Facebook
Google
GitHub
Linkedin
Problem Description (Simple Explanation):
I am using an MT3608 boost converter (3.7–4.2V battery → 5V).
I want the boost to turn OFF completely when my BUCK +5.2V supply is present.
So I used a P-channel MOSFET to disable the EN pin.
This part works fine.
But I also don’t want any leakage/backfeed voltage at the boost output when the boost is OFF.
So I tried to route both the Boost VIN and EN pin through the MOSFET.
After doing this:
Main Issue:
I am using an MT3608 boost converter (3.7–4.2V battery → 5V).
I want the boost to turn OFF completely when my BUCK +5.2V supply is present.
So I used a P-channel MOSFET to disable the EN pin.
This part works fine.
But I also don’t want any leakage/backfeed voltage at the boost output when the boost is OFF.
So I tried to route both the Boost VIN and EN pin through the MOSFET.
After doing this:
Main Issue:
- The boost converter does not give output when load is connected.
- Even at 10 mA load, it doesn’t start.
- At 150 mA, also no output.
- But if I enable EN directly through MOSFET, and give buck input directly the boost works normally.
- So the problem is coming because VIN is also going through the MOSFET.
- I checked MOSFET separately → it does not pass enough current (10–150 mA) in this configuration.
- EN pin alone works because EN pin uses very small current.
- When MOSFET drives VIN, the boost cannot start because the MOSFET adds voltage drop or is not fully ON.
- No backfeed voltage on boost output when boost is OFF
- Boost should supply up to 150 mA when ON
- A simple solution using MOSFET or ideal diode
- MOSFET body diode is causing reverse current
- MOSFET is not fully turning ON (Vgs issue)
- Boost needs high startup current, but MOSFET is limiting it
- Maybe MOSFET needs back-to-back configuration to block reverse voltage
- Correct MOSFET configuration to block backfeed
- Should I use back-to-back MOSFETs or an ideal diode IC?
- Any simple fix so boost can start properly under load
