UCD3138 datasheet(33/68 Pages) TI1

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Phase Shift

Phase Trigger = Phase Trigger Register value or Filter Duty

DPWM0 Start of Period

Period Counter

DPWM0 Start of Period

DPWM1 Start of Period

Period Counter

DPWM1 Start of Period

UCD3138

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SLUSAP2 A – MARCH 2012 – REVISED MARCH 2012

Blanking A-Begin and Blanking A-End can be used to blank out noise from the MOSFET turn on at the

beginning of the period (PWMA rising edge). Blanking B could be used at the turn off time of PWMB. The

other edges are dynamic, so blanking is more difficult.

Cycle Adjust B has no effect in Normal Mode.

4.6

Phase Shifting

In most modes, it is possible to synchronize multiple DPWM modules using the phase shift signal. The

phase shift signal has two possible sources. It can come from the Phase Shift Register. This provides a

fixed value, which is useful for an interleaved PFC, for example.

The phase shift value can also come from the filter output. In this case, the changes in the filter output

causes changes in the phase relationship of two DPWM modules. This is useful for phase shifted full

bridge topologies.

The following figure shows the mechanism of phase shift:

Functional Overview

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UCD3138 Datasheet(PDF) 33 Page - Texas Instruments