8.3.6.2 Dynamic Power Management

To meet the maximum current limit in the USB spec and avoid over loading the adapter, the device features Dynamic Power Management (DPM), which continuously monitors the input current and input voltage. As the charger's system load plus charge current increases with constant input voltage, the charger's input current must increase. If this current exceeds the charger's preset input current limit or causes the input source voltage to droop near the input voltage limit (VINDPM fixed at 4.3 V typical), the device then reduces the charge current until the input current is regulated to the input current limit or the input voltage is regulated to the VINDPM threshold.Note that if the D+/D- algorithm detected a DCP port and VINDPM triggered, the ICO algorithm lowers the input current limit.

If the charge current is reduced to zero, but the input source is still overloaded, the system voltage starts to drop. Once the system voltage falls below the battery voltage, the device automatically enters the Supplement Mode where the BATFET turns on and battery starts discharging so that the system is supported from both the input source and battery.

The figure shows the DPM response with 5-V/3-A adapter, 6.4-V battery, 1.5-A charge current and 6.8 V minimum system voltage setting.

Figure 15. DPM Response