRESS
REGISTER
A0
A1
A2
A
IN1
A
IN2
A
IN3
A
IN4
NC = NO CONNECT
A
IN1
FUNCTIONAL BLOCK DIAGRAMS
BAND GAP
TEMPERATURE
SENSOR
POINTER
TEMP
SENSOR
MUX
NC NC GND
V
DD
TEMP
SENSOR
MUX
REF
2.5V
SAMPLING
CAPACITOR
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
REF
IN
OVERTEMP REG
CLOCK
V
BALANCE
CONVST
REF
IN
OVERTEMP REG
CLOCK
V
DD
CHARGE
DISTRIBUTION
DAC
CONTROL
LOGIC
+
CHARGE
DISTRIBUTION
DAC
CONTROL
LOGIC
+
COMPARATOR
AD7416
SETPOINT
FAULT
QUEUE
COUNTER
A > B
B
DATA OUT
INTERFACE
AD7417
B
DATA OUT
INTERFACE
A
I2C
A > B
A
I2C
V
DD
OTI
GND
SDA
SCL
OTI
SCL
SDA
A2A1A0
OTI
SCL
SDA
REV. G
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
Resolution1010Bits
Minimum Resolution for Which No
Missing Codes Are Guaranteed1010Bits
Relative Accuracy
Differential Nonlinearity
Gain Error
Gain Error Match
Offset Error
2
2
2
2
2
± 1±1LSB maxThis Specification Is Typical for VDD of
3.6 V to 5.5 V.
± 1±1LSB maxThis Specification Is Typical for VDD of
3.6 V to 5.5 V.
± 3±3LSB maxExternal Reference.
± 10± 10LSB maxInternal Reference.
± 0.6± 0.6LSB maxAD7417 Only.
± 4±4LSB max
Offset Error Match± 0.7± 0.7LSB maxAD7417 Only.
ANALOG INPUTS
Input Voltage RangeV
Input Leakage Current
3
REF
00 V min
± 1±1µA max
V
REF
V max
Input Capacitance1010pF max
TEMPERATURE SENSOR
1
Measurement Error
Ambient Temperature 25°C± 2±1°C max
to T
T
MIN
MAX
± 3±2°C max
Temperature Resolution1/41/4°C/LSB
CONVERSION RATE
Track-and-Hold Acquisition Time
4
400400ns maxSource Impedance < 10 Ω.
Conversion Time
Temperature Sensor3030µs maxTypically 27 µs.
Channels 1 to 41515µs maxTypically 10 µs.
REFERENCE INPUT
REFIN Input Voltage Range
5, 6
6
2.6252.625V max2.5 V + 5%.
2.3752.375V min2.5 V – 5%.
Input Impedance4040kΩ min
Input Capacitance1010pF max
ON-CHIP REFERENCENominal 2.5 V.
Reference Error
Temperature Coefficient
6
6
± 25± 25mV max
8080ppm/°C typ
DIGITAL INPUTS
Input High Voltage, V
Input Low Voltage, V
IL
IH
VDD × 0.7VDD × 0.7V min
VDD × 0.3VDD × 0.3V max
Input Leakage Current11µA max
DIGITAL OUTPUTS
Output Low Voltage, V
OL
0.40.4V maxIOL = 3 mA.
Output High Current11µA maxVOH = 5 V.
POWER REQUIREMENTS
V
DD
5.55.5V maxFor Specified Performance.
2.72.7V min
I
DD
Logic Inputs = 0 V or V
DD.
Normal Operation600600µA max
Power-Down11µA max50 nA Typically.
Auto Power-Down ModeV
= 3 V. See Operating Modes.
DD
10 SPS Throughput Rate66µW typ
1 kSPS Throughput Rate6060µW typ
10 kSPS Throughput Rate600600µW typ
Power-Down33µW maxTypically 0.15 µW.
REV. G–2–
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 –40°C to +125°C. For VDD = 2.7 V, TA = 85°C max
and temperature sensor measurement error = ± 3°C.
2
See Terminology.
3
Refers to the input current when the part is not converting. Primarily due to reverse leakage current in the ESD protection diodes.
4
Sample tested during initial release and after any redesign or process change that may affect this parameter.
5
On-chip reference shuts down when external reference is applied.
6
The accuracy of the temperature sensor is affected by reference tolerance. The relationship between the two is explained in the Temperature Sensor section.
Specifications subject to change without notice.
AD7416–SPECIFICATIONS
(VDD = 2.7 V to 5.5 V, GND = 0 V, REFIN = 2.5 V, unless otherwise noted.)
ParameterMinTypMaxUnitTest Conditions/Comments
TEMPERATURE SENSOR AND ADC
Accuracy± 2.0°CT
± 3.0°CT
= –25°C to +100°C
A
(V
= 3 V min)
DD
= –40°C to +125°C
A
= 3 V min)
(V
DD
1
1
Resolution10Bits
Temperature Conversion Time40µs
Update Rate, t
OTI Delay1 × t
R
R
Supply Current1.0mAI
400µs
6 × t
R
350600µAI
msDepends on Fault Queue Setting
2
C Active
2
C Inactive
0.21.5µAShutdown Mode
T
Default Temperature80°C
OTI
T
Default Temperature75°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
VDD × 0.7VDD + 0.5V
–0.3VDD × 0.3V
+0.005+1.0µAV
–0.005–1.0µAV
20pFAll Digital Inputs
= 5 V
IN
= 0 V
IN
DIGITAL OUTPUTS
Output Low Voltage, V
OL
Output High Current1µAV
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
For VDD = 2.7 V to 3 V, TA max = 85°C and accuracy = ± 3°C.
