The SG3525A, SG3527A pulse width modulator control circuits offer
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. These devices also feature 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 while the SG3527A utilized OR logic which gives a
high output when off.
? 8.0 V to 35 V Operation
? 5.1 V ± 1.0% Trimmed Reference
? 100 Hz to 400 kHz Oscillator Range
? Separate Oscillator Sync Pin
? Adjustable Deadtime Control
? Input Undervoltage Lockout
? Latching PWM to Prevent Multiple Pulses
? Pulse–by–Pulse Shutdown
? Dual Source/Sink Outputs: ±400 mA Peak