LM12454/LM12458/LM12H458
12-Bit + Sign Data Acquisition System with
Self-Calibration
General Description
The LM12458, and LM12H458 are highly integrated Data
Acquisition Systems. Operating on just 5V, they combine a
fully-differential self-calibrating (correcting linearity 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 consecutive conversions,
using two’s 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)458’s eight-input multiplexer.
The obsolete LM12454 has a four-channel multiplexer,
a differential multiplexer output, and a differential S/H
input. The LM12(H)458 can also operate with 8-bit + sign
resolution and in a supervisory “watchdog” mode that compares
an input signal against two programmable 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 absolute
or ratiometric operation or can be derived using the
internal 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 data bus. The LM12(H)458 includes a direct
memory access (DMA) interface for high-speed conversion
data transfer.
Additional applications information can be found in applications
notes AN-906, AN-947 and AN-949.