Produktbeskrivning
Regulating Pulse-Width Modulator
The SG3525A pulse width modulator control circuit offers
improved performance and lower external parts count when
implemented for controlling all types of switching power supplies.
The on−chip +5.1 V reference is trimmed to 1% and the error
amplifier has an input common−mode voltage range that includes the
reference voltage, thus eliminating the need for external divider
resistors. A sync input to the oscillator enables multiple units to be
slaved or a single unit to be synchronized to an external system clock.
A wide range of deadtime can be programmed by a single resistor
connected between the CT and Discharge pins. This device also
features built−in soft−start circuitry, requiring only an external timing
capacitor. A shutdown pin 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 under voltage lockout inhibits the outputs
and the changing of the soft−start capacitor when VCC is below
nominal. The output stages are totem−pole design capable of sinking
and sourcing in excess of 200 mA. The output stage of the SG3525A
features NOR logic resulting in a low output for an off−state.