CMOS, 24-Bit Sigma-Delta, Signal Conditioning ADC with RTD Current Source
The part features two differential analog inputs and a differential reference input. Normally, one of the channels will be used as the main channel with the second channel used as an auxiliary input to periodically measure a second voltage. It can be operated from a single supply (by tying the VSS pin to AGND) provided that the input signals on the analog inputs are more positive than -30 mV. By taking the VSS pin negative, the part can convert signals down to -VREF on its inputs. The part also provides a 400 µA current source that can be used to provide excitation for RTD transducers. The AD7711A thus performs all signal conditioning and conversion for a single or dual channel system.
The AD7711A is ideal for use in smart, microcontroller based systems. Input channel selection, gain settings and signal polarity can be configured in software using the bidirectional serial port. The AD7711A contains self-calibration, system calibration and background calibration options and also allows the user to read and write the on-chip calibration registers.
CMOS construction ensures low power dissipation, and a software programmable power-down mode reduces the standby power consumption to only 7 mW typical. The part is available in a 24-pin, 0.3 inch-wide, hermetic dual-in-line package (Cerdip) as well as a 24-lead small outline (SOIC) package.