DATA SHEET
LND494
Pulse-Width-Modulation Control Circuits
GENERAL DESCRIPTION
The LND494 incorporate on a single monolithic
chip all the functions required in the construction
of a pulse-width-modulation control circuit.
Designed primarily for power supply control,
these devices offer the systems engineer the
flexibility to tailor the power supply control
circuitry to his application. The LND494
contains an error amplifier, an on-chip
adjustable oscillator, a dead time control
comparator, pulse –steering control flip-flop, a 5-
volt, 5% precision regulator, and output-control
circuits. The error amplifier exhibits a common-
mode voltage range from –0.3 volts to Vcc-2
volts. The dead-time control compactor has a
fixed offset that provides approximately 5% dead
time when externally altered. The on-chip
oscillator may be by passed by terminating R
T
(pin 6) to the reference output and providing a
sawtooth input to C
T
(pin 5), or it may be used to
drive the common circuits in synchronous
multiple-rail power supplies. The uncommitted
NON INV INPUT
output transistors provide either common-emitter
or emitter-follower output capability. Each
INV INPUT
device provides for push-pull or single-ended
output operation, which may be selected through
`
the output-control function. The architecture of
FEEDBACK
these devices prohibits the possibility of either
output being pulsed twice during push-pull
DEAD-TIME CONTROL
operation.
C
T
R
T
GND
C1
FEATURES
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Complete PWM Circuitry Power Control
Uncommitted Outputs for 200mA Sink
or source current
Output Control Selects Single-Ended or
Push-Pull operation
Internal Circuitry Prohibits Double
Pulse at Either Output
Variable Dead-Time Provides a stable
5-V Reference Supply, 5%
Circuit Architecture Allows Easy
Synchronization
LND494
(Top View)
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
NON INV INPUT
INV INPUT
REF OUT
OUTPUT CONTROL
Vcc
C2
E2
E1
Error
Amp1
Error
Amp2
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Linear Dmensions, Inc.
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445 East Ohio Street, Chicago IL 60611 USA
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tel 312.321.1810
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fax 312.321.1830
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LINEAR_DIMENSIONS [ LINEAR DIMENSIONS SEMICONDUCTOR ]
