SPRUHM9H October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
In high-resolution mode, the MEP is not active for 100% of the PWM period and becomes operational:
Duty cycle range limitations are illustrated in Figure 14-86 to Figure 14-89. This limitation imposes a duty cycle limit on the MEP. For example, precision edge control is not available all the way down to 0% duty cycle. When high-resolution period control is disabled, regular PWM duty control is fully operational down to 0% duty cycle despite the unavailability of HRPWM features in the first three cycles. In most applications, this cannot be an issue as the controller regulation point is usually not designed to be close to 0% duty cycle. To better understand the useable duty cycle range, see Table 14-16. When high-resolution period control is enabled (HRPCTL[HRPE] = 1), the duty cycle must not fall within the restricted range; otherwise, there can be undefined behavior on the ePWMxA output.
PWM Frequency(1)
(kHz) |
3 Cycles Minimum Duty |
3 Cycles Maximum Duty(2) |
---|---|---|
200 | 0.6% | 99.4% |
400 | 1.2% | 98.8% |
600 | 1.8% | 98.2% |
800 | 2.4% | 97.6% |
1000 | 3% | 97% |
1200 | 3.6% | 96.4% |
1400 | 4.2% | 95.8% |
1600 | 4.8% | 95.2% |
1800 | 5.4% | 94.6% |
2000 | 6% | 94% |
If the application demands HRPWM operation below the minimum duty cycle limitation, then the HRPWM can be configured to operate in count-down mode with the rising edge position (REP) controlled by the MEP when high-resolution period is disabled (HRPCTL[HRPE] = 0). This is illustrated in Figure 14-87. In this configuration, the minimum duty cycle limitation is no longer an issue. However, there is a maximum duty limitation with same percent numbers as given in Table 14-16.