Fujitsu MB3887 manual AC Adaptor Voltage Detection, Operation Timing Diagram

MB3887

■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 adapter power constant when the partial potential point A of the AC adapter voltage (VCC) becomes lower than the voltage at the −INE2 terminal.

AC adapter detection voltage setting : Vth

Vth (V) = (R1 + R2) / R2 ⋅ −INE2

<Error Amp2>

	−INE2
	4	−
VCC	A	+
	3
R1	+INE2
R2

■OPERATION TIMING DIAGRAM

Error Amp2 FB2

Error Amp1 FB1

2.5 V

Error Amp2 FB3

1.5 V

OUT

Constant voltage control	Constant current control	AC adapter dynamically-
		controlled charging

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