AD7782 Datasheet, PDF (1/12 Pages) Analog Devices – Read Only, Pin Configured 24-Bit ADC

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FEATURES
2-Channel, 24-Bit ⌺-⌬ ADC
Pin Configurable (No Programmable Registers)
Pin Selectable Input Channels
Pin Programmable Input Ranges (؎2.56 V or ؎160 mV)
Fixed 19.79 Hz Update Rate
Simultaneous 50 Hz and 60 Hz Rejection
24-Bit No Missing Codes
18.5-Bit p-p Resolution (؎2.56 V Range)
16.5-Bit p-p Resolution (؎160 mV Range)
INTERFACE
Master or Slave Mode of Operation
Slave Mode
3-Wire Serial
SPI™, QSPI™, MICROWIRE™, and DSP-Compatible
Schmitt Trigger on SCLK
POWER
Specified for Single 3 V and 5 V Operation
Normal: 1.3 mA @ 3 V
Power-Down: 9 ␮A
ON-CHIP FUNCTIONS
Rail-Rail Input Buffer and PGA
APPLICATIONS
Sensor Measurement
Industrial Process Control
Temperature Measurement
Pressure Measurements
Weigh Scales
Portable Instrumentation
Read Only, Pin Configured
24-Bit ⌺-⌬ ADC
AD7782
FUNCTIONAL BLOCK DIAGRAM
V_DD
GND
REFIN(+) REFIN(–) XTAL1 XTAL2
AD7782
OSCILLATOR
AND
PLL
AIN1(+)
AIN1(–)
AIN2(+)
AIN2(–)
MUX
BUF
PGA
24-BIT ⌺-⌬
ADC
SERIAL
INTERFACE
AND
CONTROL
LOGIC
DOUT/RDY
SCLK
MODE
CS
CH1/CH2
RANGE
BASIC CONNECTION DIAGRAM
ANALOG
INPUT
ANALOG
INPUT
REFERENCE
INPUT
POWER SUPPLY
V_DD
AD7782
AIN1(+)
AIN1(–)
AIN2(+)
AIN2(–)
REFIN(+)
REFIN(–)
CS
DOUT/RDY
SCLK
XTAL1
XTAL2
GND
DIGITAL
INTERFACE
32.768kHz
CRYSTAL
GENERAL DESCRIPTION
The AD7782 is a complete analog front end for low-frequency
measurement applications. The 24-bit sigma-delta ADC contains
two fully differential analog input channels that can be config-
ured with a gain of 1 or 16 allowing full-scale input signal ranges
of ± 2.56 V or ± 160 mV from a +2.5 V differential reference
input.
The AD7782 has an extremely simple, read-only digital interface
which can be operated in master mode or slave mode. There are
no on-chip registers to be programmed. The input signal range
and input channel selection are configured using two external pins.
The device operates from a 32.768 kHz crystal with an on-chip PLL
generating the required internal operating frequency. The output
data rate from the part is fixed via the master clock at 19.79 Hz and
provides simultaneous 50 Hz and 60 Hz rejection at this update
rate. Eighteen-bit p-p resolution can be obtained at this update rate.
The part operates from a single 3 V or 5 V supply. When operating
from 3 V supplies, the power dissipation for the part is 3.9 mW.
The AD7782 is available in a 16-lead TSSOP package.
Another part in the AD778x family is the AD7783. It is similar
to the AD7782 except it has two integrated current sources and
only one differential input channel.
SPI and QSPI are trademarks of Motorola Inc.
MICROWIRE is a trademark of National Semiconductor Corporation.
REV. 0
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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.
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© Analog Devices, Inc., 2001