Texas Instruments TMS320C6745 DSP - Low % Duty Cycle Range Limitation Example When PWM Frequency = 1 Mhz; High % Duty Cycle Range Limitation Example When PWM Frequency = 1 Mhz

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SPRUH91D–March 2013–Revised September 2016
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Enhanced High-Resolution Pulse-Width Modulator (eHRPWM)
14.2.10.5.3 Duty Cycle Range Limitation
In high resolution mode, the MEP is not active for 100% of the PWM period. It becomes operational
3 SYSCLK cycles after the period starts.
Duty cycle range limitations are illustrated in Figure 14-47. This limitation imposes a lower duty cycle limit
on the MEP. For example, precision edge control is not available all the way down to 0% duty cycle.
Although for the first 3 or 6 cycles, the HRPWM capabilities are not available, regular PWM duty control is
still fully operational down to 0% duty. In most applications this should not be an issue as the controller
regulation point is usually not designed to be close to 0% duty cycle.
Figure 14-47. Low % Duty Cycle Range Limitation Example When PWM Frequency = 1 MHz
If the application demands HRPWM operation in the low percent duty cycle region, then the HRPWM can
be configured to operate in count-down mode with the rising edge position (REP) controlled by the MEP.
This is illustrated in Figure 14-48. In this case low percent duty limitation is no longer an issue.
Figure 14-48. High % Duty Cycle Range Limitation Example when PWM Frequency = 1 MHz