DPWM Control Register 2
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SNIU028A – February 2016 – Revised April 2016
Copyright © 2016, Texas Instruments Incorporated
Digital Pulse Width Modulator (DPWM)
2.17.3 Filter Duty Select
The FILTER_DUTY_SEL bit field has 2 bits, selecting from 3 modes. These modes select what value is
sent to the Resonant Duty input of the Filter Duty multiplicand multiplexer. For example, if
LoopMux.FILTERMUX.FILTER0_PER_SEL is set to 0, and the OUTPUT_MULT_SEL bits for Filter 0 are
set to 3, then the FILTER_DUTY_SEL will select the Filter Duty multiplicand. This value will be multiplied
by the output of the filter to scale it appropriately for the DPWM.
Bit Value
Multiplier for Filter Value
Result
0
DPWM Period
Maximum Filter output gives 100% duty cycle
1
Event 2
Maximum Filter output gives Event 2 duty cycle
2
Resonant Duty Register
Maximum Filter output gives value of Resonant Duty Register
3
Not applicable
Mode 2 is used for LLC with Resonant Mode.
2.17.4 IDeal Diode Emulation (IDE) Enable for PWMB
Setting the IDE_DUTY_B_EN bit enables the digital IDE logic to take control of DPWM B. The IDE logic is
used to make sync FETs turn off at the perfect times, emulating an ideal diode (one with lower voltage
drop). See
for more details.
2.17.5 Sample Trigger 1 Oversampling
As mentioned earlier, the DPWM module generates signals to generate a sample trigger in the Error ADC
in the Front End. The DPWMs can also provide oversampling function in co-ordination with the sample
triggers. The SAMP_TRIG1_OVERSAMPLE bit field permits oversampling of 2, 4, and 8 samples in the
Front End. The samples are equally distributed in time, starting at the start of the period, and with the last
sample at the Sample Trigger 1 point.
The values are:
•
0 – 1 sample at the sample trigger time.
•
1 – 1 sample at 1/2 of the sample trigger time, and one at the sample trigger time
•
2 – 4 samples at 1/4, 1/2, 3/4, and full sample trigger time
•
3 – 8 samples at 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8 and full sample trigger
Sample trigger 1 can be used either to trigger a complete cycle with Front End and Filter, or it can be used
for spatial averaging. See
, especially
.
2.17.6 Sample Trigger 1 Mode
In addition to oversampling, Sample Trigger 1 offers several modes of calculation. The
SAMPLE_TRIG1_MODE bit field selects from 4 of these:
•
0 – Sample Trigger is set using Sample Trigger register (DPWMSAMPTRIG1)
•
1 – Sample Trigger = Event 1 + (DUTY/2) + Adaptive Offset where Duty is most recent Filter Duty
•
2 – Sample Trigger = Event 1 + (DUTY/2) + Adaptive Offset where Duty is Filter Duty from last cycle
•
3 – Sample Trigger = Event 1 + DUTY + Adaptive Fixed Offset where Filter Duty is from last
cycle
On the diagrams earlier in this chapter, option 1 is called Adaptive Sample Trigger B, and option 3 is
called Adaptive Sample Trigger A.
The Adaptive Offset comes from the DPWMADAPTIVE register, which is an 11 bit signed register. Without
the Adaptive Offset, the sample trigger will be in the middle of the on-time for DPWMA in Normal and Multi
Modes. The Adaptive Offset is used to correct for system delays in gate drivers, FET turn-on times and
voltage and current sensing circuits. Using the Adaptive Offset properly can put the sample trigger in the
middle of the voltage or current on-time. The adaptive offset register has the same resolution as the
Sample Trigger Register – 16 nanoseconds. The adaptive register, though is not mapped the same. Bit 0
is the first usable bit. See
for more information.