Single- and 4-Channel, 9 s, 10-Bit ADCs
a
with On-Chip Temperature Sensor
AD7816/AD7817/AD7818
FUNCTIONAL BLOCK DIAGRAM
FEATURES
10-Bit ADC with 9 s Conversion Time
One (AD7818) and Four (AD7817) Single-Ended Analog
Input Channels
The AD7816 Is a Temperature Measurement Only Device
On-Chip Temperature Sensor
V
REF
DD
IN
AD7817
OVER-TEMP
REG
OTI
A > B
A
B
TEMP
SENSOR
CHARGE
REDISTRIBUTION
DAC
REF
2.5V
DATA
OUT
D
OUT
Resolution of 0.25؇C
V
IN1
IN2
IN3
؎2؇C Error from –40؇C to +85؇C
–55؇C to +125؇C Operating Range
Wide Operating Supply Range
+2.7 V to +5.5 V
Inherent Track-and-Hold Functionality
On-Chip Reference (2.5 V ؎ 1%)
Over-Temperature Indicator
V
V
MUX
CONTROL
LOGIC
CONTROL
REG
SAMPLING
CAPACITOR
D
IN
V
SCLK
IN4
RD/WR
CLOCK
V
BALANCE
CS
BUSY
AGND
DGND
CONVST
Automatic Power-Down at the End of a Conversion
Low Power Operation
4 W at a Throughput Rate of 10 SPS
40 W at a Throughput Rate of 1 kSPS
400 W at a Throughput Rate of 10 kSPS
Flexible Serial Interface
The AD7816, AD7817 and AD7818 have a flexible serial inter-
face that allows easy interfacing to most microcontrollers.
The interface is compatible with the Intel 8051, Motorola
SPI™ and QSPI™ protocols and National Semiconductors
MICROWIRE™ protocol. For more information refer to the
Serial Interface section of this data sheet.
APPLICATIONS
Ambient Temperature Monitoring (AD7816)
Thermostat and Fan Control
High Speed Microprocessor
Temperature Measurement and Control
Data Acquisition Systems with Ambient Temperature
Monitoring (AD7817 and AD7818)
Industrial Process Control
The AD7817 is available in a narrow body 0.15" 16-lead Small
Outline IC (SOIC), in a 16-lead, Thin Shrink Small Outline
Package (TSSOP), while the AD7816/AD7818 come in an
8-lead Small Outline IC (SOIC) and an 8-lead microsmall
Outline IC (µSOIC).
Automotive
Battery Charging Applications
PRODUCT HIGHLIGHTS
1. The devices have an on-chip temperature sensor that allows an
accurate measurement of the ambient temperature to be
made. The measurable temperature range is –55°C to +125°C.
GENERAL DESCRIPTION
The AD7818 and AD7817 are 10-bit, single- and 4-channel
A/D converters with on-chip temperature sensor that can oper-
ate from a single 2.7 V to 5.5 V power supply. Each part con-
tains a 9 µs successive-approximation converter based around
a capacitor DAC, an on-chip temperature sensor with an accu-
racy of ±2°C, an on-chip clock oscillator, inherent track-and-
hold functionality and an on-chip reference (2.5 V). The
AD7816 is a temperature monitoring only device in a SOIC/
µSOIC package.
2. An over-temperature indicator is implemented by carrying
out a digital comparison of the ADC code for Channel 0
(temperature sensor) with the contents of the on-chip over-
temperature register. The over-temperature indicator pin goes
logic low when a predetermined temperature is exceeded.
3. The automatic power-down feature enables the AD7816,
AD7817 and AD7818 to achieve superior power perfor-
mance at slower throughput rates, e.g., 40 µW at 1 kSPS
throughput rate.
The on-chip temperature sensor of the AD7817 and AD7818
can be accessed via 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
with a resolution of ±0.25°C. See Measuring Temperature section
of the data sheet.
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corporation.
REV. A
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.
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© Analog Devices, Inc., 2000