Fujitsu MB39A104 manual ESR ≤ ΠfC L 050 491

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MB39A104

• Smoothing Capacitor

The smoothing capacitor is an indispensable element for reducing ripple voltage in output. In selecting a smooth- ing capacitor it is essential to consider equivalent series resistance (ESR) and allowable ripple current. Higher ESR means higher ripple voltage, so that to reduce ripple voltage it is necessary to select a capacitor with low ESR. However, the use of a capacitor with low ESR can have substantial effects on loop phase characteristics, and therefore requires attention to system stability. Care should also be taken to use a capacity with sufficient margin for allowable ripple current. This application uses the (OS-CON TM) 6SVP82M made by Sanyo. The ESR, capacitance value, and ripple current can be calculated from the following formulas.

Equivalent Series Resistance : ESR

ESR ≤ ΔVO − 1

ΔIL 2πfCL

Capacitance value : CL

ΔIL

CL ≥ 2πf (ΔVO − ΔIL ⋅ ESR)

Ripple current : ICLrms (VIN − VO) ton

ICLrms ≥

2√3L

Example: Using the 6SVP82M

Rated voltage = 6.3 V, ESR = 50 mΩ, maximum allowable ripple current = 1570 mArms

Equivalent series resistance

CH1		ΔVO
ESR ≤		ΔVO		−		1
ESR ≤		ΔIL		−		2πfCL
≤	0.050			−		1
		0.491				2π ⋅ 500 ⋅ 103 ⋅ 82 ⋅ 10−6

≤98.0 mΩ

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Contents Features DescriptionPackage MB39A104 PIN AssignmentsPin No Symbol Descriptions PIN DescriptionBlock Diagram Absolute Maximum Ratings Parameter Symbol Condition Rating Unit Min MaxParameter Symbol Condition Value Unit Min Typ Recommended Operating ConditionsPin No Conditions Electrical CharacteristicsParameter Min Typ MaxParameter Symbol Pin No Conditions Value Unit MinTypical Characteristics Reference Voltage vs. Ambient TemperatureTriangular Wave Oscillation Frequency Power Dissipation vs. Ambient Temperature Functions Protection circuit operating function table Timer-latch overcurrent protection circuit block OCPUnder voltage lockout protection circuit Uvlo Operating circuitSetting the Output Voltage Setting the Triangular Oscillation FrequencySetting the SOFT-START and Discharge Times MB39A104 Treatment Without Using CS Terminal Without Setting Soft-Start TimeAbout TIMER-LATCH Protection Circuit Overcurrent detection circuitOvercurrent Protection Circuit Range of Operation Method to detect by mean currentTimer-latch short-circuit protection circuit Treatment Without Using Cscp Terminal Resetting the Latch of Each Protection CircuitEquivalent Circuit On Power on OFF Standby mode Parts List Component Specification VendorSelection of Components CH1CH2 = 3 2 ⋅ 0.05 ⋅ 0.174 = 0.078 W Example Peak-to-peak value ΔIL Di ≥ I O ⋅ 1 − ESR ≤ ΠfC L 050 491 ESR ≤ ΠfC L 033 364 Reference Data Total Efficiency vs. Input VoltageSwitching Wave Form CH1 Do not apply negative voltages Usage PrecautionOrdering Information Part number Package RemarksPackage Dimensions IndexFujitsu Limited