UC1525A, UC1527A
UC2525A, UC2527A
UC3525A, UC3527A
www.ti.com
SLUS191C–FEBRUARY 1997–REVISED JANUARY 2008
REGULATING PULSE WIDTH MODULATORS
1
FEATURES
DESCRIPTION
•
8-V to 35-V Operation
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•
•
•
•
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5.1-V Reference Trimmed to 1%
100-Hz to 500-kHz Oscillator Range
Separate Oscillator Sync Terminal
Adjustable Deadtime Control
Internal Soft-Start
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 CT 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.
Pulse-by-Pulse Shutdown
Input Undervoltage Lockout With Hysteresis
Latching PWM to Prevent Multiple Pulses
Dual Source/Sink Output Drivers
BLOCK DIAGRAM
OSC
OUT
VREF
16
4
13
11
VC
NOR
NOR
UVLO
Reference
Regulator
+VIN 15
Lockout
OUTPUT A
GROUND 12
To Internal
Circutry
SYNC
RT
3
6
5
7
Flip
Flop
OSC
14
OUTPUT B
CT
DISCHARGE
UC1525A
Output Stage
13
11
VC
R
COMP
S
OR
COMPENSATION 9
PWM
Latch
Error
Amp
V
OUTPUT A
REF
INV INPUT
NI INPUT
1
2
8
S
A
50 m
SOFTSTART
OR
3 kW
SHUTDOWN 10
14
OUTPUT B
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