3-Channel, Low Noise, Low Power, 16-/24-Bit
∑-Δ ADC with On-Chip In-Amp and Reference
AD7792/AD7793
FEATURES
FUNCTIONAL BLOCK DIAGRAM
GND
AV
REFIN(+)/AIN3(+) REFIN(–)/AIN3(–)
DD
Up to 23 bits effective resolution
RMS noise
40 nV @ 4.17 Hz
85 nV @ 16.7 Hz
V
BIAS
BAND GAP
REFERENCE
GND
AV
DD
Current: 400 μA typical
AIN1(+)
AIN1(–)
AIN2(+)
AIN2(–)
DOUT/RDY
DIN
SERIAL
INTERFACE
AND
MUX
Power-down: 1 μA maximum
Low noise programmable gain instrumentation amp
Band gap reference with 4 ppm/°C drift typical
Update rate: 4.17 Hz to 470 Hz
3 differential inputs
Σ-Δ
ADC
BUF
IN-AMP
SCLK
CS
CONTROL
LOGIC
AV
DD
GND
DV
DD
IOUT1
IOUT2
INTERNAL
CLOCK
AD7792: 16-BIT
AD7793: 24-BIT
Internal clock oscillator
CLK
Figure 1.
Simultaneous 50 Hz/60 Hz rejection
Programmable current sources
On-chip bias voltage generator
Burnout currents
GENERAL DESCRIPTION
The AD7792/AD7793 are low power, low noise, complete
analog front ends for high precision measurement applications.
The AD7792/AD7793 contain a low noise 16-/24-bit ∑-Δ ADC
with three differential analog inputs. The on-chip, low noise
instrumentation amplifier means that signals of small ampli-
tude can be interfaced directly to the ADC. With a gain
setting of 64, the rms noise is 40 nV when the update rate
equals 4.17 Hz.
Power supply: 2.7 V to 5.25 V
–40°C to +105°C temperature range
Independent interface power supply
16-lead TSSOP package
Interface
3-wire serial
SPI®, QSPI™, MICROWIRE™, and DSP compatible
Schmitt trigger on SCLK
The devices contain a precision low noise, low drift internal
band gap reference and can accept an external differential
reference. Other on-chip features include programmable
excitation current sources, burnout currents, and a bias voltage
generator. The bias voltage generator sets the common-mode
voltage of a channel to AVDD/2.
APPLICATIONS
Thermocouple measurements
RTD measurements
Thermistor measurements
Gas analysis
The devices can be operated with either the internal clock or an
external clock. The output data rate from the parts is software-
programmable and can be varied from 4.17 Hz to 470 Hz.
Industrial process control
Instrumentation
Portable instrumentation
Blood analysis
Smart transmitters
Liquid/gas chromatography
6-digit DVM
The parts operate with a power supply from 2.7 V to 5.25 V.
They consume a current of 400 μA typical and are housed in a
16-lead TSSOP package.
Rev. B
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