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Hardware support => General topics => Topic started by: gregcope on December 02, 2018, 12:06:53 PM

Title: Goto P-fets+fuses for input protection (12-24V)
Post by: gregcope on December 02, 2018, 12:06:53 PM
Hi,

Does anyone have any goto parts for VCC input protection?  I am thinking poly fuses and P-fets.  Through holes best!  Also I need to protect from VCC being over 36V (regulator accepts upto 55V) for a 24V nominal circuit.  I only need 0.25A at 12V (600ma at 5v).
Title: Re: Goto P-fets+fuses for input protection (12-24V)
Post by: Felix on December 03, 2018, 04:03:46 PM
What types of protection?
Just over voltage?
Title: Re: Goto P-fets+fuses for input protection (12-24V)
Post by: gregcope on December 20, 2018, 06:54:02 AM
Over current/voltage?
Reverse polarity?
Title: Re: Goto P-fets+fuses for input protection (12-24V)
Post by: Felix on December 20, 2018, 02:28:56 PM
You can use a PFET for reverse polarity - drain to your battery, source to your load, gate to GND, easiest thing ever, almost no leakage, no voltage drop:
(https://i.imgur.com/qMtjCIF.png)

I would also read this excellent resource from Maxim on reverse protection: https://www.maximintegrated.com/en/app-notes/index.mvp/id/636

You can use a MOV for transient input protection, typically in higher voltage applications.
If you want close to 0 leakage, you can use a set of generic BJTs (ex 2N3904), as explained here (https://www.eevblog.com/forum/beginners/multimeter-input-protection-what-are-these-bjts-doing/).

For overcurrent, use a fuse, PTC etc.

I will also add this video with some extras and demo:
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