July 1999
LM12L458
12-Bit + Sign Data Acquisition System with
Self-Calibration
General Description
The LM12L458 is a highly integrated 3.3V Data Acquisition
System. It combines a fully-differential self-calibrating (cor-
Key Specifications
=
(fCLK 6 MHz)
n Resolution
12-bit + sign or 8-bit + sign
7.3 µs
recting linearity and zero errors) 13-bit (12-bit
+ sign)
n 13-bit conversion time
n 9-bit conversion time
n 13-bit Through-put rate
analog-to-digital converter (ADC) and sample-and-hold
(S/H) with extensive analog functions and digital functional-
ity. Up to 32 consecutive conversions, using two’s comple-
ment 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 LM12L458’s eight-input multiplexer. The LM12L458 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.
3.5 µs
106k samples/s (min)
n Comparison time (“watchdog” mode)
n ILE
1.8 µs (max)
1 LSB (max)
GND to VA
±
+
n VIN range
n Power dissipation
n Stand-by mode
n Single supply
15 mW (max)
5 µW (typ)
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
n Instruction RAM and event sequencer
n 8-channel multiplexer
All registers, RAM, and FIFO are directly addressable
through the high speed microprocessor interface to either an
8-bit or 16-bit databus. The LM12L458 includes a direct
memory access (DMA) interface for high-speed conversion
data transfer.
n 32-word conversion FIFO
Applications
n Data Logging
n Process Control
n Energy Management
n Medical Instrumentation
n Programmable acquisition times and conversion rates
n Self-calibration and diagnostic mode
n 8- or 16-bit wide databus microprocessor or DSP
interface
n CMOS compatible I/O
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© 1999 National Semiconductor Corporation
DS011711
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