Mechanism of action described
In the early silicon diode circuit operation from the USB
4.3V power supply circuit through a voltage is applied near,
It does not flow in the opposite direction.
At the same time, PchMOSFET SW has the power of low voltage drop,
This device also has disadvantages flowing in the opposite direction by driving the gate.
Has a detection terminal voltage exceeds the control voltage terminal to terminal and launch detection voltage
Priority will be reset to the output> voltage terminal exceeding detection> detection voltage terminal sequence is started.
Voltage detection comparator has an internal reference voltage of the resistor network from windows
Suresshurudo input (detected voltage activated) and the trigger input (detection voltage excess) of hysteresis has.
As an output pin
And output terminals have a discharge output.
Output current discharge has the ability to breathe from the outside,
Since there is no ability to drive is not suitable for PchMOSFET spit.
The totem pole output circuit SEPP
Both have the ability to spit less output sink discharge.
Since a small current in CMOS circuit has a voltage swing on the lower end almost.
Added to the external resistor network terminal to terminal voltage exceeds the detection voltage detection start
Alleviate the effects of internal hysteresis voltage ratio given a fixed time.
Alters the voltage control voltage terminal through a resistor from the external voltage detection
Earlier than normal power supply cuts off the gate drive PchMOSFET.
External power supply - from the current from the constant voltage regulator through PchMOSFET
USB can not flow back to the circuit.
The external sense voltage does not exceed
Schottky diode clamp at the power terminals inside the terminal.
1nF capacitor to change,
100k plus one more point,
In addition to the load resistance 2k,
Before detection with an external voltage REG.
ICM7555 and the same circuit NE555
Now similar results.
The reference voltage Vcc of 5v to see.
(3.3v can be changed)