UC1527B Datasheet | Unitrode

UC3527B Not Remended For New Designs Regulating Pulse Width Modulators application INFO available UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B Features - 8 to 35V Operation - 5.1V Buried Zener Reference Trimmed to ±0.75% - 100Hz to 500k Hz 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 - Low Cross Conduction Output Stage - Tighter Reference Specifications BLOCK DIAGRAM DESCRIPTION The UC1525B/1527B series of pulse width modulator integrated circuits are designed to offer improved performance and lowered external parts count when used in designing all types of switching power supplies. The on-chip +5.1V buried zener reference is trimmed to ±0.75% and the input mon-mode range of the error amplifier includes the reference voltage, eliminating external resistors. A sync input to the oscillator allows multiple units to be slaved or a single unit to be synchronized to an external system clock. A single resistor between the CT and the discharge terminals provide a wide range of dead time adjustment. These devices also feature built-in soft-start circuitry with only an external timing capacitor required. 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 mands. These functions are also controlled by an undervoltage lockout which keeps the outputs off and the soft-start capacitor discharged for sub-normal input voltages. This lockout circuitry includes approximately 500m V of hysteresis for jitter-free operation. Another feature of these PWM circuits is a latch following the parator. Once a PWM pulse has been terminated for any reason, the outputs will remain off for the duration of the period. The...