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Fairchild RC5042, RC5040 Device, Iload =13.9A, Description, Component Case Temperature, Comments

Models: RC5040 RC5042

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AN42				APPLICATION NOTE

Component Case Temperature

		Case Temperature	Case Temperature	Case Temperature
		(°C)	(°C)	(°C)
Device	Description	Iload= 9.9A	Iload= 12.4A	Iload =13.9A
Q3A	MOSFET	57	63	56.3
	K1388

Q3B	MOSFET	58	64	66.6
	K1388

L1	Inductor,	53	56	61.2
	Unknown

Q2	Schottky Diode	66	70	87
	2048CT

IC	Raytheon RC5040	52	54	58

Cin	Input Capacitor 1000∝F	38.2	36.8	39

Cout	Output Capacitor	35	34.8	38.2
	1500∝F

Note:

Case temperatures are all within guidelines. Our guideline is that case temperatures for all components should be below 105°C @25°C Ambient.

Comments:

Excellent input ripple voltage. Input ripple voltage is recommended to be less than 5% of the output voltage.

Evaluation Summary:

The on-board DC-DC converter is fully functional. It has excellent load regulation, transient response, and input voltage ripple.

Attachment A

Attachment B

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Fairchild RC5042 Device, Iload =13.9A, Description, Component Case Temperature, Comments, Evaluation Summary, Attachment A

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 ConfigurationDesign Equations Converter EfﬁciencyExample Implementing Short Circuit Protection Selecting the InductorShort 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 NOTEGuidelines for Debugging and Performance Evaluations TroubleshootingDebugging Your First Design Implementation Vout Performance EvaluationVout 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