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.

• CPU Core power: 0.925V to 2.0V output range
• ±1% reference precision over temperature
• Dynamic voltage setting with 5-bit DAC
• 6V to 24V input voltage range
• 2 phase interleaved switching
• Active droop to reduce output capacitor size
• Differential remote voltage sense
• High efficiency:
  • >90% efficiency over wide load range
  • >80% efficiency at light load
• Excellent dynamic response with Voltage Feed-Forward and Average Current Mode control
• Dynamic duty cycle clamp minimizes inductor current build up
• Lossless current sensing on low-side MOSFET or Precision current sensing using sense resistor
• Fault protections: Over-voltage, Over-current, and Thermal Shut-down
• Controls: Enable, Forced PWM, Power Good, Power Good Delay
• QSOP28, TSSOP28

• AMD Mobile Athlon™ CPU V_CORE Regulator
• Graphic chip V_CORE Regulator