FAN5240

The FAN5240 is a single output 2-Phase synchronous buck controller to power AMD's mobile CPU core. The FAN5240 includes a 5-bit digital-to-analog converter (DAC) that adjusts the core PWM output voltage from 0.925VDC to 2.0VDC, which may be changed during operation. Special measures are taken to allow the output to transition with controlled slew rate to comply with AMD's Power Now technology. The FAN5240 includes a precision reference, and a proprietary architecture with integrated compensation providing excellent static and dynamic core voltage regulation. The regulator includes special circuitry which balances the 2 phase currents for maximum efficiency.

At light loads, when the filter inductor current becomes discontinuous, the controller operates in a hysteretic mode, dramatically improving system efficiency. The hysteretic mode of operation can be inhibited by the FPWM control pin.

The FAN5240 monitors the output voltage and issues a PGOOD (Power-Good) when soft start is completed and the output is in regulation. A pin is provided to add delay to PGOOD with an external capacitor.

A built-in over-voltage protection (OVP) forces the lower MOSFET on to prevent the output from exceeding a set voltage. The PWM controller's overcurrent circuitry monitors the converter load by sensing the voltage drop across the lower MOSFET. The overcurrent threshold is set by an external resistor. If precision overcurrent protection is required, an optional external current-sense resistor may be used.