ePWM Submodules
714
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Enhanced Pulse Width Modulator (ePWM) Module
1. By adding S6, S7, and S8 in the figure "Configuration Options for the Dead-Band Submodule" below,
RED and FED can appear on both the A-channel and B-channel outputs. Additionally, both RED and FED
together can be applied to either the A-channel or B-channel outputs to allow B-channel phase shifting
with respect to the A-channel. Note: Phase shifting B-channel with respect to the A-channel using the
Dead band Submodule Additonal Operating Modes has limitations with respect to the choice of RED and
FED delay with respect to the operating duty cycle of the ePWMxA and ePWMxB outputs.
2. The dead-band counters have also been increased to 14-bits
3. Dead-band and dead-band High-resolution registers are now shadowed.
4. High-resolution deadband RED and FED have been enabled using the DBREDHR and DBFEDHR
registers
NOTE:
The PWM-Chopper will not be enabled when high-resolution dead-band is enabled
NOTE:
High-resolution deadband RED and FED requires Half-Cycle clocking mode
(DBCTL[HALFCYCLE] = 1).
Cannot have both RED and FED together applied to both ePWMxA and ePWMxB. RED and
FED together can be applied only to either OutA OR OutB.
NOTE:
Phase shifting B-channel with respect to the A-channel: When PWMxB is derived from
PWMxA using the DEDB_MODE bit and by delaying rising edge and falling edge by the
phase shift amount. When the duty cycle value on PWMxA is less than this phase shift
amount, PWMxA’s falling edge has precedence over the delayed rising edge for PWMxB. It
is recommended to make sure the duty cycle value of the current waveform fed to the Dead
band module is greater than the required phase shift amount.
Shadow Mode:
The shadow mode for the DBRED is enabled by setting the DBCTL[SHDWDBREDMODE] bit and the
shadow register for DBFED is enabled by setting the DBCTL[SHDWDBFEDMODE] bit. Shadow mode is
disabled by default for both DBRED and DBFED
If the shadow register is enabled then the content of the shadow register is transferred to the active
register on one of the following events as specified by the DBCTL[LOADREDMODE] & DBCTL
[LOADFEDMODE] register bits:
•
CTR = PRD: Time-base counter equal to the period (TBCTR = TBPRD).
•
CTR = Zero: Time-base counter equal to zero (TBCTR = 0x00)
•
Both CTR = PRD and CTR = Zero
NOTE:
When DBRED/DBFED active is loaded with a new shadow value while DB counters are
counting, the new DBRED / DBFED value only affects the NEXT PWMx edge and not the
current edge.
NOTE:
If a shadow-to-active load for the DBRED or DBFED registers occurs at the same time as a
corresponding rising or falling edge, then the RED or FED is applied to the PWM signal
before the shadow-to-active load occurs. This causes shadow-to-active loads for the Dead-
band’s RED or FED to not take effect for this event. The value contained within the active
register will take effect for this event; subsequent RED or FED delays will reflect this
shadow-to-active load. Immediate writes to the RED or FED registers are unaffected
7.2.5.3
Controlling and Monitoring the Dead-Band Submodule
The dead-band submodule operation is controlled and monitored via the following registers: