LND494 Datasheet, PDF (1/6 Pages) Linear Dimensions Semiconductor – Pulse-Width-Modulation Control Circuits

DATA SHEET
LND494
Pulse-Width-Modulation Control Circuits
GENERAL DESCRIPTION
FEATURES
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
output transistors provide either common-emitter
NON INV INPUT
or emitter-follower output capability. Each
device provides for push-pull or single-ended
INV INPUT
output op_`eration, which may be selected through
the output-control function. The architecture of
these devices prohibits the possibility of either
FEEDBACK
output being pulsed twice during push-pull
operation.
DEAD-TIME CONTROL
• 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
Error
Amp1
2
16 NON INV INPUT
15 INV INPUT
Error
Amp2
3
14 REF OUT
4
13 OUTPUT CONTROL
CT
5
12 Vcc
RT
6
11 C2
GND 7
10 E2
C1 8
9 E1
• Linear Dmensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel [phone] • fax [phone] • www.lineardimensions.com •