Fujitsu MB3878 manual AC Adaptor Voltage Detection, Operation Timing Diagram

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	+
	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
OUT
AC adaptor dynamically-	Constant	Constant current control	AC adaptor dynamically-
controlled charging	voltage control		controlled charging

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