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Fairchild RC5042, RC5040 specifications AN42, Application Note

Models: RC5040 RC5042

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AN42	APPLICATION NOTE

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Fairchild RC5042, RC5040 specifications AN42, Application Note

Contents

Input Voltages Pentium Pro DC Power RequirementsIntroduction DC Voltage RegulationProcessor Voltage Identiﬁcation Output Ripple and NoiseEfﬁciency I/O ControlsRC5040 and RC5042 Description Output EnableDisable Simple Step-Down ConverterUpgrade Present UP# Power Good PWRGDOutput Enable OUTEN Main Control LoopShort Circuit Protection Design Considerations and Component SelectionOver-Voltage Protection OscillatorRC5042 Thermal MOSFET SelectionTwo MOSFETs in Parallel Conditions1Figure 6. Charge Pump Configuration MOSFET Gate BiasCharge Pump or Bootstrap Figure 7. 12V Gate Bias ConfigurationConverter Efﬁciency Design EquationsExample Selecting the Inductor Implementing Short Circuit ProtectionShort Circuit Comparator Description Discrete MetalDiscrete Resistor IRCMismatch due to L/W Resistor mΩSheet resistivity Thermal ConsiderationsOutput Current Figure 13. RC5040/RC5042 Short Circuit Characteristic RC5040 and RC5042 Short Circuit Current CharacteristicsPower Dissipation Consideration During a Short Circuit Condition OutputSchottky Diode Selection Input ﬁlter Table 10. Schottky Diode Selection TableOutput Filter Capacitors Bill of MaterialsVf0.72V @ If = 15A PCB Layout Guidelines and ConsiderationsPCB Layout Guidelines Optional - will help rePC Motherboard Layout and Gerber File = “Quiet” PinsAN42 APPLICATION NOTETroubleshooting Guidelines for Debugging and Performance EvaluationsDebugging Your First Design Implementation Performance Evaluation VoutVout Iload A Input Ripple and Power on Input Rush CurrentVout Output Voltage Load Transients Due to Load Current StepComponent Case Temperature DeviceIload =13.9A DescriptionAttachment C SummaryRC5040/RC5042 Evaluation Board Attachment EAppendix A Directory of Component Suppliers LIFE SUPPORT POLICY