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Topic: Summary for power switching. (Read 2548 times) previous topic - next topic


Oct 09, 2010, 02:28 pm Last Edit: Oct 10, 2010, 05:15 am by apollo21 Reason: 1
Arduino uses an external power supply.
Turn off the computer while connected to USB.
In that case, there is an abnormally high current flows from power less frequently.
I, ICM7555 using a circuit designed.
I wanted to check the operation LTspice use.
However, NE555 found.
LTspice did not work.
I got the following display resistance to change.
ICM7555 is replaced by the following picture.


Oct 11, 2010, 04:51 am Last Edit: Oct 11, 2010, 03:38 pm by apollo21 Reason: 1
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.

The ICM7555
As input
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)



I knew 555 approximately several years before 20.
A priority of the input remembered a thing related to of a thing of next then when I investigated input and relations of the output.


I easily work if I determine that I apply this I more easily calculate a resistance level, and to become "THRSHOLD=CONTROL".

I finish it without I remove hysteresis movement, and considering a delicate part.

I changed the circuit of the Arduino power supply change suggestion.

The inside has a drive circuit of the high output,
I knew that I was usable in many aspects.

(I have bought "CMOS555" dozens of.)
I think about an applied circuit and use it.


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