Read-Only, Pin Configured 24-Bit ⌺-⌬ ADC
with Excitation Current Sources
AD7783
FEATURES
FUNCTIONAL BLOCK DIAGRAM
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
V
XTAL1 XTAL2
REFIN(+) REFIN(–)
GND
DD
V
DD
IEXC1
IEXC2
200A
200A
IOUT1
OSCILLATOR
AND
Simultaneous 50 Hz and 60 Hz Rejection
24-Bit No Missing Codes
PLL
IOUT2
IPIN
18.5-Bit p-p Resolution (±2.56 V Range)
DOUT/RDY
SCLK
SERIAL
INTERFACE
AND
CONTROL
LOGIC
16.5-Bit p-p Resolution (±160 mV Range)
AIN(+)
AIN(–)
24-BIT ⌺-⌬
ADC
MUX
BUF
PGA
INTERFACE
MODE
Master or Slave Mode of Operation
Slave Mode
CS
AD7783
3-Wire Serial
SPI®, QSPI™, MICROWIRE™, and DSP-Compatible
Schmitt Trigger on SCLK
RANGE
POWER
Specified for Single 3 V and 5 V Operation
Normal: 1.3 mA @ 3 V
Power-Down: 9 A
BASIC CONNECTION DIAGRAM
POWER SUPPLY
ON-CHIP FUNCTIONS
Rail-to-Rail Input Buffer and PGA
V
DD
AD7783
APPLICATIONS
AIN(+)
AIN(–)
ANALOG
INPUT
CS
Sensor Measurement
Industrial Process Control
Temperature Measurement
Pressure Measurement
Weigh Scales
DIGITAL
INTERFACE
DOUT/RDY
SCLK
IOUT1
IOUT2
CURRENT
SOURCES
XTAL1
32.768kHz
CRYSTAL
REFIN(+)
REFIN(–)
REFERENCE
INPUT
XTAL2
Portable Instrumentation
GND
GENERAL DESCRIPTION
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 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 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.
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.
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.
REV. C
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reliable. However, no responsibility is assumed by Analog Devices for its
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may result from its use. No license is granted by implication or otherwise
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2011
Fax:781/461-3113
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