Fujitsu MB3878 manual AC Adaptor Voltage Detection, Operation Timing Diagram

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MB3878

■AC ADAPTOR VOLTAGE DETECTION

With an external resistor connected to the +INE2 terminal(pin 3), the IC enters the dynamically-controlled charging mode to reduce the charge current to keep AC adaptor power constant when the partial potential point A of the AC adaptor voltage (Vcc) becomes lower than the voltage at the -INE2 terminal.

AC adaptor detected voltage setting: Vth Vth (V) = (R1 + R2) / R2 ⋅ −INE2

−INE2 setting voltage range : 1.176 V to 4.2 V (equivalent to 7 V to 25 V for Vcc)

<Error Amp.2>

	−INE2
	4	−
VCC	A	+
VCC	3	+
R1	+INE2
R2

■ OPERATION TIMING DIAGRAM
			2.5 V
Error Amp.1 FB1
Error Amp.3 FB3
Error Amp.2 FB2			1.5 V
			1.5 V
OUT
AC adaptor dynamically-	Constant	Constant current control	AC adaptor dynamically-
controlled charging	voltage control		controlled charging

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Contents Features DescriptionPackage TOP View PIN AssignmentPIN Description Pin No Symbol DescriptionsBlock Diagram Parameter Parameter Symbol Conditions Rating Unit Min MaxAbsolute Maximum Ragings Recommended Operating ConditionsParameter Symbol Pin Conditions Value Unit Min Typ Electrical CharacteristicsOutd = 1 mA 100 On resistor Parameter Symbol Pin Conditions Value Unit Min Typ Max200 Amplifier block Output source Typical Characteristics Triangular wave oscillator Deg Functional Description Bias voltage block VH PWM comparator block PWM CompOutput block OUT Control block CTLMethod of Setting the Triangular Wave Oscillator Frequency Setting the Charging VoltageMethod of Setting the Charging Current Method of Setting the SOFT-START TimeAC Adaptor Voltage Detection Operation Timing DiagramVcco OUT VIN Batt Processing Without USE of the CS PINOUTC2 Application ExampleParts No Batt Reference DataVCC Vishay Siliconix MB3878PFV Usage PrecautionsOrdering Information Part number Package RemarksIndex Package DimensionFujitsu Limited