Enhanced PWM (ePWM) Module
15.2.2 Functional Description
Seven submodules are included in every ePWM peripheral. There are some instances that include a high-
resolution submodule that allows more precise control of the PWM outputs. Each of these submodules
performs specific tasks that can be configured by software.
15.2.2.1 Overview
lists the eight key submodules together with a list of their main configuration parameters. For
example, if you need to adjust or control the duty cycle of a PWM waveform, then you should see the
counter-compare submodule in
for relevant details.
Table 15-10. Submodule Configuration Parameters
Submodule
Configuration Parameter or Option
Time-base (TB)
• Scale the time-base clock (TBCLK) relative to the system clock (SYSCLKOUT).
• Configure the PWM time-base counter (TBCNT) frequency or period.
• Set the mode for the time-base counter:
–
count-up mode: used for asymmetric PWM
–
count-down mode: used for asymmetric PWM
–
count-up-and-down mode: used for symmetric PWM
• Configure the time-base phase relative to another ePWM module.
• Synchronize the time-base counter between modules through hardware or software.
• Configure the direction (up or down) of the time-base counter after a synchronization event.
• Configure how the time-base counter will behave when the device is halted by an emulator.
• Specify the source for the synchronization output of the ePWM module:
–
Synchronization input signal
–
Time-base counter equal to zero
–
Time-base counter equal to counter-compare B (CMPB)
–
No output synchronization signal generated.
Counter-compare (CC)
• Specify the PWM duty cycle for output EPWMxA and/or output EPWMxB
• Specify the time at which switching events occur on the EPWMxA or EPWMxB output
Action-qualifier (AQ)
• Specify the type of action taken when a time-base or counter-compare submodule event occurs:
–
No action taken
–
Output EPWMxA and/or EPWMxB switched high
–
Output EPWMxA and/or EPWMxB switched low
–
Output EPWMxA and/or EPWMxB toggled
• Force the PWM output state through software control
• Configure and control the PWM dead-band through software
Dead-band (DB)
• Control of traditional complementary dead-band relationship between upper and lower switches
• Specify the output rising-edge-delay value
• Specify the output falling-edge delay value
• Bypass the dead-band module entirely. In this case the PWM waveform is passed through
without modification.
PWM-chopper (PC)
• Create a chopping (carrier) frequency.
• Pulse width of the first pulse in the chopped pulse train.
• Duty cycle of the second and subsequent pulses.
• Bypass the PWM-chopper module entirely. In this case the PWM waveform is passed through
without modification.
1498Pulse-Width Modulation Subsystem (PWMSS)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated