Datasheet
SG2525A/2527A
SG3525A/3527A
December 1995
REGULATING PULSE WIDTH MODULATORS
.8 TO 35 V OPERATION
.5.1 V REFERENCE TRIMMED TO ± 1%
.100 Hz TO 500 KHz OSCILLATOR RANGE
.SEPARATE OSCILLATORSYNC TERMINAL
.ADJUSTABLE DEADTIME CONTROL
.INTERNAL SOFT-START
.PULSE-BY-PULSESHUTDOWN
.INPUT UNDERVOLTAGE LOCKOUT WITH
HYSTERESIS
.LATCHING PWM TO PREVENT MULTIPLE
PULSES
.DUAL SOURCE/SINK OUTPUT DRIVERS
DESCRIPTION
The SG3525A/3527Aseries ofpulsewidth modula-
torintegratedcircuits aredesignedto offerimproved
performanceandloweredexternalpartscountwhen
used in designing all types of switching power sup-
plies. 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 al-
lows multiple units to be slaved or a single unit to be
synchronizedto an external system clock. A single
resistorbetweentheC
T
andthedischarge terminals
provide a wide range of dead time ad- justment.
Thesedevices also featurebuilt-in soft-startcircuitry
with only an external timing capacitor required. A
shutdownterminal controls both thesoft-start circu-
ity and the output stages, providing instantaneous
turn off through the PWM latch with pulsed shut-
down, as well as soft-start recycle with longer shut-
down commands. These functionsare also control-
led by an undervoltagelockoutwhich keeps theout-
puts off and the soft-start capacitor discharged for
sub-normal input voltages. This lockout circuitry in-
cludesapproximately500mV of hysteresisforjitter-
free operation. Another feature of these PWM cir-
cuits is a latch following the comparator. Once a
PWM pulses has been terminated for any reason,
the outputswill remain off for the durationof the pe-
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
SG3525Aoutputstage features NOR logic, giving a
LOW outputfor anOFF state.The SG3527Autilizes
OR logic which results in a HIGH output level when
OFF.
DIP16 16(Narrow)
Type Plastic DIP SO16
SG2525A SG2525AN SG2525AP
SG2527A SG2527AN SG2527AP
SG3525A SG3525AN SG3525AP
SG3527A SG3527AN SG3527AP
PIN CONNECTIONS AND ORDERING NUMBERS (top view)
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