ADV
ANCEINFORMA
TION
TMS320F28377S, TMS320F28376S, TMS320F28375S, TMS320F28374S
SPRS881A – AUGUST 2014 – REVISED JUNE 2015
5.9.4
High-Resolution Pulse Width Modulator (HRPWM)
The HRPWM combines multiple delay lines in a single module and a simplified calibration system by using
a dedicated calibration delay line. For each ePWM module there is one HR delay line.
The HRPWM module offers PWM resolution (time granularity) that is significantly better than what can be
achieved using conventionally derived digital PWM methods. The key points for the HRPWM module are:
•
Significantly extends the time resolution capabilities of conventionally derived digital PWM
•
This capability can be utilized in both single edge (duty cycle and phase-shift control) as well as dual
edge control for frequency/period modulation.
•
Finer time granularity control or edge positioning is controlled via extensions to the Compare A, phase,
and period registers of the ePWM module.
NOTE
The minimum HRPWMCLK frequency allowed for HRPWM is 60 MHz.
NOTE
When dual-edge high-resolution is enabled (high-resolution period mode), the PWMxB output
is not available for use.
5.9.4.1
HRPWM Electrical Data and Timing
shows the high-resolution PWM switching characteristics.
Table 5-60. High-Resolution PWM Characteristics
PARAMETER
MIN
TYP
MAX
UNIT
Micro Edge Positioning (MEP) step size
(1)
150
310
ps
(1)
Maximum MEP step size is based on worst-case process, maximum temperature and minimum voltage. MEP step size will increase
with low voltage and high temperature and decrease with voltage and cold temperature.
Applications that use the HRPWM feature should use MEP Scale Factor Optimizer (SFO) estimation software functions. See the TI
software libraries for details of using SFO function in end applications. SFO functions help to estimate the number of MEP steps per
SYSCLK period dynamically while the HRPWM is in operation.
120
Specifications
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