Hi everyone,
I am designing DC/DC converter for high frequency applications. I am using current close loop control to control the converter. Now, the Xc164Cs has in built ADC. I need to check the output voltage and the current as well as input voltage and the current of the converter. I just want to know "how quickly i need to measure the inputs?" and how can i check that?
Cheers
vivek
Are you going to let the processor be in the control loop, or just supervise?
You normally don't include the processor in the control loop of a DC/DC.
Hi
Yes, you are right. I just want to check it. I am not going to do the processor into close loop. just supervise it. I just want to check that how quickly I measure my signals? and how quickly I sampled each input?
Vivek
The information you are seeking can be found in the data sheet and users manual.
For an analog to digital conversion the fastest you can perform a conversion is from the following formulas:
conversion time (10-bit) = 40 * tBC + tS + 6 * tSYS conversion time (8-bit) = 32 * tBC + tS + 6 * tSYS
Conditions... 1) The maximum frequency of the ADC Base Clock is 20MHz. 2) The maximum SYStem clock is 40MHz 3) The minimum Simple Time = tBC * 4 * (<ADSTC> + 1) 4) Post calibration is off
Assumptions: fSYS = 40 MHz (i.e. tSYS = 25 ns), ADCTC = '01', ADSTC = '00' Basic clock fBC = fSYS / 2 = 20 MHz, i.e. tBC = 50 ns Sample time tS = tBC * 8 = 400 ns
Conversion 10-bit: With post-calibr. = 52*tBC + tS + 6*tSYS = (2600 + 400 + 150) ns = 3.15 us Post-calibr. off = 40*tBC + tS + 6*tSYS = (2000 + 400 + 150) ns = 2.55 us
Conversion 8-bit: With post-calibr. = 44*tBC + tS + 6*tSYS = (2200 + 400 + 150) ns = 2.75 us Post-calibr. off = 32*tBC + tS + 6*tSYS = (1600 + 400 + 150) ns = 2.15 us
Nyquist criterion my friend: sample rate = 2*frequency of signal to be sampled. Application: Universal