UC3527B
Not Recommended For New Designs
application
INFO
available UC1525B UC1527B
UC2525B UC2527B
UC3525B UC3527B Regulating Pulse Width Modulators
FEATURES DESCRIPTION 8 to 35V Operation 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 В±0.75% and the input
common-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 commands. 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 500mV of hysteresis for
jitter-free operation. Another feature of these PWM circuits is a latch following the comparator. Once a PWM pulse has been terminated for any reason, 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. The UC1525B output
stage features NOR logic, giving a LOW output for an OFF state. The …
