Single-Chip Data Acquisition System

Burr-Brown Corporation a low-power data acquisition system (DAS) on a single chip offers complete signal conditioning and conversion for industrial process control, medical, scientific, and communications applications. It also meets the requirements of consumer markets such as multi-sensor monitoring in sports activities and virtual reality systems. The system is targeted for portable and battery-powered systems, low power control systems, multi-channel sensor signal acquisition, smart sensor signal conditioning, and general purpose instrumentation where delta-sigma products are too slow. The system's low power is suited for portable and battery-powered systems, which need to digitize a number of signals. Because this device handles a range of input voltages, it is also suited for monitoring key voltages in control systems. In addition, its versatility allows for routine monitoring of important signals in multi-channel or multi-function systems.

The system consists of a four-channel differential/eight-channel single-ended multiplexer (MUX), precision programmable gain instrumentation amplifier (PGIA), 12-bit successive approximation analog-to-digital converter (ADC) and an accurate on-chip voltage reference. The programmable-gain amplifier provides high input impedance, good 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, offering excellent long term dc stability. Gains of 1, 2, 4, 5, 8, 10, 16 and 20V/V provide 16-bit dynamic range and allow signals as low as 125 mV to produce full scale digital outputs. It contains an internal reference, which is trimmed for high initial accuracy and stability vs temperature. Drift is typically 10 ppm/°Celsius. An external reference can be used in situations where multiple ADS7870s share a common reference. The systemincludes a four-bit digital I/O addressed through the serial interface. This provides additional versatility for control of external multiplexers or other ancillary functions. The serial interface allows the use of SPI, QSPI, Microwire, and 8051-family protocols, without glue logic, and can be electrically isolated with inexpensive opto-couplers.

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