UCD3138 datasheet(37/68 Pages) TI1

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Start of Period

Period Counter

Start of Period

Period

Sample Trigger 1

DPWM Output A

Filter Duty/2 (High Resolution)

Period/2

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

Triangular Mode Closed Loop

Events which change with DPWM mode:

DPWM A Rising Edge = None

DPWM A Falling Edge = None

Adaptive Sample Trigger = None

DPWM B Rising Edge = Period/2 - Filter Duty/2 + Cycle Adjust A

DPWM B Falling Edge = Period/2 + Filter Duty/2 + Cycle Adjust B

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

Filter controlled edge

Cycle Adjust A (High Resolution)

Cycle Adjust B (High Resolution)

UCD3138

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SLUSAP2 A – MARCH 2012 – REVISED MARCH 2012

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.

4.9

Triangular Mode

Triangular mode provides a stable phase shift in interleaved PFC and similar topologies. In this case, the

PWM pulse is centered in the middle of the period, rather than starting at one end or the other. In

Triangular Mode, only DPWM-B is available. Here is a diagram for Triangular Mode:

Functional Overview

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