MP2611 – 2A, 1-CELL SWITCHING CHARGER FOR USB AND ADAPTER POWER

MP2611 Rev. 1.12

www.MonolithicPower.com

19

12/7/2012

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TYPICAL APPLICATION CIRCUITS

Power-Path Management

Power-path applications require powering the

system while simultaneously charging the battery.

Traditional designs adopt the simplest battery-fed

topology that connects the system to the battery

directly. An obvious drawback is that it cannot

operate the system with a drained battery.

Figure 7 shows an improved battery-fed topology.

The additional circuit between the current sense

resistor and the battery works like a variable

resistor. While the battery voltage is less than the

then in series with the battery to raise the system

the system can also operate at low battery

voltage. While the battery voltage is high enough,

reduce power loss.

Figure 7: Improved Battery-Fed Power-Path Management Structure

The power-path auto-selection topology shown in

Figure 8 adopts external switches to decouple

the system supply and battery charging process.

Thus the adapter directly powers the system

independent of the battery’s state as long as the

adapter is plugged in. If the adapter is absent,

the battery supplements the system.

Replace M1 and M2 with a power diode each, to

reduce the costs. However, the efficiency may

decline due to the forward voltage drop of the

diode. Even USBIN is not used, a least 4.7μF

capacitor is necessary connecting the pin to GND.

Figure 8: Power-Path Auto-Selection Structure