9.2.2.2 Detailed Design Procedure

The basic components used in Figure 32 are reused here in Figure 38. The additional circuitry needed for source control will be discussed. Adding a blocking FET while using the bq51003 for control is the only addition to the circuitry. The AD pin will be tied to the DC input as a threshold detector. The AD_EN pin will be used to enable or disable the blocking FET. The blocking FET must be chosen to handle the appropriate current level and the DC voltage level supplied from the input. In this example, the expectation is that the DC input will be 5 V with a maximum current of 500 mA (same configuration as the wireless power supply). The CSD75207W15 is a good fit because it is a P-Channel, –20-V, 3.9-A FET pair in a 1.5-mm² WCSP.