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SLUS191C – FEBRUARY 1997 – REVISED JANUARY 2008
REGULATING PULSE WIDTH MODULATORS
1
FEATURES
8-V to 35-V Operation
5.1-V Reference Trimmed to 1%
100-Hz to 500-kHz Oscillator Range
Separate Oscillator Sync Terminal
Adjustable Deadtime Control
Internal Soft-Start
Pulse-by-Pulse Shutdown
Input Undervoltage Lockout With Hysteresis
Latching PWM to Prevent Multiple Pulses
Dual Source/Sink Output Drivers
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DESCRIPTION
The UC1525A/1527A series of pulse width modulator
integrated circuits are designed to offer improved
performance and lowered external parts count when
used in designing all types of switching power
supplies. The on-chip +5.1-V reference is trimmed to
1% and the input common-mode range of the error
amplifier includes the reference voltage, eliminating
external resistors. A sync input to the oscillator allows
multiple units to be slaved or a single unit to be
synchronized to an external system clock. A single
resistor between the C
T
and the discharge terminals
provides a wide range of dead-time adjustment.
These devices also feature built-in soft-start circuitry
with only an external timing capacitor required. A
shutdown terminal controls both the soft-start circuitry
and the output stages, providing instantaneous turn
off through the PWM latch with pulsed shutdown, as
well as soft-start recycle with longer shutdown
commands.
BLOCK DIAGRAM
VREF
16
OSC
OUT
4
13
Reference
Regulator
To Internal
Circutry
Flip
Flop
NOR
14
OUTPUT B
UVLO
Lockout
NOR
11
OUTPUT A
VC
+VIN
15
GROUND 12
SYNC
RT
CT
3
6
OSC
5
DISCHARGE 7
UC1525A
Output Stage
13
COMP
COMPENSATION 9
INV INPUT 1
NI INPUT 2
SOFTSTART 8
3 kW
SHUTDOWN 10
OR
14
OUTPUT B
Error
Amp
VREF
50
m
A
R
S
S
PWM
Latch
OR
11
OUTPUT A
VC
5 kW
UC1527A
Output Stage
1
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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1997–2008, Texas Instruments Incorporated
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