
SG2525A
SG3525A
REGULATING PULSE WIDTH MODULATORS
5.1V REFERENCETRIMMED TO
±
1%
.
100Hz TO 500KHz OSCILLATORRANGE
.
SEPARATEOSCILLATORSYNCTERMINAL
.
ADJUSTABLE DEADTIMECONTROL
.
INTERNALSOFT-START
.
PULSE-BY-PULSESHUTDOWN
.
INPUT UNDERVOLTAGE LOCKOUT WITH
HYSTERESIS
.
LATCHING PWM TO PREVENT MULTIPLE
PULSES
.
DUAL SOURCE/SINKOUTPUT DRIVERS
DESCRIPTION
The SG3525Aseriesof pulsewidthmodulatorinte-
grated circuits are designed to offer improved per-
formance and lowered external parts count when
used indesigningall typesof switchingpower sup-
plies. Theon-chip+ 5.1 V referenceistrimmedto
±
1 %andthe inputcommon-moderangeof theerror
amplifier includesthe referencevoltageeliminating
externalresistors. A sync input to the oscillator al-
lowsmultipleunitsto beslavedorasingleunittobe
synchronizedto an externalsystem clock. A single
resistorbetweentheC
T
andthedischargeterminals
provide a wide range of dead time ad-
justment.
Thesedevicesalsofeaturebuilt-insoft-startcircuitry
with only an external timing capacitor required. A
shutdownterminalcontrolsboththesoft-startcircu-
ity and the outputstages, providing instantaneous
.
8 TO 35 V OPERATION
turn off through the PWM latch with pulsed shut-
down,as wellassoft-startrecycle with longershut-
downcommands.Thesefunctionsarealsocontrol-
ledbyan undervoltagelockoutwhichkeepstheout-
puts off and the soft-start capacitor discharged for
sub-normal input voltages.This lockoutcircuitry in-
cludesapproximately500mVofhysteresisforjitter-
free operation. Another feature of thesePWM cir-
cuits is a latch following the comparator. Once a
PWM pulses has been terminated for any reason,
theoutputswill remainoffforthedurationof thepe-
riod. The latch is reset with each clock pulse. The
output stages are totem-pole designs capable of
sourcing or sinking in excess of 200 mA. The
SG3525AoutputstagefeaturesNORlogic,givinga
LOWoutputfor an OFF state.
DIP16
16(Narrow)
Type
Plastic DIP
SO16
SG2525A
SG2525AN
SG2525AP
SG3525A
SG3525AN
SG3525AP
PIN CONNECTIONS AND ORDERING NUMBERS
(top view)
June 2000
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