AVR-Chat

Ah, yes, I did miss that.  My scenario would have Vb >> Vcc applied to the
uC output pin when off.  I like the N-channel  fet approach to switch the
gate of the VP3203.   However, I do need to clarify one point.  In Graham's
post he says "To turn the whole thing on, we apply a high level to the drain
of the N-channel."   I assume he meant to the gate, not the drain?   Steve

 

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Tim Mitchell
Sent: Friday, December 14, 2007 8:41 AM
To: AVR-Chat@yahoogroups.com
Subject: RE: [AVR-Chat] Re: ADC Vref


Yes, the input protection diodes which Graham just pointed out to me
will pull down the gate of the fet to the micro's vcc which will cause
it to be turned on all the time.

You'll need to put in a n-channel fet or an npn pulldown, as Graham
originally suggested, to switch the gate of the p channel fet.

-- 
Tim Mitchell





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