9.2.7 ORing MOSFET Controller

The previous reverse current circuits may be combined to create an OR'ing supply controller, utilizing either the P-Channel or N-Channel topologies.

For the previous P-Channel circuit, if no negative input voltages are possible, and the input voltage is below the MOSFET's V_GS(MAX) , then D3, D4 and R4 may be eliminated (the D2 anode, U1 pins 2 and 5, and C1 can be directly grounded).

For the N-Channel circuit, the oscillator drive can be shared between the channels, or eliminated if a higher system voltage is available to provide the higher votlage.

Figure 72. N-Channel OR'ing MOSFET Controller