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Current measurement in the example project Sensored FOC for DRV8301-LS12-KIT

Ros River
Prodigy 70 points

Other Parts Discussed in Thread: MOTORWARE, DRV8301

Dear Expert,

 I think there is an error/inconsistency  in the code of the TI's FOC software example for DRV8301-LS12-KIT (TMS570LS1227) Hercules_Motorware_Dec2012.zip.

My understanding (please correct me if something is wrong):  the ETPWM2A (=PWM_AH, First Half Bridge HB1) generates an event trigger at the end of each period (f=20kHz), this event triggers the AD-conversion, the only reference I find is adcStartConversion(adcREG1, adcGROUP1), so I look into s_adcSelect[0][1] and find the following channels: 9, 18, 21 >> According to the schematic (AD1IN9, AD1IN18, AD1IN21):

9=phase current in HalfBridge3 amplified via external TLV2781DBVR,

18 = VDCbus,

21=phase current in HalfBridge2 amplified internally in DRV8301,

Therefore two questions:

  1. Is it really so that two amplifiers are being combined - internal for one phase and external for the other? Why? 
  2. Why there is no discharge capacitor time between conversions, is it here in this application not necessary?

Thanks for your ideas!

Regards,

Ros