2
Sample tested during initial release and after any redesign or process change that may affect this parameter.
Specifications subject to change without notice.
5
6
50nsSee Figure 1
300nsSee Figure 1
REV. G
SCL
SDA
DATA IN
SDA
DATA OUT
t
1
t
4
t
2
t
3
t
6
Figure 1. Diagram for Serial Bus Timing
–3–
t
5
Page 4
AD7416/AD7417/AD7418
AD7417 PIN FUNCTION DESCRIPTION
Pin No.MnemonicDescription
1, 16NCNo Connection. Do not connect anything to this pin.
2SDADigital I/O. Serial bus bidirectional data. Push-pull output.
3SCLDigital Input. Serial bus clock.
4OTIThis is a logic output. The overtemperature indicator (OTI) is set if the result of a conversion on
Channel 0 (temperature sensor) is greater than an 8-bit word in the overtemperature register (OTR).
The signal is reset at the end of a serial read operation. Open-drain output.
5REF
IN
6GNDGround reference for track-and-hold, comparator and capacitor DAC, and digital circuitry.
7–10A
IN1
to A
11A2Digital Input. The highest programmable bit of the serial bus address.
12A1Digital Input. The middle programmable bit of the serial bus address.
13A0Digital Input. The lowest programmable bit of the serial bus address.
14V
DD
15CONVSTLogic 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 REFIN pin should be tied to GND. If an external reference is connected to the
AD7417, the internal reference will shut down.
Analog Input Channels. The AD7417 has four analog input channels. The input channels are single-ended
IN4
with respect to GND. The input channels can convert voltage signals in the range 0 V to V
. A chan-
REF
nel 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-and-hold mode into hold mode and initiates a conversion. If the pulse is less than 4 µs,
an internal timer ensures that the track-and-hold does not go into hold and conversion is not initiated
until the power-up time has elapsed. The track-and-hold goes into track mode again at the end of conversion. (See Operating Mode section.)
AD7417 PIN CONFIGURATION
SOIC/TSSOP
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
REV. G–4–
Page 5
AD7416/AD7417/AD7418
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
AD7416 PIN FUNCTION DESCRIPTION
Pin No.MnemonicDescription
1SDADigital I/O. Serial bus bidirectional data. Push-pull output.
2SCLDigital Input. Serial bus clock.
3OTIThis is a logic output. The OTI is set if the result of a conversion on Channel 0 (temperature sensor) is
greater that an 8-bit word in the OTR. The signal is reset at the end of a serial read operation. Opendrain output.
4GNDGround reference for track-and-hold, comparator and capacitor DAC, and digital circuitry.
5A2Digital Input. The highest programmable bit of the serial bus address.
6A1Digital Input. The middle programmable bit of the serial bus address.
7A0Digital 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.MnemonicDescription
1SDADigital I/O. Serial bus bidirectional data. Push-pull output.
2SCLDigital Input. Serial bus clock.
3OTIThis is a logic output. The OTI is set if the result of a conversion on Channel 0 (temperature sensor) is
greater that an 8-bit word in the OTR. The signal is reset at the end of a serial read operation. Opendrain output.
4GNDGround reference for track-and-hold, comparator and capacitor DAC, and digital circuitry.
5A
6REF
7V
IN
IN
DD
8CONVSTLogic Input Signal. Convert start signal. The rising edge of this signal fully powers up the part. The
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 to the
REF
configuration register of the AD7418 and choosing Channel 4. (See Control Byte section.)
Reference Input. An external 2.5 V reference can be connected to the AD7418 at this pin. To enable the
on-chip reference, the REF
pin should be tied to GND. If an external reference is connected to the
IN
AD7418, the internal reference will shut down.
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 ofCONVST places the track-and-hold mode into hold mode and initiates a conversion. If the pulse is less
than 4 µs, an internal timer ensures that the track-and-hold does not go into hold and conversion is not
initiated until the power-up time has elapsed. The track-and-hold goes into track mode again at the end
of conversion. (See Operating Mode section.)
REV. G
AD7416 PIN CONFIGURATION
SOIC/MSOP
1
SDA
2
OTI
AD7416
TOP VIEW
3
(Not to Scale)
4
SCL
GND
AD7418 PIN CONFIGURATION
SOIC/MSOP
8
V
DD
7
A0
6
A1
5
A2
–5–
Page 6
AD7416/AD7417/AD7418
ABSOLUTE MAXIMUM RATINGS
1
(TA = 25°C, unless otherwise noted.)
to AGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
V
DD
to DGND . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V
V
DD
Analog Input Voltage to AGND
A
to 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 VDD + 0.3 V
DD
DD
+ 0.3 V
+ 0.3 V
Operating Temperature Range
A Version . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to +125°C
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
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.
