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Do I understanding the ADC behavior wrong? ACQT too big

 
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E_Blue



Joined: 13 Apr 2011
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Do I understanding the ADC behavior wrong? ACQT too big
PostPosted: Thu Nov 26, 2015 8:38 am     Reply with quote

In the table 21-1 of datasheet 39775c (PIC18F87J50) at page 307 recommends a TAD of Fosc/64 and TACQ of TAD*16 for 48MHz operation.

So if I'm correct that means a TACQ of 21.333µS

TosC = 1/48MHz= 0.02083µS
TAD = TosC * 64= 1.333µS
TACQ = TAD * 16 = 21.333µS

But according to the equation 21-3 at page 306 of the same datasheet the minimum TACQ is 2.45µS, so, as far I can understand that means that I can set a TACQ multiplier of 2*TAD.

Is my reasoning correct?

If the TACQ is too big I get less conversions per time unit but there's no other negative consequences, Right?
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Ttelmah



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PostPosted: Thu Nov 26, 2015 9:37 am     Reply with quote

I don't see anywhere where it suggests TAD*16 for Tacq?.
E_Blue



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PostPosted: Thu Nov 26, 2015 11:09 am     Reply with quote

You are right, my mistake I saw the ADCs2:0 column as ACQT2:0
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Ttelmah



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PostPosted: Thu Nov 26, 2015 3:29 pm     Reply with quote

I had a faint suspicion when I looked at the table.

Anyway, at least you have your answer!. Smile
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