3-Channel, Low Noise, Low Power, 24-Bit, Sigma Delta ADC with On-Chip In-Amp

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 Σ-Δ 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.

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

* 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