Fujitsu MB39A104 manual Setting the Output Voltage, Setting the Triangular Oscillation Frequency

Page 13

MB39A104

■SETTING THE OUTPUT VOLTAGE

•Output Voltage Setting Circuit

VO

R1

(−INE2) 15

10

−INE1

R2

(CS2)	14
CS1	11

	Error Amp
−			VO (V) =	1.24	(R1	+ R2)
+

				R2

+

1.24 V

■SETTING THE TRIANGULAR OSCILLATION FREQUENCY

The triangular oscillation frequency is determined by the timing capacitor (CT) connected to the CT terminal (pin 13), and the timing resistor (RT) connected to the RT terminal (pin 12).

Moreover, it shifts more greatly than the caluculated values according to the constant of timing resistor (RT) when the triangular wave oscillation frequency exceeds 1 MHz. Therefore, set it referring to “Triangular Wave Oscillation Frequency vs. Timing Resistor” and “Triangular Wave Oscillation Frequency vs. Timing Capacitor” in “ ■ TYPICAL CHARACTERISTICS”.

Triangular oscillation frequency : fOSC

1200000

fOSC (kHz) =: CT (pF) •RT (kΩ)

13

Image 13

Contents Description FeaturesPackage PIN Assignments MB39A104PIN Description Pin No Symbol DescriptionsBlock Diagram Parameter Symbol Condition Value Unit Min Typ Parameter Symbol Condition Rating Unit Min MaxAbsolute Maximum Ratings Recommended Operating ConditionsParameter Electrical CharacteristicsPin No Conditions Min Typ MaxPin No Conditions Value Unit Min Parameter SymbolReference Voltage vs. Ambient Temperature Typical CharacteristicsTriangular Wave Oscillation Frequency Power Dissipation vs. Ambient Temperature Functions Under voltage lockout protection circuit Uvlo Timer-latch overcurrent protection circuit block OCPProtection circuit operating function table Operating circuitSetting the Triangular Oscillation Frequency Setting the Output VoltageSetting the SOFT-START and Discharge Times MB39A104 Without Setting Soft-Start Time Treatment Without Using CS TerminalOvercurrent detection circuit About TIMER-LATCH Protection CircuitMethod to detect by mean current Overcurrent Protection Circuit Range of OperationTimer-latch short-circuit protection circuit Resetting the Latch of Each Protection Circuit Treatment Without Using Cscp TerminalEquivalent Circuit On Power on OFF Standby mode Component Specification Vendor Parts ListCH1 Selection of ComponentsCH2 = 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 Total Efficiency vs. Input Voltage Reference DataSwitching Wave Form CH1 Ordering Information Usage PrecautionDo not apply negative voltages Part number Package RemarksIndex Package DimensionsFujitsu Limited