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Cell phone battery charger

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neoflash

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Guys,

When the cell phone is in charger mode, the internal circuits are still supplied with the battery or some LDO from the charger line?

For example, the PMU will disconnect the battery and connect another LDO to supply the internal circuits?

Also, another question is that when the battery is in charging mode, what is the voltage waveform appears at its nodes?

Thanks,
Neo
 

The internal circuit (LDOs and bucks) are supplied from the battery, always. It is never disconnected in a real application.
 
Then, what is going to happen when the battery is in charging mode by a smart charger?
 

ejeet said:
The internal circuit (LDOs and bucks) are supplied from the battery, always. It is never disconnected in a real application.
Click to expand...

This is the simple low cost way but not always. Many Motorola phones have switchover capability between battery and charger sourcing. They can run with dead battery or even no battery installed at all.
 

neoflash said:
Then, what is going to happen when the battery is in charging mode by a smart charger?
Click to expand...

Why is this a problem, do you mean? The internal circuits are not supplied directly from VBAT. There is always an LDO or a Buck between that regulates the voltage. Of course these are also internal circuits in the analog ASIC, but they can withstand a varying voltage input.
 

I would like to build a Impulse cell phone battery charger with USB output. It will be some kind universal charger. Input Voltage 230V - Output Voltage 5V. Is there any body who have design of this? I'm will be very glad ;)
 

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