Therefore, roughly:

For a Boost or Buck-Boost, account for the fact must be made that the peak current is not just 1.3 times of maximum

load current, but it is actually:

Therefore, the following equation for sense resistor must be used.

For example, if the maximum load current is 5A, the sense resistor value to use is:

This is roughly half of the Buck (same load current).

For a Flyback topology (Buck-Boost with a transformer), the reflected output current is used:

5.8

Operation with an External DC Source

PD applications utilizing PD70211 IC might be operated with an external power source (DC wall adaptor). Figure 5-2

and Figure 5-3 show the two cases of providing power with an external source.

• External source connected to application’s low voltage supply rails. External source voltage level is dependent

on DC-DC output characteristics. See Figure 5-2 for more details.

• External source connected to PD device output connection towards the application (VPP to VPNOUT). External

source voltage level is dependent on DC-DC input requirements. See Figure 5-3 for more details.

PD70211

Applications Information

Datasheet

DS00003672A-page 27