TMS320F28377S: Buffered DAC clock

Kishen Someshwar

Part Number: TMS320F28377S
Other Parts Discussed in Thread: CONTROLSUITE

Hello Team,

I have a customer who is trying to find out the max clock for the buffered DAC for the F28377S device. After going through the clock structure and the DAC block diagram the customer has come with the following feedback :

" I painstakingly studied the clocking system. Here is the scheme related to buffered DAC. In this scheme XL(reference osc)-> PLL (multiplier)-> PCLKCR13(gate for DACa). According to it the DAC clock is set to SYSCLK of 200 MHz. Am I correct? I do not mess with system PLL which sets up CPU clock that is done by SysCtrl.c file. I am asking a simple question What is the buffered DAC clock, that I as well draw in the attached picture. "

How is the buffered DAC gated.

Thank you for your time,

Kishen

over 8 years ago

0 Frank Ankapong over 8 years ago

TI__Mastermind 28275 points

Hi Kishen,

The buffered DAC is clocked off SYSCLK. There isn't a local clock divider to the buffered DAC. So if your CPU is running at 200MHz, the buffered DAC is being clocked at 200MHz. The clock to the buffered DAC is only used for writes to the buffered DAC registers.

0 Kishen Someshwar over 8 years ago in reply to Frank Ankapong

TI__Intellectual 1625 points

Thank you Frank.

0 Frank Ankapong over 8 years ago in reply to Kishen Someshwar

TI__Mastermind 28275 points

Glad I could help. Let us know if you have any more questions.

0 Kishen Someshwar over 8 years ago in reply to Frank Ankapong

TI__Intellectual 1625 points

Hello Frank,

So if the customer wanted to adjust the sampling frequency, he should look at SYSCLK ?

Kishen

0 Frank Ankapong over 8 years ago in reply to Kishen Someshwar

TI__Mastermind 28275 points

Yes. So there are a few ways to update the DAC at a set frequency.
1. You can setup a timer interrupt and within that interrupt, you update the DAC. This will be the most CPU intensive. There are a few DAC examples in controlSUITE (buffdac_sine, buffdac_ramp) that do this.
2. You can setup the DMA to update the DAC.
3. You can configure the DAC to load from it's shadow register on a PWMSYNC signal.

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TMS320F28377S: Buffered DAC clock