LM12454_06 Datasheet, PDF (1/36 Pages) National Semiconductor (TI) – 12-Bit + Sign Data Acquisition System with Self-Calibration

February 2006
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 con-
versions, using two’s complement format, can be stored in
an internal 32-word (16-bit wide) FIFO data buffer. An inter-
nal 8-word RAM can store the conversion sequence for up to
eight acquisitions through the LM12(H)458’s eight-input mul-
tiplexer. The obsolete LM12454 has a four-channel multi-
plexer, 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 com-
pares 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 ab-
solute 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 applica-
tions notes AN-906, AN-947 and AN-949.
Key Specifications
(f_CLK = 5 MHz; 8 MHz, H)
j Resolution
12-bit + sign or 8-bit + sign
j 13-bit conversion time
8.8 µs, 5.5 µs (H) (max)
j 9-bit conversion time
4.2 µs, 2.6 µs (H) (max)
j 13-bit Through-put rate
88k samples/s (min),
140k samples/s (H) (min)
j Comparison time
(“watchdog” mode)
j ILE
j V_IN range
j Power Consumption
2.2 µs (max),
1.4 µs (H) (max)
±1 LSB (max)
GND to V_A+
30 mW, 34 mW (H) (max)
j Stand-by mode
50 µW (typ)
j Single supply
3V to 5.5V
Features
n Three operating modes: 12-bit + sign, 8-bit + sign, and
“watchdog”
n Single-ended or differential inputs
n Built-in Sample-and-Hold and 2.5V bandgap reference
n Instruction RAM and event sequencer
n 8-channel multiplexer
n 32-word conversion FIFO
n Programmable acquisition times and conversion rates
n Self-calibration and diagnostic mode
n 8- or 16-bit wide data bus microprocessor or DSP
interface
Applications
n Data Logging
n Instrumentation
n Process Control
n Energy Management
n Inertial Guidance
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