The total input from an AC adapter or other DC source is a function of the system supply current and the battery charging current. System current normally fluctuates as portions of the systems are powered up or down. Without DPM, the source must be able to supply the maximum system current and the maximum charger input current simultaneously. By using DPM, the battery charger reduces the charging current when the input current exceeds the input current limit set by ACSET. The current capability of the AC adapter can be lowered, reducing system cost.
Similar to setting battery regulation current, adapter current is sensed by resistor RAC connected between ACP and ACN. Its maximum value is set by ACSET using Equation 3:
VACSET, the input voltage range of ACSET, is from 0 V to 2 V. The ACP and ACN pins are used to sense voltage across RAC with default value of 10 mΩ. However, resistors of other values can also be used. A larger the sense resistor gives a larger sense voltage and a higher regulation accuracy, but at the expense of higher conduction loss.