REV. G–6–
Page 7
ORDERING GUIDE
AD7416/AD7417/AD7418
ModelRangeErrorDescriptionBrandingOption
AD7416ACHIPSDie
AD7416AR–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7416AR-REEL–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7416AR-REEL7–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7416ARZ*–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7416ARZ-REEL*–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7416ARZ-REEL7*–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7416ARM–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C6ARM-8
AD7416ARM-REEL–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C6ARM-8
AD7416ARM-REEL7–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C6ARM-8
AD7416ARMZ*–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C6ARM-8
AD7416ARMZ-REEL*–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C6ARM-8
AD7416ARMZ-REEL7*–40°C to +125°C±2°C8-Lead Micro Small Outline Package (MSOP)C6ARM-8
AD7417ACHIPSDie
AD7417AR–40°C to +125°C± 2°C16-Lead Standard Small Outline Package (SOIC)RN-16
AD7417AR-REEL–40°C to +125°C± 2°C16-Lead Standard Small Outline Package (SOIC)RN-16
AD7417AR-REEL7–40°C to +125°C± 2°C16-Lead Standard Small Outline Package (SOIC)RN-16
AD7417ARU– 40°C to +125°C± 2°C16-Lead Thin Shrink Small Outline Package (TSSOP)RU-16
AD7417ARU-REEL–40°C to +125°C± 2°C16-Lead Thin Shrink Small Outline Package (TSSOP)RU-16
AD7417ARU-REEL7–40°C to +125°C± 2°C16-Lead Thin Shrink Small Outline Package (TSSOP)RU-16
AD7417BR–40°C to +85°C± 1°C16-Lead Standard Small Outline Package (SOIC)RN-16
AD7417BR-REEL–40°C to +85°C± 1°C16-Lead Standard Small Outline Package (SOIC)RN-16
AD7417BR-REEL7–40°C to +85°C± 1°C16-Lead Standard Small Outline Package (SOIC)RN-16
AD7418ACHIPSDie
AD7418AR–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7418AR-REEL–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7418AR-REEL7–40°C to +125°C± 2°C8-Lead Standard Small Outline Package (SOIC)RN-8
AD7418ARM–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C7ARM-8
AD7418ARM-REEL–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C7ARM-8
AD7418ARM-REEL7–40°C to +125°C± 2°C8-Lead Micro Small Outline Package (MSOP)C7ARM-8
AD7418ARUZ*–40°C to +125°C± 2°C16-Lead Thin Shrink Small Outline Package (TSSOP)RU-16
AD7418ARUZ-REEL*–40°C to +125°C± 2°C16-Lead Thin Shrink Small Outline Package (TSSOP)RU-16
AD7418ARUZ-REEL7*–40°C to +125°C± 2°C16-Lead Thin Shrink Small Outline Package (TSSOP)RU-16
EVAL-AD7416/AD7417/Evaluation Board
AD7418EB
*Pb-Free Part
TemperatureTemperature PackagePackage
REV. G
–7–
Page 8
AD7416/AD7417/AD7418
(continued from page 1)
2
An I
C compatible serial interface allows the AD7416/AD7417/
AD7418 registers to be written to and read back. The three LSBs
of the AD7416/AD7417’s serial bus address can be selected,
which allows up to eight AD7416/AD7417s to be connected to
a single bus.
The AD7417 is available in a narrow body, 0.15'', 16-lead, small
outline IC (SOIC) and in a 16-lead, thin shrink, small outline
package (TSSOP). The AD7416 and AD7418 are available in
8-lead SOIC and MSOP packages.
PRODUCT HIGHLIGHTS
1. The AD7416/AD7417/AD7418 have an on-chip temperature
sensor that allows an accurate measurement of the ambient
temperature (±1°C @ 25°C, ± 2°C overtemperature) to be
made. The measurable temperature range is –40°C to +125°C.
An overtemperature indicator is implemented by carrying
out a digital comparison of the ADC code for Channel 0
(temperature sensor) with the contents of the on-chip overtemperature register.
2. The AD7417 offers a space-saving 10-bit A/D solution with
four external voltage input channels, an on-chip temperature
sensor, an on-chip reference, and clock oscillator.
3. The automatic power-down feature enables the AD7416/
AD7417/AD7418 to achieve superior power performance. At
slower throughput rates, the part can be programmed to
operate in a low power shutdown mode, allowing further
savings in power consumption.
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-and-Hold Acquisition Time
Track-and-hold acquisition time is the time required for the
output of the track-and-hold amplifier to reach its final value,
within ± 1/2 LSB, after the end of conversion (the point at which
the track-and-hold returns to track mode). It also applies to
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
IN
means that the user must wait for the duration of the track-andhold acquisition time after the end of conversion or after a channel
change/step input change to A
before starting another conver-
IN
sion, to ensure that the part operates to specification.
CIRCUIT INFORMATION
The AD7417 and AD7418 are single-channel and four-channel,
15 µs conversion time, 10-bit ADCs with on-chip temperature
sensor, reference, and serial interface logic functions on a single
chip. The AD7416 has no analog input channel and is intended
for temperature measurement only. The ADC section consists
of a conventional successive approximation converter based
around a capacitor DAC. The AD7416, AD7417, and AD7418
are capable of running on a 2.7 V to 5.5 V power supply, and
the AD7417 and AD7418 accept an analog input range of 0 V
to +VREF. The on-chip temperature sensor allows an accurate
measurement of the ambient device temperature to be made.
The working measurement range of the temperature sensor is
–40°C to +125°C. The parts require a 2.5 V reference that can
be provided from the part’s own internal reference or from an
external reference source.
