FEATURES
• Simple Single Inductor Flyback PWM
for Negative Voltage Generation
• Drives External PMOS Switch
• Contains UVLO Circuit
• Includes Pulse-by-Pulse Current Limit
• Low 50μA Sleep Mode Current

DESCRIPTION
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. The UVLO circuit turns the
chip off when the input voltage is below the UVLO threshold. In addition, a
sleep comparator interfaces to the UVLO circuit to turn the chip off. This reduces
the supply current to only 50μA, making the UC3572 ideal for battery
powered applications.