6534CV

® ISL6534 Data Sheet December 21, 2004 FN9134.1 Dual PWM with Linear The ISL6534 is a versatile triple regulator that has two independent synchronous-rectified buck controllers with integrated 12V gate drivers (OUT1 and OUT2) and a linear controller (OUT3) to offer precision regulation of up to three voltage rails. An optional shunt regulator allows 12V only operation, when a 5V supply is not available. Each controller has independent soft-start and enable functions combined on a single pin. A capacitor from each www.DataSheet4U.com SS/EN pin to ground sets the soft-start time, and pulling SS/EN below 1.0V disables the controller. The SS/EN pins can be controlled independently or they can be ganged together to provide complete control of start-up coordination. The PGOOD function indicates when all regulators have completed their soft start and provides an indication of shortcircuit conditions on either switching regulator. There are two ways to control the switching frequency of the PWM regulators. The default switching frequency is 300kHz (FS_SYNC pin open). A resistor from FS_SYNC to ground increases the switching frequency (up to 1MHz). Connecting the gate signal from another PWM IC synchronizes the ISL6534 switchers to the frequency of the other controller. This allows independent regulators operating at a common frequency to avoid low-frequency beats. The gate drivers for DDR mode can be staggered by 90° in order to minimize cross-conduction. Switcher OUT1 has an inter...