CONVERTER DETAILS
Conversion is initiated on the AD7417/AD7418 by pulsing the
CONVST input. The conversion clock for the part is internally
generated so no external clock is required except when reading
from and writing to the serial port. The on-chip track-and-hold
goes from track to hold mode and the conversion sequence is
started on the falling edge of the CONVST signal. A conversion
is also initiated in the automatic conversion mode every time a
read or write operation to the AD7416/AD7417/AD7418 takes
place. In this case, the internal clock oscillator (which runs the
automatic conversion sequence) is restarted at the end of the
read or write operation. The track-and-hold goes into hold
approximately 3 µs after the read or write operation is complete
and a conversion is then initiated. The result of the conversion
is available either 15 µs or 30 µs later, depending on whether an
analog input channel or the temperature sensor is selected. The
track-and-hold acquisition time of the AD7417/AD7418 is 400 ns.
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. Tempera-
ture 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).
All unused analog inputs should be tied to a voltage within the
nominal analog input range to avoid noise pickup. For minimum power consumption, the unused analog inputs should be
tied to GND.
REV. G–8–
Page 9
AD7416/AD7417/AD7418
TYPICAL CONNECTION DIAGRAM
Figure 2 shows a typical connection diagram for the AD7417.
Using the A0, A1, and A2 pins allows the user to select from up
to eight AD7417s on the same serial bus, if desired. An external
2.5 V reference can be connected at the REF
pin. If an exter-
IN
nal reference is used, a 10 µF capacitor should be connected
between REF
and GND. SDA and SCL form the 2-wire I2C
IN
compatible interface. For applications where power consumption is of concern, the automatic power-down at the end of a
conversion should be used to improve power performance. See
Operating Modes section of this data sheet.
SUPPLY
2.7V TO
OPTIONAL
EXTERNAL
REFERENCE
5.5V
0V TO 2.5V
INPUT
AD780/
REF-192
A
IN1
A
IN2
A
IN3
A
IN4
GND
0.1F10F
V
AD7417
REF
DD
SCL
SDA
CONVST
OTI
IN
10F FOR
EXTERNAL
REFERENCE
2-WIRE
SERIAL
INTERFACE
A0
A1
A2
C/P
Figure 2. Typical Connection Diagram
ANALOG INPUTS
Figure 3 shows an equivalent circuit of the analog input structure of the AD7417 and AD7418. The two diodes, D1 and D2,
provide ESD protection for the analog inputs. Care must be
taken to ensure that the analog input signal never exceeds the
supply rails by more than 200 mV. This will cause these diodes
to become forward-biased and start conducting current into the
substrate. The maximum current these diodes can conduct
without causing irreversible damage to the part is 20 mA. The
capacitor C2 in Figure 3 is typically about 4 pF and can primarily be attributed to pin capacitance. The resistor R1 is a lumped
component made up of the on resistance of a multiplexer and a
switch. This resistor is typically about 1 kΩ. The capacitor C1 is
the ADC sampling capacitor and has a capacitance of 3 pF.
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 4)
IN
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
1.2V
SW1
+
26k⍀
24k⍀
2.5V
EXTERNAL
REFERENCE
DETECT
+
BUFFER
Figure 4. On-Chip Reference
TEMPERATURE MEASUREMENT
A common method of measuring temperature is to exploit the
negative temperature coefficient of a diode, or the base-emitter
voltage of a transistor, operated at a constant current. Unfortunately, this technique requires calibration to null out the effect
of the absolute value of V
, which varies from device to device.
BE
The technique used in the AD7416/AD7417/AD7418 is to
measure the current change in V
when the device is operated
BE
at two different currents.
This is given by
∆VKTqnN
=×
/1
BE
()
where:
K is Boltzmann’s constant.
q is the charge on the electron (1.6 × 10
-19
Coulombs).
T is the absolute temperature in Kelvins.
N is the ratio of the two currents.
V
DD
I
N ⴛ I
V
DD
D1
A
IN
4pF
C2
D2
R1
1k⍀
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 that is gained up by a switched capacitor amplifier to
give an output of 2.5 V. The amplifier is only powered up at the
REV. G
–9–
SENSING
TRANSISTOR
SENSING
TRANSISTOR
Figure 5. Temperature Measurement Technique
V
OUTⴙ
TO ADC
V
OUTⴚ
Page 10
AD7416/AD7417/AD7418
Figure 5 shows the method the AD7416/AD7417/AD7418 uses
to measure the device temperature. To measure ⌬V
, the sen-
BE
sor (substrate transistor) is switched between operating currents
of I and N × I. The resulting waveform is passed through a
chopper-stabilized amplifier that performs the functions of
amplification and rectification of the waveform to produce a dc
voltage proportional to ⌬V
BE
.
This voltage is measured by the ADC to give a temperature
output in 10-bit twos complement form.
The temperature resolution of the ADC is 0.25°C, which corresponds to 1 LSB of the ADC. The ADC can theoretically measure
a temperature span of 255°C; the guaranteed temperature range
is –40°C to +125°C. The result of the conversion is stored in
the Temperature Value Register (00h) as a 16-bit word. The
10 MSBs of this word store the temperature measurement (see
Table III and Table IV).
The temperature conversion formula using the 10 MSBs of the
Temperature Value Register is
1. Positive Temperature = ADC Code/4
2. Negative Temperature = (ADC Code* – 512)/4
*MSB is removed from the ADC Code.
INTERNAL REGISTER STRUCTURE
The AD7417/AD7418 has seven internal registers, as shown in
Figure 6. Six of these are data registers and one is an Address
Pointer Register. The AD7416 has five internal registers (the
ADC and Config2 Registers are not applicable to the AD7416).
