what is exact Tacq necessory and how to use PIC18F2550

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ep.hobbyiest

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I am using pic18f2550 pic. and configuring ADC. but in that i am not geting exactly acquasition time require for ADC. Is time we have to wait for ADC conversion or start up time.?
Is that delay for conversion?
i m using pic at 20MHz crystal.

- - - Updated - - -

TACQ = Amplifier Settling Time + Holding Capacitor Charging Time + Temperature Coefficient
= TAMP + TC + TCOFF
Click to expand...

In this formula what is to take TAMP?
is it fixed of 0.2 us or depends on Machine cycle time.?
and other parameters are fixed i think.
 

hi,
The d/s for the 18F2550 shows the Tamp [ Amp settling time as typically 0.2uS.]

Use the values and formula shown in Fig #21-3.

This gives the time period you must wait before reading the ADC registers.

E
 

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Thanks but i saw that page.
This what formula i have written but i didn't get the concept plz explain.
 

hi ep.
I see that some of the values used in the d/s formula example are incorrect.?:?:

I will check further and let you know what I find.

Eric
 

hi ep,
Checking the maths and stated values in the 18F2550 datasheet for the AD acquisition times shows that the example is wrong.
Perhaps other members could double check my conclusions.? [shown in the attached image]

I have compared a number of d/s for the 16F and 18F and it appears that 'older' parts of the 16F series d/s ADC data has been copied into the 18F series d/s.

Look thru this adc.pdf for guidance on how to calculate the Tacq and the conversion times for the ADC.
Page #18 shows the use of the ADCONO.GO flag usage to check that the conversion is complete.

E
 

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