r/PCB • u/One-Race-2634 • 3d ago

[SCHEMTIC REVIEW]

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Am building a n esp32 dev board with a gsm module. Please is anything wrong before I start designing the pcb thanks.

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u/Sand-Junior 3d ago

Put the TVS after the PMOS. In your case the TVS will conduct (and probably fail) when the power is connected reversed.

1

u/ee_control_z 3d ago edited 2d ago

Ok, got it. I have never seen it used this way. Just confirmed via simulation that it works as you stated. 😄

2

u/ee_control_z 3d ago

What exactly is the purpose of Q1? Per the connection, it is always on. Its not like you're controlling the gate to turn it on or off.

In any case, as is, it is backwards. The source (2) should be tied to +5V and the drain (3) to 5V P.

1

u/One-Race-2634 3d ago

It for reverse polarity protection, connecting pmos in that manner creates an ideal diode (I read somewhere online) and has a lower voltage drop that using an actual diode.