The FAN5026 PWM controller provides high efficiency and regulation for two output voltages adjustable in the range from 0.9v to 5.5V that are required to power I/O, chip-sets, and memory banks in high-performance computers, set top boxes, and VGA cards. Synchronous rectification contributes to high efficiency over a wide range of loads. Efficiency is even further enhanced by using MOSFET's R_DS(ON) as a current sense component.

Feed-forward 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. The controller can be transformed into a complete DDR memory power supply solution by activating a designated pin. In DDR mode of operation one of the channels tracks the output voltage of another channel and provides output current sink and source capability - features essential for proper powering of DDR chips. The buffered reference voltage required by this type of memory is also provided. The FAN5026 monitors these outputs and generates separate PGx (power good) signals when the soft-start is completed and the output is within ±10% of its set point. A built-in over-voltage protection prevents the output voltage from going above 120% of the set point. Normal operation is automatically restored when the over-voltage conditions go away. Under-voltage protection latches the chip off when either output drops below 75% of its set value after the soft-start sequence for this output is completed. An adjustable over-current function monitors the output current by sensing the voltage drop across the lower MOSFET. If precision current-sensing is required, an external current-sense resistor may optionally be used.

• Highly flexible dual synchronous switching PWM controller includes modes for:
  • DDR mode with in-phase operation for reduced channel interference
  • 90° phase shifted two-stage DDR Mode for reduced input ripple
  • Dual Independent regulators 180° phase shifted
• Complete DDR Memory power solution
  • VTT Tracks VDDQ/2
  • VDDQ/2 Buffered Reference Output
• Lossless current sensing on low-side MOSFET or Precision current sensing using sense resistor
• VCC Under-voltage Lockout
• Wide power input range: 3 to 16V
• Excellent dynamic response with Voltage Feed-Forward and Average Current Mode control
• Power-Good Signal
• Supports DDR-II and HSTL
• TSSOP28 package

• DDR V_DDQ and V_TT voltage generation
• Desktop computer
• Graphic cards