UC1572
UC2572
UC3572 Negative Output Flyback Pulse Width Modulator
FEATURES DESCRIPTION Simple Single Inductor Flyback PWM
for Negative Voltage Generation 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 50ВµA, making the UC3572 ideal for battery
powered applications. Drives External PMOS Switch Contains UVLO Circuit Includes Pulse-by-Pulse Current Limit Low 50ВµA Sleep Mode Current BLOCK DIAGRAM UDG-94094-2 SLUS275A -MARCH 1999 -REVISED AUGUST 2001 UC1572
UC2572
UC3572
ABSOLUTE MAXIMUM RATINGS CONNECTION DIAGRAM VCC . 35V
EAINV -0.6V to VCC
IEAOUT 25mA
RAMP -0.3V to 4V
CS . -0.3V to VCC
Iout -0.7A to 0.7A
I3VREF . -15mA …
