®
SG2525A
SG3525A
REGULATING PULSE WIDTH MODULATORS
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8 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
DIP16
16(Narrow)
DESCRIPTION
The SG3525Aseries of pulse width modulator inte-
grated circuits are designed to offer improved per-
formance and lowered external parts count when
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
synchronized to an external system clock. A single
resistor betweenthe C
T
andthe dischargeterminals
provide a wide range of dead time ad- justment.
Thesedevicesalso featurebuilt-insoft-startcircuitry
with only an external timing capacitor required. A
shutdownterminal controls both the soft-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 functions are also control-
led by an undervoltagelockoutwhich keepsthe out-
puts off and the soft-start capacitor discharged for
sub-normal input voltages. This lockout circuitry in-
cludesapproximately 500 mV of hysteresisfor jitter-
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 outputs will remain off for the duration of 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 output for an OFF state.
PIN CONNECTIONS AND ORDERING NUMBERS
(top view)
Type
SG2525A
SG3525A
Plastic DIP
SG2525AN
SG3525AN
SO16
SG2525AP
SG3525AP
June 2000
1/12
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