Maker : Fairchild Semiconductor
Part No. : RC5051

  Datasheet PDF : RC5051.pdf
  Cross Reference : RC5051 Cross Reference
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Product Information

www.fairchildsemi.com RC5051 Programmable Synchronous DC-DC Controller for Low Voltage Microprocessors Features • Programmable output from 1.3V to 3.5V using an integrated 5-bit DAC • 85% efficiency typical • Adjustable operation from 80KHz to 1MHz • Integrated Power Good and Enable functions • Overvoltage protection • Overcurrent protection • Drives N-channel MOSFETs • 20 pin SOIC package • Meets Intel Pentium II specifications using minimum number of external components Description The RC5051 is a synchronous mode DC-DC controller IC which provides an accurate, programmable output voltage for all Pentium II CPU applications. The RC5051 uses a 5-bit D/A converter to program the output voltage from 1.3V to 3.5V. The RC5051 uses a high level of integration to deliver load currents in excess of 19A from a 5V source with minimal external circuitry. Synchronous-mode operation offers optimum efficiency over the entire specified output voltage range, and the internal oscillator can be programmed from 80KHz to 1MHz for additional flexibility in choosing external components. An on-board precision low TC reference achieves tight tolerance voltage regulation without expensive external components. The RC5051 also offers integrated functions including Power Good, Output Enable, over-voltage protection and current limiting. Applications • Power supply for Pentium® II • VRM for Pentium II processor • Programmable step-down power supply Block Diagram +12V RC5051 1 – + +5V 5 4 OSC – + 13 12 – + – + DIGITAL CONTROL +5V 7 9 VO VREF 16 5-BIT DAC 20 19 18 17 8 1.24V REFERENCE POWER GOOD 2 3 PWRGD 65-5051-01 VID0 VID2 VID4 VID1 VID3 ENABLE Pentium is a registered trademark of Intel Corporation. REV. 1.0.4 4/2/01 RC5051 PRODUCT SPECIFICATION Pin Assignments CEXT ENABLE PWRGD IFB VFB VCCA VCCP VID4 LODRV GNDP 1 2 3 4 5 6 7 8 9 10 20 19 18 17 VID0 VID1 VID2 VID3 VREF GNDA GNDD VCCQP HIDRV GNDP RC5051 16 15 14 13 12 11 65-5051-02 Pin Definitions Pin Number Pin Name 1 CEXT Pin Function Description Oscillator Capacitor Connection. Connecting an external capacitor to this pin sets the internal oscillator frequency. Layout of this pin is critical to system performance. See Application Information for details. Output Enable. A logic LOW on this pin will disable the output. An internal pull-up resistor allows for either open collector or TTL compatibility. Power Good Flag. An open collector output that will be at logic LOW if the output voltage is not within ±12% of the nominal output voltage setpoint. High Side Current Feedback. Pins 4 and 5 are used as the inputs for the current feedback control loop. Layout of these traces is critical to system performance. See Application Information for details. Voltage Feedback. Pin 5 is used as the input for the voltage feedback control loop and as the low side current feedback input. See Application Information for details regarding correct layout. Analog VCC. Connect to system 5V supply and decouple with a 0.1µF ceramic capacitor. Power VCC for low side FET driver. Connect to system 5V supply and place a 1µF ceramic capacitor for decoupling and local charge storage. VID4 Input. A logic 1 on this open collector/TTL input will enable the VID3–VID0 inputs to set the output from 2.1V to 3.5V, and a logic 0 will set the output from 1.3V to 2.05V, as shown in Table 1. Pullup resistors are internal to the controller. Low Side FET Driver. Connect this pin to the gate of an N-channel MOSFET for synchronous operation. The trace from this pin to the MOSFET gate should be < 0.5". Power Ground. Return pin for high currents flowing in pins 7 and 13 (VCCP and VCCQP). Connect to a low impedance ground. High Side FET Driver. Connect this pin to the gate of an N-channel MOSFET. The trace from this pin to the MOSFET gate should be < 0.5". Power VCC. For high side FET driver. VCCQP must be connected to a voltage of at least VCCA + VGS,ON (MOSFET), and place a 1...

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