July 1995
À Ó
LM12434/LM12 L 438 12-Bit
a
Sign Data Acquisition
System with Serial I/O and Self-Calibration
General Description
The LM12434 and LM12 L 438 are highly integrated Data
Acquisition Systems. Operating on 3V to 5V, they combine a
fully-differential self-calibrating (correcting linearity and zero
Key Specifications
f
e
Resolution
À
8 MHz L, f
e
CLK
Ó
6 MHz
12-bit
À
Ó
CLK
Y
Y
Y
Y
a
a
Ó
Ó
sign or 8-bit
À
sign
13-bit conversion time
9-bit conversion time
13-bit Through-put rate
5.5 ms 7.3 ms (max)
2.6 ms 3.5 ms (max)
À
a
errors) 13-bit (12-bit
sign) analog-to-digital converter
(ADC) and sample-and-hold (S/H) with extensive analog
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
instruction RAM can store the conversion sequence for up
to eight acquisitions through the LM12 L 438’s eight-input
multiplexer. The LM12434 has a four-channel multiplexer, a
differential multiplexer output, and a differential S/H input.
À
Ó
140k samples/s 105k sample/s (min)
Comparison time (‘‘watchdog’’ mode)
1.4 ms 1.8 ms (max)
Y
À
Ó
Y
Y
Y
Y
Y
À Ó
Serial Clock
Integral Linearity Error
10 MHz 6 MHz (max)
g
1 LSB (max)
a
À
Ó
V
IN
range
GND to V
A
À Ó
45 mW 20 mW (max)
Power dissipation
Stand-by mode
À
Ó
The LM12434 and LM12 L 438 can also operate with 8-bit
sign resolution and in a supervisory ‘‘watchdog’’ mode
À Ó
25 mW 16.5 mW (typ)
power dissipation
Supply voltage LM12L438
LM12434/8
a
Y
g
3.3V 10%
that compares an input signal against two programmable
limits.
g
5V 10%
Features
Three operating modes: 12-bit
Acquisition times and conversion rates are programmable
through the use of internal clock-driven timers. The differen-
tial reference voltage inputs can be externally driven for ab-
solute or ratiometric operation.
Y
a
a
sign,
sign, 8-bit
and ‘‘watchdog’’ comparison mode
Single-ended or differential inputs
Built-in Sample-and-Hold
Y
Y
Y
Y
All registers, RAM, and FIFO are directly accessible through
the high speed and flexible serial I/O interface bus. The
serial interface bus is user selectable to interface with the
following protocols with zero glue logic: MICROWIRE/
PLUSTM, Motorola’s SPI/QSPI, Hitachi’s SCI, 8051 Family’s
2
Serial Port (Mode 0), I C and the TMS320 Family’s Serial
Port.
Instruction RAM and event sequencer
Ó
À
8-channel (LM12 L 438) or 4-channel (LM12434)
multiplexer
32-word conversion FIFO
Y
Y
Y
Y
Y
Programmable acquisition times and conversion rates
Self-calibration and diagnostic mode
Power down output for system power management
Read while convert capability for maximum through-put
rate
An evaluation kit for demonstrating the LM12434 and
À
Ó
LM12 L 438 is available.
TRI-STATEÉ is a registered trademark of National Semiconductor Corporation.
MICROWIRE/PLUSTM is a trademark of National Semiconductor Corporation.
WindowsÉ is a registered trademark of Microsoft Corporation.
Applications
Data Logging
Y
Y
Portable Instrumentation
Process Control
Y
Y
Energy Management
Robotics
Y
Connection Diagrams
28-Pin PLCC Package
28-Pin Wide Body SO Package
TL/H/11879–1
TL/H/11879–2
Order Number LM12434CIWM, LM12438CIWM, or
LM12L438CIWM
See NS Package Number M28B
*Pin names in ( ) apply to the LM12434
Order Number LM12434CIV, LM12438CIV, or
LM12L438CIV
See NS Package Number V28A
C
1995 National Semiconductor Corporation
TL/H/11879
RRD-B30M85/Printed in U. S. A.