AD7816 Datasheet, PDF (1/20 Pages) Analog Devices – Single- and 4-Channel, 9 us, 10-Bit ADCs with On-Chip Temperature Sensor

Single- and 4-Channel, 9 ␮s, 10-Bit ADCs
with On-Chip Temperature Sensor
AD7816/AD7817/AD7818
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
Resolution of 0.25؇C
؎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%)
Overtemperature Indicator
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
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
Automotive
Battery Charging Applications
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 Ϯ2°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/
MSOP package.
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 Ϯ0.25°C. See Temperature Measurement
section of this data sheet.
FUNCTIONAL BLOCK DIAGRAM
REF_IN
V_DD
AD7817
V_IN1
V_IN2
V_IN3
V_IN4
TEMP
SENSOR
REF
2.5V
MUX
SAMPLING
CAPACITOR
OVERTEMP
REG
B
CHARGE
REDISTRIBUTION
DAC
A>B
A
DATA
OUT
CONTROL
LOGIC
CONTROL
REG
V_BALANCE
CLOCK
AGND DGND
BUSY
CONVST
OTI
D_OUT
D_IN
SCLK
RD/WR
CS
The AD7816, AD7817, and AD7818 have a flexible serial
interface 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.
The AD7817 is available in a narrow body 0.15" 16-lead small
outline IC (SOIC), in a 16-lead, thin shrink small outline pack-
age (TSSOP), while the AD7816/AD7818 come in an 8-lead
small outline IC (SOIC) and an 8-lead microsmall outline IC
(MSOP).
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.
2. An overtemperature indicator is implemented by carrying out a
digital comparison of the ADC code for Channel 0 (tempera-
ture sensor) with the contents of the on-chip overtemperature
register. The overtemperature 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.
REV. C
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