SLVSEC9C September 2019 – February 2020 DRV8904-Q1 , DRV8906-Q1 , DRV8908-Q1 , DRV8910-Q1 , DRV8912-Q1
PRODUCTION DATA.
The power loss due to the PWM switching frequency depends on the slew rates (rise-time, tRISE_PWM, and fall-time, tFALL_PWM), supply voltage (VVM), motor RMS current (IRMS) and the PWM switching frequency (fPWM). Considering a case, where the PWM switching is only applicable for single half-bridge in a full-bridge configuration (see Free-Wheeling Mode (Synchronous Rectification) Disable / Enable), therefore only half of the half-bridges are operating in PWM switching. Hence, the switching losses during rise-time and fall-time is calculated as shown in Equation 6 and Equation 7.
Putting various parameters from Table 92 in Equation 6 and Equation 7, the rise-time (PSW_RISE) and fall-time (PSW_FALL) switching losses are calculated as shown in Equation 8 and Equation 9 as,
Hence, the total switching power (PSW) is calculated as the sum of rise-time (PSW_RISE) switching losses and fall-time (PSW_FALL) switching losses as shown in Equation 10.
NOTE
The rise-time (tRISE) and the fall-time (tFALL) are calculated based on typical values of the slew rate (SR) from Specifications. This parameter is intended to change based on the supply-voltage, temperature and device to device variation.