As a follow-up question to my previous question regarding a circuit that passes voltages above 17 V, I wanted to be sure how to connect output of the solution circuit to my application.

The output is +VIN_ALW and it feeds 3.3V DC/DC and 5V DC/DC, and it could pass max current of 3A, and it turns on when VIN_ALW_GATED > 17V based on TL431 circuit:

enter image description here Simulate this circuit - Schematic created using CircuitLab (Credit to the person who answered the previous question).

In case +VIN_ALW "0V (when VIN_ALW_GATED is not applied), I want to allow another rail to connect to +VIN_ALW, this rail is called VIN_ALW_NOT_GATED.

  1. do I need to connect D52 Diode? I'm not sure about it necessity but it originated in my mind from the fact that this connection looks like oring diodes, where the second diode is Q46 drain. (It's not accurate but I'm trying to explain my intuition).

  2. Is there a hard to connect VIN_ALW_NOT_GATED directly to Q46 drain when VIN_ALW_GATED is not applied? Note: VIN_ALW_GATED and VIN_ALW_NOT_GATED can't be connected at the same time

  3. Is my assumption right? that, when there is no power to VIN_ALW_GATED this this is like 0V? the rail in this case will be floating because it's fed from outside connector, so I'm not sure about the behavior of the circuit.



Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.