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| UB2016 Datasheet, PDF (11/13 Pages) Unisonic Technologies – ONE-CELL STANDALONE LINEAR LITHIUM BATTERY CHARGER | |||
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UB2016
Preliminary
 APPLICATION INFORMATION(Cont.)
CMOS IC
Reverse Polarity Input Voltage Protection
In some applications, protection from reverse polarity voltage on VCC is desired. If the supply voltage is high
enough, a series blocking diode can be used. In other cases, where the voltage drop must be kept low a P-channel
MOSFET can be used.
Fig. 4 Low Loss Input Reverse Polarity Protection
USB and Wall Adapter Power
The UTC UB2016 allows charging from both a wall adapter and a USB port. Fig. 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 1k⦠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 10k⦠program resistor are used to increase the charge
current to 600mA when the wall adapter is present.
Fig. 5 Combining Wall Adapter and USB Power
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
11 of 13
QW-R502-869.a
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