ME4057

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time, if

ME4057 stay in under-voltage state, when VCC becomes too low in voltage mode. Fig.4 shows how the

voltage reduced with increase RCC value in this circuit. This technique will act the best function when in order to

maintain the minimize the dimension of the components and avoid voltage decreased to minimize RCC .

VCC bypass capacitor

Many types of capacitors can be used for input bypassing, however, caution must be exercised when using

multilayer ceramic capacitors. Because of the self-resonant and high Q characteristics of some types of ceramic

capacitors, high voltage transients can be generated under some start-up conditions, such as connecting the charger

input to a live power source. Adding a

1.5Ω resistor in series with a ceramic capacitor will minimize start-up voltage

transients.

Charging Current Soft Start

ME4057 includes a soft start circuit which used to maximize to reduce the surge current in the begging of charge

cycle. When restart a new charge cycle, the charging current ramps up from 0 to the full charging current within

20μs.

In the start process it can maximize to reduce the action which caused by surge current load.

USB and Wall Adapter Power

ME4057 allows charging from a USB port, a wall adapter can also be used to charge Li-Ion/Li-polymer batteries.

Figure 5 shows an example of how to combine wall adapter and USB power inputs. A P-channel MOSFET, M1, is

used to prevent back conducting into the USB port when a wall adapter is present and Schottky diode, D1, is used to

prevent USB power loss through the 1K

Ω pull-down resistor.

Generally, AC adaptor is able to provide bigger much current than the value of specific current limiting which is

500mA for USB port. So can rise charge current to 600mA with using a N-MOSFET (MN1) and an additional set

resistor value as high as 10K

Ω.

Fig.3:A circuit to maximum the thermal

regulation charge current

Fig.4:The relationship curve between charge

current with RCC

ME4057