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MAX1551 Charger

MAX1551 / MAX1555 – specialized chargers for Li + batteries that can operate from USB or from a separate power adapter (for example, a charger from the phone).

The maximum input voltage from the DC adapter is 7 V, when powered from USB it is 6 V. When the supply voltage drops 3.52 V, the chip turns off and the charge process stops.

 

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The microchip itself detects at which input there is a supply voltage and connects to it. If the power goes through the USB bus, then the maximum charge current is limited to 100 mA – this allows the charger to be plugged into the USB port of any computer without fear of burning the south bridge.
When powered from a separate power supply, the typical charging current is 280 mA.
Overheating protection is integrated in the chips. But even in this case, the circuit continues to operate, reducing the charge current by 17 mA per degree above 110 ° C.
There is a pre-charge function (see above): as long as the voltage on the battery is below 3V, the microcircuit limits the charge current to 40 mA.
The chip has 5 pins. Here is a typical wiring diagram:

If there is a guarantee that the output of your adapter cannot under any circumstances exceed 7 volts, then you can do without the stabilizer 7805.

The USB charging option can be assembled, for example, on such a printed circuit board.

If there is a guarantee that the output of your adapter cannot under any circumstances exceed 7 volts, then you can do without the stabilizer 7805.

The USB charging option can be assembled, for example, on such a printed circuit board.