UC1572,UC2572,UC3572,pdf(Negat

The UC3572 is a negaTIve output flyback pulse width modulator which converts a posiTIve input voltage to a regulated negaTIve output voltage. The chip is opTImized for use in a single inductor negative flyback switching converter employing an external PMOS switch. The block diagram consists of a precision reference, an error amplifier configured for voltage mode operation, an oscillator, a PWM comparator with latching logic, and a 0.5A peak gate driver. The UC3572 includes an undervoltage lockout circuit to insure sufficient input supply voltage is present before any switching activity can occur, and a pulse-by-pulse current limit. Output current can be sensed and limited to a user determined maximum value.