UB6054A

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

11 of 13

www.unisonic.com.tw

QW-R502-926.b

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APPLICATION INFORMATION(Cont.)

Reverse Polarity Input Voltage Protection

enough, a series blocking diode can be used. In other cases, where the voltage drop must be kept low a Pchannel

MOSFET can be used.

Fig4. Low Loss Input Reverse Polarity Protection

USB and Wall Adapter Power

The UTC UB6054 allows charging from both a wall adapter and a USB port. Figure 5 shows an example of how to

combine wall adapter and USB power inputs. A P-channel MOSFET, MP1, is used to prevent back conducting into

the USB port when a wall adapter is present and a Schottky diode, D1, is used to prevent USB power loss through

the 1kΩ pull-down resistor. Typically a wall adapter can supply more current than the 500mA-limited USB port.

Therefore, an N-channel MOSFET, MN1, and an extra 10kΩ program resistor are used to increase the charge

current to 600mA when the wall adapter is present.

Fig5. Combining Wall Adapter and USB Power