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AD7783
Read-Only, Pin Configured 24-Bit ⌺-⌬ ADC
with Excitation Current Sources
FEATURES
Single-Channel, 24-Bit ⌺ -⌬ ADC
Pin Configurable (No Programmable Registers)
ISOURCE Select
™
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-to-Rail Input Buffer and PGA
APPLICATIONS
Sensor Measurement
Industrial Process Control
Temperature Measurement
Pressure Measurement
Weigh Scales
Portable Instrumentation
GENERAL DESCRIPTION
The AD7783 is a complete analog front end for low frequency
measurement applications. The 24-bit sigma-delta ADC con-
tains one fully differential input channel that can be configured
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.
It also contains two 200 mA integrated current sources.
The AD7783 has an extremely simple, read-only digital inter-
face that can be operated in master mode or slave mode.
There are no on-chip registers to be programmed. The input
signal range and current source selection are configured using
two external pins.
FUNCTIONAL BLOCK DIAGRAM
OSCILLATOR
AND
PLL
DOUT/RDY
SCLK
MODE
XTAL1
XTAL2
SERIAL
INTERFACE
AND
CONTROL
LOGIC
CS
REFIN(–)
REFIN(+)
24-BIT ⌺-⌬
ADC
RANGE
AD7783
V
DD
GND
BUF
PGA
MUX
AIN(+)
AIN(–)
IOUT1
V
DD
IEXC1
200A
IEXC2
200A
IOUT2
IPIN
BASIC CONNECTION DIAGRAM
AD7783
REFIN(+)
REFIN(–)
AIN(–)
AIN(+)
IOUT2
IOUT1
XTAL1
V
DD
DOUT/RDY
CS
SCLK
XTAL2
GND
REFERENCE
INPUT
CURRENT
SOURCES
ANALOG
INPUT
POWER SUPPLY
32.768kHz
CRYSTAL
DIGITAL
INTERFACE
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. At this update rate, 18-bit p-p resolution can
be obtained.
The part operates from a single 3 V or 5 V supply. When oper-
ating from 3 V supplies, the power dissipation for the part is
3.9 mW. The AD7783 is available in a 16-lead TSSOP.
Another part in the AD778x family is the AD7782. It is similar
to the AD7783 except it has no integrated current sources and
two differential input channels.
