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C2000WARE: f28379d Recommended ADC Mapping for Accurate Sampling

Vijay Wankhede
Prodigy 120 points

Part Number: C2000WARE

Hi,

I would like to confirm whether the recommended ADC mapping is actually required to achieve accurate and reliable sampling.

I have attached screenshots showing:

The ADC mapping currently used in our design.
image.png
The recommended ADC mapping.

image.png

My main concern is understanding whether changing to the recommended mapping will provide a significant sampling benefit, or if the current configuration is already adequate.

The intention is to avoid unnecessary changes if the existing ADC allocation can still provide correct and consistent sampling performance.

Thank-you.

  • 0
    TI__Expert 6360 points

    Vinay,

    Presuming this inverter or PFC operation, In short I would say YES, your second choice is recommended for ADC mapping for following reason:

    1. All same entities (currents or voltage) of all the phases are sampled at the exact same time. This is recommended to avoid sampling offset in time which leads to calculation errors in algorithms like Park/Clarke transforms or 3-phase PLLs.

    2. Your current configuration is vulnerable to the cross talk since successive conversions on the same ADC module cause charge-sharing errors. Independent hardware channels convert in isolation for the same entity.

    3. Current config also increases the control loop latency since you have to wait for multiple sequential conversion cycles to finish on a single ADC before you can run the control code. In recommended config, all critical phase entities complete conversion concurrently. 

    Regards,

    Sumit