TEMPERATURE
VALUE
REGISTER
(READ-ONLY
ADDRESS 00h)
CONFIGURATION
REGISTER
(READ/WRITE
ADDRESS 01h)
T
SETPOINT
HYST
REGISTER
(READ/WRITE
ADDRESS 02h)
ADDRESS POINTER REGISTER
The Address Pointer Register is an 8-bit register that stores an
address that points to one of the six data registers. The first data
byte of every serial write operation to the AD7416/AD7417/
AD7418 is the address of one of the data registers, which is
stored in the Address Pointer Register, and selects the data
register to which subsequent data bytes are written. Only the
three LSBs of this register are used to select a data register.
Table I. Address Pointer Register
P7*P6*P5*P4*P3*P2P1P0
00 000 Register Select
*P3 to P7 must be set to 0.
Table II. Register Addresses
P2P1P0Registers
000Temperature Value (Read-Only)
001Config Register (Read/Write)
010T
011T
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 D14D13D12 D11 D10D9D8D7D6
MSB B8B7B6B5B4B3B2B1LSB
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.
The Configuration Register is an 8-bit, read/write register that
is used to set the operating modes of the AD7416/AD7417/
AD7418. Bits D7 to D5 control the channel selection as
outlined in Table VI. These bits should always be 0, 0, 0 for
the AD7416. Bits D4 and D3 are used to set the length of the
fault queue. D2 sets the sense of the OTI output. D1 selects
the comparator or interrupt mode of operation, and D0 = 1
selects the shutdown mode (Default D0 = 0).
The AD7416 contains a temperature-only channel, the
AD7417 has four analog input channels and a temperature
channel, and the AD7418 has two channels, a temperature
channel, and an analog input channel. The temperature channel address for all parts is the same, CH0. The address for the
analog input channel on the AD7418 is CH4. Table VI outlines
the channel selection on the parts, while Table VII shows the
fault queue settings. D1 and D2 are explained in the OTI Output section.
Table VI. Channel Selection
D7D6D5Channel Selection
00 0Temperature Sensor (All Parts)
00 1 A
01 0 A
01 1 A
10 0 A
(AD7417 Only)
IN1
(AD7417 Only)
IN2
(AD7417 Only)
IN3
(AD7417) and AIN (AD7418)
IN4
Table VII. Fault Queue Settings
D4D3Number of Faults
00 1 (Power-Up Default)
01 2
10 4
11 6
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. ADC Value Register
D15D14 D13 D12D11 D10D9D8D7D6
MSBB8B7B6B5B4B3B2B1LSB
ADC Transfer Function
The designed code transitions occur at successive integer LSB
values (i.e., 1 LSB, 2 LSB, and so on). The LSB size = VREF/
1024. The ideal transfer function characteristic for the AD7417
and AD7418 ADC is shown in Figure 7.
111...111
111...110
111...000
011...111
ADC CODE
000...010
000...001
000...000
0V 1/2LSB+VREF – 1LSB
1LSB = VREF/1024
ANALOG INPUT
Figure 7. Ideal Transfer Function Characteristic
for the AD7417/AD7418
CONFIG2 REGISTER (ADDRESS 05h)
A second configuration register is included in the AD7417/
AD7418 for the functionality of the CONVST pin. It is an 8-bit
register with Bits D5 to D0 being left at 0. Bit D7 determines
whether the AD7417/AD7418 should be operated in its default
mode (D7 = 0), performing conversions every 355 µs or in itsCONVST 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. CONFIG2 Register
T
SETPOINT REGISTER (ADDRESS 02h)
HYST
The T
nine MSBs store the T
Setpoint Register is a 16-bit, read/write register whose
HYST
setpoint in twos complement for-
HYST
mat equivalent to the nine MSBs of the Temperature Value
Register. Bits 6 to 0 are unused.
T
SETPOINT REGISTER (ADDRESS 03h)
OTI
The T
whose nine MSBs store the T
Setpoint Register is a 16-bit, read/write register
OTI
setpoint in twos complement
OTI
format equivalent to the nine MSBs of the Temperature Value
Register. Bits 6 to 0 are unused.
Table VIII. Setpoint Registers
D15D14D13D12D11D10D9D8D7
MSBB7B6B5B4B3B2B1 LSB
REV. G
D7D6D5D4D3D2D1D0
Conversion ModeTest 1 000000
SERIAL BUS INTERFACE
Control of the AD7416/AD7417/AD7418 is carried out via the
2
C compatible serial bus. The AD7416/AD7417/AD7418 is
I
connected to this bus as a slave device, under the control of a
master device, e.g., the processor.
SERIAL BUS ADDRESS
As with all I2C compatible devices, the AD7416/AD7417/AD7418
have a 7-bit serial address. The four MSBs of this address for the
AD7416 are set to 1001; the AD7417 are set to 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, up
DD
to eight AD7416/AD7417s can be connected to a single serial bus,
–11–
Page 12
AD7416/AD7417/AD7418
or the addresses can be set to avoid conflicts with other devices
on the bus. The four MSBs of this address for the AD7418 are set
to 0101, while the three LSBs are all set to zero.
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 7-bit address (MSB first) plus an R/W bit, which determines the direction of the data transfer, i.e., whether data
will be written to or read from the slave device.
