AMC1311: Phase Voltage Sensing for 12 bit ADC

Dear Phan, 

Thank you for your interested in TIDA-00366 and C2000 InstaSPIN-FOC and MOTORWARE. Please see below regarding your questions.

1. Does that mean I need to use 1.65VREFGND for bidirectional voltage for AC voltage sensing?

[Martin] This is needed for bipolar signals. However when we measure the phase voltage versus DC- (PGND) we don't need, as this will be a unipolar voltage starting from 0 up to the DC-bus voltage, e.g. 72VDC.

2. How can I choose above Variables in MOTORWARE?

[Martin] You may refer to hvkit_rev1p1 example in MOTORWARE: TI\MOTORWARE\motorware_1_01_00_18\sw\solutions\instaspin_foc\boards\hvkit_rev1p1\f28x\f2806xF\src

The below is the corresponding entries in the user.h file for the hvkit_rev1p1: 
 
//! \brief Defines the maximum current at the AD converter
//! \brief The value that will be represented by the maximum ADC input (3.3V) and conversion (0FFFh)
//! \brief Hardware dependent, this should be based on the current sensing and scaling to the ADC input
#define USER_ADC_FULL_SCALE_CURRENT_A        (19.89)     // 19.89 hvkit_rev1p1 current scaling

//! \brief Defines the maximum voltage at the input to the AD converter
//! \brief The value that will be represented by the maximum ADC input (3.3V) and conversion (0FFFh)
//! \brief Hardware dependent, this should be based on the voltage sensing and scaling to the ADC input
#define USER_ADC_FULL_SCALE_VOLTAGE_V       (409.6)      // 409.6 hvkit_rev1p1 voltage scaling 

//! \brief ADC voltage offsets for A, B, and C phases
//! \brief One-time hardware dependent, though the calibration can be done at run-time as well
//! \brief After initial board calibration these values should be updated for your specific hardware so they are available after compile in the binary to be loaded to the controller

#define   V_A_offset    (0.2433366776)
#define   V_B_offset    (0.2432493567)
#define   V_C_offset    (0.2434823513)

I’d recommend you compare your hardware configuration versus the hvkit_rev1p1 and update the scaling accordingly. 

For more question on InstaSPIN-FOC and MOTORWARE, I’d recommend you post in the C2000 MCU E2E forum to reach our C2000 experts: https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum

Regards,
Martin Staebler