AD7798 Datasheet, PDF (1/28 Pages) Analog Devices – Low Power, 24-Bit/16-Bit Sigma-Delta ADC with In-Amp

Data Sheet
3-Channel, Low Noise, Low Power,
16-/24-Bit, Σ-Δ ADC with On-Chip In-Amp
AD7798/AD7799
FEATURES
RMS noise:
27 nV at 4.17 Hz (AD7799)
65 nV at 16.7 Hz (AD7799)
40 nV at 4.17 Hz (AD7798)
85 nV at 16.7 Hz (AD7798)
Current: 380 µA typical
Power-down: 1 µA maximum
Low noise, programmable gain, instrumentation amp
Update rate: 4.17 Hz to 470 Hz
3 differential inputs
Internal clock oscillator
Simultaneous 50 Hz/60 Hz rejection
Reference detect
Low-side power switch
Programmable digital outputs
Burnout currents
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
APPLICATIONS
Weigh scales
Pressure measurement
Strain gauge transducers
Gas analysis
Industrial process control
Instrumentation
Portable instrumentation
Blood analysis
Smart transmitters
Liquid/gas chromotography
6-digit DVM
FUNCTIONAL BLOCK DIAGRAM
GND AV_DD
REFIN(+) REFIN(–)
AD7798/AD7799
REFERENCE
DETECT
AIN1(+)
AIN1(–)
AIN2(+)
AIN2(–)
AIN3(+)/P1
AIN3(–)/P2
PSW
AV_DD
MUX
IN-AMP
Σ-Δ
ADC
GND
GND
INTERNAL
CLOCK
Figure 1.
SERIAL
INTERFACE
AND
CONTROL
LOGIC
AD7798: 16-BIT
AD7799: 24-BIT
DOUT/RDY
DIN
SCLK
CS
DV_DD
GENERAL DESCRIPTION
The AD7798/AD7799 are low power, low noise, complete
analog front ends for high precision measurement applications.
The AD7798/AD7799 contains a low noise, 16-/24-bit ∑-∆
ADC with three differential analog inputs. The on-chip, low
noise instrumentation amplifier means that signals of small
amplitude can be interfaced directly to the ADC. With a gain
setting of 64, the rms noise is 27 nV for the AD7799 and 40 nV
for the AD7798 when the update rate equals 4.17 Hz.
On-chip features include a low-side power switch, reference
detect, programmable digital output pins, burnout currents,
and an internal clock oscillator. The output data rate from the
part is software-programmable and can be varied from 4.17 Hz
to 470 Hz.
The part operates with a power supply from 2.7 V to 5.25 V.
The AD7798 consumes a current of 300 µA typical, whereas the
AD7799 consumes 380 µA typical. Both devices are housed in a
16-lead TSSOP package.
Rev. B
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