SDU contactor FETs IC9 and IC11/contactors not pulling in

[johu]

As most of you know parts tend to go out of stock at JLCPCB and you have to do some last minute replacements to get your order through.

It so happened on the last batch of Tesla SDU boards. I had to find a new part for mosfets IC9 and IC11.

I chose CMB18N20 with a supposed maximum threshold voltage of 3V. So perfect for 3.3V operation.

Problem is: the real world threshold voltage seems to be much higher. The FET doesn't switch on, only if you lift the pin and supply it with a higher voltage it will switch.

If you don't use the SDU board for controlling your contactors you don't need to do anything. Maybe some parts actually come with the threshold voltage that is specified, in that case you don't need to do anything either.

But if you do you need to replace the FET with something that works. I think a smart low side switch such das VNB10N07TR-E is a fairly safe choice.

If you ordered the board from me and are having issues with the contactors please get in touch