# About EPWM BLOCK - TI C2000 DC/DC Buck Converter Example

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Burak Caykenari on 16 Sep 2020
Hello Everyone,
I have basic question about f28379d EPWM block in this example -> (https://www.mathworks.com/help/supportpkg/texasinstrumentsc2000/ug/dc-dc-buck-converter.html)
And I watched the related video about this example ---- > (https://www.youtube.com/watch?v=CstjgrGR7dY)
According to working principle of ADC , We don't make the ADC start of conversion,while pwm transitioning . For this reason ADC start of conversion launchs the conversion before the X(any time) of period.
In buck example with f28379d , and its EPWM block as following:
This is provided via CMPB value. Period is 1000. When counter is equai to CMPB value , ADC will start conversion as you can see at CMPB value.
But I didn't understand how to choose CMPB value as (15+54)/2 ? What are the mean 15 and 54 values ? Where do they come from ?
Can you explain briefly ?
Manythanks.
Burak .
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### Answers (1)

Venkatesh Chilapur on 16 Sep 2020
Hi,
The first factor i.e 15 is related to the ADC SOCx acquisition window. The second factor i.e 54 is time from the end of the S+H window until the ADC results latch in the ADCRESULTx register. Refer the ADC block in the model and the controller TRM for more details. Since we have 2 SOC's configured here, hence the mutiplication factor of 2.
HTH,
Regards,
Venkatesh C
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burak caykenari on 18 Sep 2020
Hi Venkatesh ,
Thank you for clear answers.
My final question, I'm asking for confirmation :)
'But lets say, you have one SOC in ADC-A module and other in ADC-C, since they are different ADC module, they can run parallel.'
In this time equation is (1000-(15+54)). ?
These informations which you gave was very useful , I really appreciate you .
Manythanks.
Venkatesh Chilapur on 18 Sep 2020
Correct!

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