REGULATING PWM IC

DESCRIPTION

The UTC U3525U is a pulse width modulator IC and designed

for switching power supplies application to improve performance

and reduce external parts usage.

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. The output stage features NOR logic, giving

a LOW output for an OFF state. An under-voltage lockout circuitry,

which keeps the outputs off and the soft-start capacitor discharged

for sub-normal input voltages, includes approximately 500 mV of

hysteresis for jitter free operation. The PWM circuits also feature a

latch following the comparator. When a PWM pulses has been

terminated, the outputs will remain off for the duration of the period.

The latch is reset with each clock pulse. The output stages are

totem-pole designs capable of sourcing or sinking in excess of

200mA.

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FEATURES

* Input Voltage: 8~35V

* On-chip +5.1V reference is trimmed to ±1%

* 100HZ ~ 400KHZ oscillator range

* Separate oscillator sync terminal

* Adjustable dead time control

* Internal soft-start

* Pulse-by-pulse shutdown

* Input under-voltage lockout with hysteresis

* Latching PWM to prevent multiple pulses

* Dual source/sink output drivers