TMS320F28377D: What does SDFM module synchronization refer to in TMS320F28377D

Hui Chen

Hello there,

I would like to ask about the specific meaning of SDFM module synchronization in TMS320F28377D. My understanding is that the reset position of 4 counters in SDFM is determined by setting the CMPC or CMPD comparison value of PWM11, and the function of filter is re-executed from this position. Is this understanding correct?

Please let me know if you have any hint.

Thanks in advance.

Best regards

huichen

1 month ago

over 3 years ago

+1 Gus Martinez over 3 years ago

TI__Mastermind 30571 points

Hello,

Please check out the training videos on SDFM at the link below.

https://training.ti.com/sigma-delta-filter-module-sdfm-training-c2000-mcus

Specifically, the module below discusses the SDSYNC feature.

https://training.ti.com/sdfm-type0-overview?context=1150280-1149827

0 Hui Chen over 3 years ago in reply to Gus Martinez

Intellectual 890 points

Dear Gus Martinez ，

I am very glad to receive your answer. I still have some questions to ask. When the SDFM filter I configured is as follows, the filter type is sinc3, the data rate of the modulator is 20MHz, OSR=256, and the delay of the Sinc filter is 38.4us, the SDFM event synchronization method is used. When I get the first data after 38.4us occurs at the synchronization position, does the second data occur at the next 38.4us? Still like the principle of sampling window sliding, only wait 38.4us once and the next data will be calculated quickly.

Thanks in advance.

Best regards

huichen

+1 Gus Martinez over 3 years ago in reply to Hui Chen

TI__Mastermind 30571 points

Hui,

Hui Chen said:
When I get the first data after 38.4us occurs at the synchronization position, does the second data occur at the next 38.4us?

First thing to keep in mind is that the data rate is fixed. Per the TRM:

In your case, the data rate is 78.1kHz (12.8us). You will get data every 12.8us. Because you are using sync3, you have to discard the first 2 samples *after* the SDSYNC pulse. The SDSYNC feature only aligns the start of the conversion to the PWM pulse.

This post has a graph that maybe can help you understand this feature a little better:

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1162736/tms320f28388d-about-sdfm-settings/4373718?tisearch=e2e-sitesearch&keymatch=sdsync%25252520sdfm#4373718

0 Hui Chen over 3 years ago in reply to Gus Martinez

Intellectual 890 points

I am gratitude to you for helping me.

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TMS320F28377D: What does SDFM module synchronization refer to in TMS320F28377D