The ADS7870 (US patents 6140872, 6060874) is a complete low-power data acquisition system on a single chip. It consists of a 4-channel differential/8-channel single-ended multiplexer, precision programmable gain amplifier, 12-bit successive approximation analog-to-digital (A/D) converter, and a precision voltage reference.
The programmable-gain amplifier provides high input impedance, excellent gain accuracy, good common-mode rejection, and low noise.
For many low-level signals, no external amplification or impedance buffering is needed between the signal source and the A/D input.
The offset voltage of the PGA is auto zeroed. Gains of 1, 2, 4, 5, 8, 10, 16, and 20 V/V allow signals as low as 125 mV to produce full-scale digital outputs.
The ADS7870 contains an internal reference, which is trimmed for high initial accuracy and stability vs temperature. Drift is typically 10 ppm/°C. An external reference can be used in situations where multiple ADS7870s share a common reference.
The serial interface allows the use of SPI, QSPI, Microwire, and 8051-family protocols, without glue logic.