SLAU958A January 2025 – March 2025 MSPM0G3507
Base current represents the maximum measurable motor phase current in the motor control system. The user inputs the system base current (in Amps) in the currentBase parameter of the System Configuration page in GUI. The user can compute the system base current based on the current sense amplifier gain (CSAGAIN) in volts/amp and the full-scale ADC voltage (FSV) of 3.3V and Zero Current Offset voltage from the CSA as shown in Equation 8:
In case of bidirectional current sensing the zero-current offset is often selected as 1.65V , half of ADC Full Scale Voltage 3.3V.
In case of Unidirectional Current Sensing, 80-90% of ADC Full Scale Voltage is typically used for +ve Current Sensing. In general, Unidirectional current sensing is used in single shunt DC Bus current sensing architecture.
If the system uses a current sense resistor (RSENSE) with CSAGAIN units mentioned in volts/volt (V/V), the CSA gain in volts/amp can be computed using Equation 9.
For example, in a system with CSAGAIN = 0.15V/A and ADC Offset Voltage of 1.65V , the base current or maximum measurable system current by the ADC is (3.3V -1.65V)/ (0.15V/A) = 11A.
In system with Rsense of 10milli Ohms, CSA gain of 10V/V , ADC Offset Voltage of 0.4125V, the base current is derived as (3.3-0.4125)/(10m * 10) = 28.875A