LM12454, LM12458, LM12H458
SNAS079A – MAY 2004 – REVISED FEBRUARY 2006
LM12454/LM12458/LM12H458 12-Bit + Sign Data Acquisition System with Self-Calibration
Check for Samples: LM12454, LM12458, LM12H458
Self-calibration and diagnostic mode
8- or 16-bit wide data bus microprocessor or
Three operating modes: 12-bit + sign, 8-bit +
sign, and “watchdog”
Single-ended or differential inputs
Built-in Sample-and-Hold and 2.5V bandgap
Instruction RAM and event sequencer
32-word conversion FIFO
Programmable acquisition times and
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.
Table 1. Key Specifications
(fCLK = 5 MHz; 8 MHz, H)
12-bit + sign or 8-bit + sign
13-bit conversion time
μs, 5.5 μs (H) (max)
9-bit conversion time
μs, 2.6 μs (H) (max)
13-bit Through-put rate
samples/s (H) (min)
μs (H) (max)
GND to VA
30 mW, 34 mW (H) (max)
3 to 5.5
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Products conform to specifications per the terms of the Texas
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