UCD3138ARMHT datasheet(33/83 Pages) TI

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Start of Period

Period Counter

Start of Period

Filter Period

Adaptive Sample Trigger A

Sample Trigger 1

DPWM Output A

DTC Adjustment

Filter Duty ± 2 x Event 1

Event 1

2 x Event 1

DTC Adjustment

Event 1

DPWM Output B

Blanking A Begin

Blanking A End

Blanking B Begin

Blanking B End

Phase Trigger

Sample Trigger 2

To Other

Modules

To Other

Modules

Filter controlled edge

Adaptive Sample Trigger B

UCD3138A

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SLUSC66B – MARCH 2015 – REVISED MAY 2015

6.5.3

DPWM Resonant Mode

This mode provides a symmetrical waveform where DPWMA and DPWMB have the same pulse width. As

the switching frequency changes, the dead times between the pulses remain the same.

The equations for this mode are designed for a smooth transition from PWM mode to resonant mode, as

described in Section 6.7.2. The diagram of this mode is shown in Figure 6-3.

The Filter has two outputs, Filter Duty and Filter Period. In this case, the Filter is configured so that the

Filter Period is twice the Filter Duty. So if there were no dead times, each DPWM pin would be on for half

of the period. For dead time handling, the average of the two dead times is subtracted from the Filter Duty

for both DPWM pins. Therefore, both pins will have the same on-time, and the dead times will be fixed

regardless of the period. The only edge which is fixed relative to the start of the period is the rising edge of

DPWM A. This is the only edge for which the blanking signals can be used easily.

Events which change with DPWM mode:

•

DPWM A Rising Edge = Event 1

•

DPWM A Falling Edge = Filter Duty – Event 1

•

Adaptive Sample Trigger A = Event 1 + Filter Duty + Adaptive Sample Register or

•

Adaptive Sample Trigger B = Event 1 + Filter Duty/2 + Adaptive Sample Register

•

DPWM B Rising Edge = Filter Duty + Event 1

•

DPWM B Falling Edge = Filter Period – Event 1

•

Phase Trigger = Phase Trigger Register value or Filter Duty

Events always set by their registers, regardless of mode:

•

Sample Trigger 1, Sample Trigger 2, Blanking A Begin, Blanking A End, Blanking B

•

Begin, Blanking B End

Figure 6-3. Resonant Symmetrical Closed Loop

Detailed Description

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