SPRUHJ1I January 2013 – October 2021 TMS320F2802-Q1 , TMS320F28026-Q1 , TMS320F28026F , TMS320F28027-Q1 , TMS320F28027F , TMS320F28027F-Q1 , TMS320F28052-Q1 , TMS320F28052F , TMS320F28052F-Q1 , TMS320F28052M , TMS320F28052M-Q1 , TMS320F28054-Q1 , TMS320F28054F , TMS320F28054F-Q1 , TMS320F28054M , TMS320F28054M-Q1 , TMS320F2806-Q1 , TMS320F28062-Q1 , TMS320F28062F , TMS320F28062F-Q1 , TMS320F28068F , TMS320F28068M , TMS320F28069-Q1 , TMS320F28069F , TMS320F28069F-Q1 , TMS320F28069M , TMS320F28069M-Q1
The voltage filter pole is needed by the FAST estimator to allow an accurate detection of the voltage feedback. The filter should be low enough to filter out the PWM signals, and at the same time allow a high-speed voltage feedback signal to pass through the filter.
As a general guideline, a cutoff frequency of a few hundred Hz is enough to filter out a PWM frequency of 10 to 20 kHz. The hardware filter should only be changed when ultra-high-speed motors are run, which generate phase-voltage frequencies in the order of a few kHz.
In this example, consider the Anaheim PMSM motor with a maximum speed of 8000 RPM with 4 pole pairs (533 Hz), along with the BOOSTXL-DRV8305 EVM with PWM running at 45 kHz. Considering the BOOSTXL-DRV8305 EVM hardware seen in HALF-BRIDGES & BEMF SENSE section in the BOOSTXL-DRV8305EVM User’s Guide, also shown in Figure 6-9.
The filter pole setting can be calculated as follows:
The following code example shows how this is defined in user.h:
#define USER_VOLTAGE_FILTER_POLE_Hz (344.62)