onsemi (Ansemi)

TSSOP-28

taping

2500

The FAN5026 PWM controller provides high efficiency and regulation for two adjustable output voltages in the 0.9v to 5.5V range required to power I/O, chipsets, and memory banks on high-performance computers, set-top boxes, and VGA cards. Synchronous rectification helps improve energy efficiency over a wide range of loads. Using MOSFET RDS(ON) as the current sensing component further improves energy efficiency. Feedforward ramp modulation, average current mode control scheme and internal feedback compensation provide fast response to load transients. Out-of-phase operation with 180° phase shift reduces input current ripple. By activating designated pins, the controller can be converted to a full DDR memory power scheme. In DDR mode, one of the channels tracks the output voltage of the other channel and provides output current sourcing and sinking—necessary to properly power the DDR chip. The buffered reference voltage required for this type of memory is also provided. The FAN5026 monitors these outputs and generates a separate PGx (power good) signal when soft start is complete and the output is within ±10% of its setpoint. Overvoltage protection prevents the output voltage from exceeding 120% of the set value. Automatically resumes normal operation when the overvoltage condition ceases. After the soft-start sequence for either output, the undervoltage protection latches the chip when that output falls below 75% of its programmed value. An adjustable overcurrent function monitors the output current by sensing the voltage drop across the low MOSFET. If accurate current sensing is required, an external current sense resistor can be used.