ML4828

May 1997 ML4828* BiCMOS Phase Modulation/Soft Switching Controller GENERAL DESCRIPTION The ML4828 is a complete BiCMOS phase modulation control IC suitable for full bridge soft switching converters. Unlike conventional PWM circuits, the phase modulation technique allows for zero voltage switching (ZVS) transitions and square wave drive across the transformer. The IC modulates the phases of the two sides of the bridge to control output power. The ML4828 can be operated in either voltage or current mode. Both cycle-by-cycle current limit, integrating fault detection, and soft start reset are provided. The undervoltage lockout circuit features a 1.5V hysteresis with a low starting current to allow off-line start up with a bleed resistor. A shutdown function powers down the IC, putting it into a low quiescent state. The circuit can be operated at frequencies up to 1MHz. The ML4828 contains four high current CMOS outputs which feature high slew rate with low cross conduction. FEATURES s s s s s s s 5V BiCMOS for low power and high frequency (1MHz) operation Full bridge phase modulation zero voltage switching circuit with independent programmable delay times Current or voltage mode operation capability Cycle-by-cycle current limiting with integrating fault detection and restart delay Can be externally synchronized Four 3Ω CMOS output drivers Under-voltage lockout circuit with 1.5V hysteresis *Some Packages Are End Of Life BLOCK DIAGRAM VCC 14 VREF 5 SYNC RT 6 3 CT 4 2.5V REF ...