The peripheral whose address corresponds to the transmitted
address responds by pulling the data line low during the low
period before the ninth clock pulse, known as the Acknowledge bit. All other devices on the bus now remain idle while
the selected device waits for data to be read from or written
to it. If the R/W bit is a 0, then the master will write to the
slave device. If the R/W bit is a 1, then the master will read
from the slave device.
2. Data is sent over the serial bus in sequences of nine clock
pulses, eight bits of data followed by an Acknowledge bit
from the receiver of data. Transitions on the data line must
occur during the low period of the clock signal and remain
stable during the high period, since a low-to-high transition
when the clock is high may be interpreted as a stop signal.
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
191
SCL
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 8. The write operation consists of the
serial bus address followed by the address pointer byte. No
data is written to any of the data registers.
2. Writing a single byte of data to the configuration registers or
to the 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
written to the T
OTI
and T
and T
OTI
, and only eight bits need be
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
9
SDA
START BY
MASTER
001A2
FRAME 1
SERIAL BUS ADDRESS BYTE
A0
A1
R/W
ACK. BY
AD7416
P6
P7
P5P4
ADDRESS POINTER REGISTER BYTE
P3
FRAME 2
P1
P2
P0
ACK. BY
AD7416
STOP BY
MASTER
1
Figure 8. Writing to the Address Pointer Register to Select a Data Register for a Subsequent Read Operation
SCL
SDA
START BY
MASTER
19
001A2A1A0P7P 6P5
1
FRAME 1
SERIAL BUS ADDRESS BYTE
SCL (CONTINUED)
SDA (CONTINUED)
R/W
ACK. BY
AD7416
1
P3P2P1P0
P4
ADDRESS POINTER REGISTER BYTE
19
D6D5
D7
D4
FRAME 2
D3D2D1D0
FRAME 3
DATA BYTE
ACK. BY
AD7416
9
ACK. BY
AD7416
STOP BY
MASTER
Figure 9. Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Data Register
REV. G–12–
Page 13
AD7416/AD7417/AD7418
the Address Pointer Register, followed by the data byte written to the selected data register. This is illustrated in Figure 9.
3. Writing two bytes of data to the T
OTI
or T
HYST
Register.
If 9-bit resolution is required for the temperature setpoints,
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, followed by
two data bytes written to the selected data register. This is
illustrated in Figure 10.
READING DATA FROM THE AD7416/AD7417/AD7418
Reading data from the AD7416/AD7417/AD7418 is a one or
two byte operation. Reading back the contents of the Configuration Register is a single byte read operation, as shown in Figure
11, the register address previously having been set by a singlebyte write operation to the Address Pointer Register.
Reading data from the temperature value, T
ter, is a two-byte operation, as shown in Figure 12. It is also
possible to read the most significant bit of a 9-bit/10-bit register
in this manner.
191
SCL
SDA00
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
D7D 6
STOP BY
MASTER
P4P3P2P1P0
P5
ADDRESS POINTER REGISTER BYTE
FRAME 2
D4D3
D5
LEAST SIGNIFICANT DATA BYTE
FRAME 4
Figure 10. Writing to the Address Pointer Register Followed by Two Bytes of Data to the T
D2
D1
ACK. BY
AD7416
OTI
9
D0
or T
OTI
ACK. BY
AD7416
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
D7D6D5D4D3D2D1D0
AD7416
SINGLE DATA BYTE FROM AD7416
FRAME 2
NO ACK. BY
MASTER
STOP BY
MASTER
Figure 11. Reading a Single Byte of Data from the Configuration Register
19
001A2A1A0D15 D14 D13
1
FRAME 1
SERIAL BUS ADDRESS BYTE
SCL (CONTINUED)
SDA (CONTINUED)
R/W
ACK. BY
AD7416
Figure 12. Reading Two Bytes of Data from the T
1
D11 D10D9D8
D12
MOST SIGNIFICANT DATA BYTE FROM AD7416
19
D6D5
D7
LEAST SIGNIFICANT DATA BYTE FROM AD7416
D4
OTI
FRAME 2
D3D2D1D0
FRAME 3
or T
HYST
Register
NO ACK. BY
MASTER
9
ACK. BY
MASTER
STOP BY
MASTER
REV. G
–13–
Page 14
AD7416/AD7417/AD7418
Please note that when reading back from the ADT7416/
ADT7417/ADT7418, no more than three bytes of data must be
read back. A STOP command must be inserted at the end of
the read communication. If a STOP command is not inserted
by the master and the ADT7416/ADT7417/ADT7418 receives
more SCL cycles than the maximum needed for three bytes of
data, then the I
2
C interface on the ADT7416/ADT7417/
ADT7418 will pull the SDA line low and prevent it from going
high again. To recover the ADT7416/ADT7417/ADT7418
interface the part must be powered off and on again. Reference
the application note, AN-686, on the Analog Devices website
for more information on I
2
C interfaces.
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
ture falls below T
HYST
and remains active until the tempera-
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
*
IN INTERRUPT MODE, A READ OPERATION OR SHUTDOWN RESETS THE OTI
OUTPUT; OTHERWISE THE OTI OUTPUT REMAINS ACTIVE INDEFINITELY, ONCE
TRIGGERED.
READ*READ*READ*READ*READ*READ*READ
*
Figure 13. Operation of OTI Output (Shown Active Low)
The open-drain configuration of OTI allows the OTI outputs of
several AD7416/AD7417/AD7418s to be wire-ANDed together
when in active low mode.
