ZeST and HSO phase voltage filtering and ADC requirements?

[StefanH]

I'm finalizing the design of a BLDC motor controller (up to 48V / 40A) and I'd like it to work well with HSO and (when available) ZeST.

From other forum posts I've found the need for phase voltage measuring and to be able to capture these simultaneously. The board already on the face of it the current board config looks compatible:

• STM32G473 MCU
• In-phase shunts (and an external 50x bi-directional OPAMP)
• ADC (rank) assignment:
  • ADC1: VM / bus voltage; 2 extra (low speed) voltage inputs and several NTCs
  • ADC2: Phase A voltage & Current
  • ADC3: Phase B voltage & Current
  • ADC4: Phase C voltage & Current
• Filtering (low-pass cut-off frequencies):
  • VM/bus voltage: 1.5kHz (fixed)
  • Phase current & phase voltage: 12 or 150 kHz (all voltage filters switch together, all current filters switch together)

Questions:

1. Is the above ADC configuration compatible with ZeST and HSO? If not, what should be changed?
2. What is the optimal low-pass cut-off frequency for the phase currents for HSO and ZeST?
3. Likewise for the phase voltage filters?

[DBE · Accepted solution]

Hello,

Please find below the answers to your question:

1. This ADC configuration should be compatible with HSO/ZeST

Regarding the filtering, you can refer to https://www.st.com/en/evaluation-tools/steval-lvlp01.html and https://www.st.com/en/evaluation-tools/b-g473e-zest1s.html which is a pack designed to use HSO/ZeST.
2. In the pack there is a 328KHz cut-off frequency for phase current.
3. 500Hz cut-off frequency is OK for phase voltage sensing. In the pack, it is 518Hz.

Best regards

[StefanH]

Thank you for the clear answers!

[MichaelM_Oscilla]

Hi StefanH!

In your post you mentioned: "From other forum posts I've found the need for phase voltage measuring and to be able to capture these simultaneously."

What post did you find that in? Is there a general design guide to creating custom power stages? Any pointers would be appreciated 🙂