Figure 5-4. External Power Input Resistors Dividers

R1 and R2 set a rough threshold for PFET Q1 enable, to detect whether the external adapter exists or not. It must be

set at a lower threshold than the PD70211 disable levels.

R3 and R4 set the PD70211 disable threshold.

Therefore, in case of 36V–57V external adapter, the disable setting can be selected as follows:

PFET enable threshold = 30V.

R1 and R2 setting must be such that the value of Q1 VGS is less than 20V at maximum voltage condition of the

external adapter.

R1 is selected as 2 kΩ.

R3 and R4 are set to the range of few kΩ (10’s of kΩ) using the following equation:

Using R3 = 15 kΩ, Vext_adapter = 33.7V, and from this data sheet PD70211_WA_EN = 2.4V as the turn OFF

minimum threshold.

Solving the equation, the valid resistor's values for an adapter of 36V and above are achieved.

For complete information and details of various connection methods, see www.microchip.com/DS00003472A.

PD70211

Applications Information

Datasheet

DS00003672A-page 29