Other Parts Discussed in Thread: C2000WARE
Hello there,
I have a topic regarding the synchronization feature of the Sigma-Delta module in the TMS320F28388D. I have serveral Delta-Sigma modulators connected to the controller (AMC1306, AMC1106 and AMC1305)
I implemented the following configuration for PWM1:
- ePWM is running at 100 MHz
- Up-counter with ValueTop = 2559. This leads to a carrier with period of 25,6us
- In Event Trigger Module SOCA is configured to trigger when CTR=ZERO
The capture compare unit eCAP3 is configured to produce a 10MHz clock signal. This signal is distributed to the different modulators and to the sigma delta clock inputs SD1_C1 and SD2_C1 of the TMS320F28388D.
The delta sigma units are configured like this:
- Modulator Mode 0 (Modulator clock rate equals the modulator data rate)
- Modulator clock for all sigma delta units is SD1_C1 resp. SD2_C1
- Data filters set to SINC2 filter
- Oversampling ratio is set to 128
- Data representation is 16-Bit
- The filters are configured to sync on a SOCA event of PWM1
The timing is in principle like this:
Data from the sigma delta modules is requested right after CTR = Zero event of PWM1. The behavior I see now is, that data is correct as long as the sync on SOCA is disabled. As soon as I enable synchronization only invalid data can be captured from the Sigma Delta modules (voltage values vary in range of 30V when input is 0V). My question is now, if the synchronization can be done in this way? Is it possible to resync the data filter in every second cycle? From my point of view the oversampling ratio counter is only synchronized one time right at the beginning. Afterward it should already be "in sync" when the SOCA event triggers to reset the counter. Or is synchronization more than just resetting the DOSR counter?
Hopefully I was able to describe this complex configuration with this short paragraph.
Regard,
Michael Kettler
