12-bit Sign Data Acquisition System With Self-calibration - National Semiconductor

The LM12454 LM12458 and LM12H458 are highly inte- grated Data Acquisition Systems. Operating on just 5V, they combine a fully-differential self-calibrating (correcting linear- ity and zero errors) 13-bit (12-bit + sign) Analog-to-digital converter (ADC) and sample-and-hold (S/H) with extensive Analog functions and digital functionality. Up to 32 consecu- tive conversions, using twos complement format, CAN be stored in an internal 32-word (16-bit wide) FIFO data Buffer An internal 8-word RAM CAN store the conversion sequence for up to eight acquisitions through the LM12(H)458s eight-input multiplexer. The LM12454 has a four-channel multiplexer, a differential multiplexer output, and a differential S/H input. The LM12454 and LM12(H)458 CAN also operate with 8-bit + sign resolution and in a supervisory watchdog mode that compares an input signal against two program- mable limits. Programmable acquisition times and conversion rates are possible through the use of internal clock-driven Timers The reference voltage input CAN be externally generated for ab- solute or ratiometric operation or CAN be derived using the in- ternal 2.5V bandgap reference. All Registers RAM, and FIFO are directly addressable through the high speed Microprocessor Interface to either an 8-bit or 16-bit databus. The LM12454 and LM12(H)458 in- clude a direct memory access (DMA) Interface for high-speed conversion data transfer. By National Semiconductor Corporation