SC471

Synchronous Buck Controller with Multi-Level VOUT Transition Support POWER POWERMANAGEMENT MANAGEMENT Description The SC471/A is a versatile, constant on-time synchronous buck, pseudo-fixed-frequency, PWM controller intended for notebook computers and other battery operated portable devices. The SC471/A contains all the features needed to provide cost-effective control of system elements needing voltage slewing. Two integrated switches provide four resistor-programmable DC output voltages, controlled by the G0 and G1 inputs. The output voltage is adjustable from 0.75V to 5V. Additional features for each output include cycle-by-cycle current limit, voltage soft-start, under-voltage protection, programmable over-current protection, soft shutdown, automatic power save and non-overlapping gate drive. The SC471/A provides an enable input and a power good output which is automatically blanked during output voltage transitions. The constant on-time topology provides fast dynamic response. The excellent transient response means that SC471/A based solutions require less output capacitance than competing fixed-frequency converters. Switching frequency is constant until a step in load or line voltage occurs, at which time the pulse density and frequency will increase or decrease to counter the change in output voltage. After the transient event, the controller frequency returns to steady state operation. At light loads, the automatic power save mode reduces the SC471/A frequency for impro...