High-side MOSFET driver ....

Thread Starter

daba1955

Joined Apr 27, 2019
130
I have just remembered I did this on a project a couple of years ago, but on that project VD was +6V (VCC still at 5V). I did not have any issues and everything worked OK.
 

Thread Starter

daba1955

Joined Apr 27, 2019
130
OMG ! How confusing is that ! I thought the IRFZ34N and the IRF9Z34N were the same animals, in slightly different skins, but a quick google reveals all.

Anyway I will be using the IRF9Z34Ns in this new project.
 

Kjeldgaard

Joined Apr 7, 2016
451
Maybe one of the Open Drain Output shift register types, like the TPIC6C595?

However, the TPIC6x595 is neither pin- nor function compatible with the 74HC595!
 

Sensacell

Joined Jun 19, 2012
2,821
But doesn't the worst-case VOL of the 595 at 0.33V turn the FET off ?
It's a PFET with the source connected to 12V, setting the output low makes Vgs = 12 V - even more ON than before!
Add an NPN transistor with the collector connected to the gate - then the Vgs can swing between 0 - 12V and all is good.
 

Thread Starter

daba1955

Joined Apr 27, 2019
130
It's a PFET with the source connected to 12V, setting the output low makes Vgs = 12 V - even more ON than before!
So basically I just "got away with it" on the older project with VD at 6V ?

I would have to redesign PCB layout to switch VD to the VCC supply, or change the DC input voltage to a 6V supply, which I know works (at least it has on at least two builds of the old project).

Or have I just been lucky with Vgs = 1V turning the FETs off ?
 
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