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Helpful ReplyHot!ADC Conversion Time Calculation in 12 bit operation dsPIC33EP512GM710

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joshua.cochran
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2018/11/01 13:51:01 (permalink)
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ADC Conversion Time Calculation in 12 bit operation dsPIC33EP512GM710

Hello all,
 
I am new to Microchip devices and I am using a dsPIC33EP512GM710 on a Explorer 16/32 development board to sample using an ADC at 12 bit resolution.
 
I would like to sample at 400 kHz, just shy of the maximum 500 kHz speed advertised by the board. I am using the internal clock for timing the ADC, and the internal counter ends sampling and starts conversion (SSRC = 7). 
 
My question:
The manual for the ADC for this microcontroller family states that "The ADC conversion time will be 12 TAD since the ADC module is configured for 10-bit operation, as calculated in Equation 16-9"
 
Is this true for 12 bit operation as well? Or is it 14 TAD?
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du00000001
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Re: ADC Conversion Time Calculation in 12 bit operation dsPIC33EP512GM710 2018/11/01 14:01:57 (permalink)
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I didn't check the data sheet (expect to find an equation for 12 bit conversions as well), but expect that 12 bit conversions take (at least) 2 TAD more than 10 bit conversions.
So 14 seems to be reasonable.

PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
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jtemples
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Re: ADC Conversion Time Calculation in 12 bit operation dsPIC33EP512GM710 2018/11/01 14:04:07 (permalink) ☄ Helpfulby joshua.cochran 2018/11/01 17:20:18
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Look at Table 33-59.
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joshua.cochran
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Re: ADC Conversion Time Calculation in 12 bit operation dsPIC33EP512GM710 2018/11/01 17:24:24 (permalink)
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Wow, thank you. I would have never found that table. I think I can work this out tomorrow using that table!
 
Also, do you know what the MCC (or compiler) defaults to if I have the ADC setup to run faster than possible?
 
For instance, the MCC only throws a warning telling me that TAD < minimum TAD of 11.76e-8s -- it still compiles and APPEARS to sample correctly even though I had TCY = 1, TAD = 1 with conversion clock source as FOSC/2.
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