The OTI output is used to indicate that an out-of-limit temperature excursion has occurred. OTI is an open-drain output
that can be programmed to be active low by setting Bit D2 of
the Configuration Register to 0 or active high by setting Bit D2
of the Configuration Register to 1.
In the interrupt mode (D1 = 1), the OTI output becomes active
when the temperature exceeds T
the temperature falls below T
HYST
and remains active even if
OTI
, until it is reset by a read operation. Once OTI has become active by the temperature exceeding
T
, and has then been reset, it will remain inactive even if the
OTI
temperature remains, or subsequently rises again, above T
OTI
. It
will not become active again until the temperature falls below
T
. It will then remain active until reset by a read opera-
HYST
tion. Once OTI has become active by the temperature falling
below T
temperature remains, or subsequently falls again, below T
and then reset, it will remain inactive even if the
HYST
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
DD
allow interfacing between 5 V and 3.3 V systems) provided that
the maximum voltage rating of the OTI output is not exceeded.
The value of the pull-up resistor depends on the application but
should be as large as possible to avoid excessive sink currents at
the OTI output, which can heat the chip and affect the temperature reading. The maximum value of the pull-up resistor that
will meet the output high current specification of the OTI output is 30 kΩ, but higher values may be used if a lower output
current is required. For most applications, a value of 10 kΩ will
prove suitable.
FAULT QUEUE
To avoid false triggering of the AD7416/AD7417/AD7418 in
noisy environments, a fault queue counter is provided that can
be programmed by Bits D3 and D4 of the Configuration Register (see Table V) to count 1, 2, 4, or 6 fault events before OTI
becomes active. In order to trigger OTI, the faults must occur
consecutively. For example, if the fault queue is set to 4, then
four consecutive temperature measurements greater than T
(or less than T
) must occur. Any reading that breaks the
HYST
OTI
sequence will reset the fault queue counter, so if there are three
readings greater than T
followed by a reading less than T
OTI
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
= 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 standalone 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 the current until
the next conversion occurs.
Two situations can arise in this mode on the request of a temperature read. If a read occurs during a conversion, the conversion
aborts and a new one starts on the stop/repeat start condition.
The temperature value that is read is that of the previous completed conversion. The next conversion will typically occur
400 µs after the new conversion has begun.
If a read is called between conversions, a conversion is initiated
on the stop/repeat start condition. After this conversion, the part
returns to performing a conversion every 400 µs.
REV. G–14–
Page 15
AD7416/AD7417/AD7418
With a VDD = 3 V, for each 400 µs cycle, the AD7416 spends
40 µs (or 10% of the time) in conversion mode. It spends 360 µs
(or 90% of time) in partial power-down mode. Thus, the average power dissipated by the AD7416/AD7417/AD7418 is
301109 12mW ×+×=...mWmW
Mode 2
For applications where temperature measurements are required at
a slower rate, e.g., every second, power consumption of the part
can be reduced by writing to the part to go to a full power-down
between reads. The current consumption in full power-down is
typically 0.2 µA and full power-down is initiated when D0 = 1
in the Configuration Register. When a measurement is required,
a write operation can be performed to power-up the part. The
part then performs a conversion and is returned to power-down.
The temperature value can be read in the full power-down
because the I
2
C bus is continuously active.
The power dissipation in this mode depends on the rate at which
reads take place. Taking the requirements for a temperature
measurement every 100 ms as an example, the optimum power
dissipation is achieved by placing the part in full 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
30004 600 9996 1 2mWnWW×+ × =...µ
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
read time with the I
2
OTI
C operating at 100 kbit/s would be 270 µs.
and T
are 2-byte reads, the
HYST
If temperature reads are called too often, reads will overlap
with conversions, aborting them continuously, which results in
invalid readings.
CONVERT START MODE
The AD7417/AD7418 has an extra mode, set by writing to the
MSB of the Config2 Register.
CONVST Pin Mode
By setting the CONVST Mode Bit to 1, conversions are initiated
only by using the CONVST pin. In this method of operation,
CONVST is normally low.
The rising edge of CONVST starts the power-up time. This
power-up time is 4 µs. If the CONVST high time is longer than
4 µs, a conversion is initiated on the falling edge of CONVST
and the track-and-hold also enters its hold mode at this time. If
the CONVST high time is less than 4 µs, an internal timer,
initiated by the rising edge of CONVST holds off the track-andhold and the initiation of conversion until the timer times out
(4 µs after the rising edge of CONVST, which corresponds with
the power-up time). CONVST input remains low at the end of
conversion, thus causing the part to enter its power-down mode.
In this method of operation, CONVST is normally low with a
high going pulse controlling the power-up and conversion starts.
The CONVST pin should not be pulsed when reading from or
writing to the port.
Figure 17 shows the recommended minimum times for the
CONVST pulse when the temperature channel is selected.
Figure 18 shows the minimum times an analog input channel
is selected.
APPLICATIONS INFORMATION
SUPPLY DECOUPLING
The AD7416/AD7417/AD7418 should be decoupled with a
0.1 µF ceramic capacitor between V
and GND. This is
DD
particularly important if the part is mounted remote from the
power supply.
POWER-ON-RESET
To ensure proper power-on-reset, make sure that the supply
voltage on the V
pin is at 0 V. Refer to application note
DD
AN-588 for more information. A failed power-on-reset can
prevent the default values from being loaded into the AD7416/
AD7417/AD7418 registers. If the correct values are not loaded
into the registers, then the device will not start operating. The
output from the value registers will be a constant value.
