
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-
recting 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
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.
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 LM12L458 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 = 6 MHz)
n
Resolution
12-bit + sign or 8-bit + sign
n
Single supply
+3V to +5.5V
n
13-bit conversion time
7.3 s
n
9-bit conversion time
3.5 s
n
13-bit Through-put rate
106k samples/s (min)
n
Comparison time (“watchdog” mode)
1.8 s (max)
n
ILE
±1 LSB (max)
n
Power Consumption
15 mW (max)
n
Stand-by mode
5 W (typ)
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
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
n
CMOS compatible I/O
Applications
n
Data Logging
n
Process Control
n
Energy Management
n
Medical Instrumentation
TRI-STATE is a registered trademark of National Semiconductor Corporation.
February 2006
LM12L458
12-Bit
+
Sign
Data
Acquisition
System
with
Self-Calibration
2006 National Semiconductor Corporation
DS011711
www.national.com