To get the device operating again, the registers will have to be
loaded with their default values via the I
2
C bus. Therefore, in
the event of an inadequate power-on-reset and for all three
devices, the following registers should be loaded with their
default values:
Configuration Register 1—Default Value = 00h
Configuration Register 2—Default Value = 00h
T
Setpoint Register—Default Value = 4B00h
HYST
Setpoint Register—Default Value = 5500h
T
OTI
MOUNTING THE AD7416
The AD7416/AD7417/AD7418 can be used for surface or air
temperature sensing applications. If the device is cemented to a
surface with thermally conductive adhesive, the die temperature
will be within about 0.2°C of the surface temperature, thanks to
the device’s low power consumption. Care should be taken to
insulate the back and leads of the device from the air, if the
ambient air temperature is different from the surface temperature being measured.
The ground pin provides the best thermal path to the die, so the
temperature of the die will be close to that of the printed circuit
ground track. Care should be taken to ensure that this is in good
thermal contact with the surface being measured.
As with any IC, the AD7416/AD7417/AD7418 and its associated wiring and circuits must be kept free from moisture to
prevent leakage and corrosion, particularly in cold conditions
where condensation is more likely to occur. Water resistant
varnishes and conformal coatings can be used for protection.
The small size of the AD7416 package allows it to be mounted
inside sealed metal probes that provide a safe environment for
the device.
REV. G
–15–
Page 16
AD7416/AD7417/AD7418
C
FAN CONTROLLER
Figure 14 shows a simple fan controller that will switch ON a
cooling fan when the temperature exceeds 80°C and switch it
OFF again when the temperature falls below 75°C. The AD7416
can be used standalone in this application or with a serial bus
interface if different trip temperatures are required. If the AD7416
is used with a bus interface, the sense of OTI can be set to active
high, Q1 and R1 can be omitted, and OTI can be connected
directly to the gate of Q2 with R2 as the pull-up resistor.
12V
V
DD
3V TO 5.5V
Q2
LOGIC LEVEL
MOSFET RATED
TO SUIT FAN
CURRENT
AD7416
R1
10k⍀
R2
10k⍀
Q1
2N3904
OR SIMILAR
Figure 14. AD7416 Used as a Fan Controller
V
DD
3V TO 5.5V
THERMOSTAT
Figure 15 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
. For this application and for comparator mode, the OTI
OTI
output should be programmed active low.
V
DD
3V TO
5.5V
AD7416
R1
10k⍀
RELAY
Q1
2N3904
OR SIMILAR
D1
1N4001
HEATER
RLA1
HEATER
SUPPLY
Figure 15. 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 16 shows a system in which eight AD7416s are connected
to a single serial bus, with their OTI outputs wire-ANDed
together to form a common interrupt line. This arrangement
does mean that each device must be read to determine which
one has generated the interrupt, and if a unique interrupt is
required for each device, the OTI outputs can be connected
separately to the I/O chip.
AD7416
CONVST
Figure 17.
R1
10k⍀
100ns
CONVST
AD7416
AD7416
AD7416
Figure 16. Multiple Connection of AD7416s to a Single Serial Bus
40s
When Temperature Channel Selected
AD7416
Figure 18.
AD7416
ONVST
100ns
CONVST
SUPER I/O CHIP
AD7416
15s
AD7416
When VIN Channel(s) Selected
PROCESSOR
REV. G–16–
Page 17
OUTLINE DIMENSIONS
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
0.50 (0.0196)
0.25 (0.0099)
ⴛ 45ⴗ
8ⴗ
0ⴗ
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0040)
85
41
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
1.27 (0.0500)
BSC
6.20 (0.2440)
5.80 (0.2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
COMPLIANT TO JEDEC STANDARDS MS-012AA
AD7416/AD7417/AD7418
16-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-16)
Dimensions shown in millimeters and (inches)
10.00 (0.3937)
9.80 (0.3858)
4.00 (0.1575)
3.80 (0.1496)
0.25 (0.0098)
0.10 (0.0039)
COPLANARITY
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
16
1
1.27 (0.0500)
BSC
0.51 (0.0201)
0.10
0.31 (0.0122)
COMPLIANT TO JEDEC STANDARDS MS-012AC
9
6.20 (0.2441)
5.80 (0.2283)
8
1.75 (0.0689)
1.35 (0.0531)
SEATING
PLANE
0.25 (0.0098)
0.17 (0.0067)
0.50 (0.0197)
0.25 (0.0098)
8ⴗ
0ⴗ
1.27 (0.0500)
0.40 (0.0157)
ⴛ 45ⴗ
16-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-16)
Dimensions shown in millimeters
8-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
16
4.50
4.40
4.30
PIN 1
0.15
0.05
0.65
BSC
5.10
5.00
4.90
9
6.40
BSC
81
1.20
MAX
0.30
0.19
COPLANARITY
0.10
COMPLIANT TO JEDEC STANDARDS MO-153AB
SEATING
PLANE
0.20
0.09
8ⴗ
0ⴗ
0.75
0.60
0.45
3.00
BSC
85
3.00
BSC
1
PIN 1
0.65 BSC
0.15
0.00
0.38
0.22
COPLANARITY
0.10
COMPLIANT TO JEDEC STANDARDS MO-187AA
4
SEATING
PLANE
4.90
BSC
1.10 MAX
0.23
0.08
8ⴗ
0ⴗ
0.80
0.60
0.40
Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C
Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.