UCD3138ARMHT datasheet(51/87 Pages) TI1

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Start of Period

Period Counter

Start of Period

Period

DPWM Output A

Cycle Adjust A (High Resolution)

Filter Duty (High Resolution)

Event 1

Event 3 ± Event 2 (High Res)

Event 4 (High Res)

DPWM Output B

Blanking B Begin

Blanking B End

Phase Trigger

Sample Trigger 2

To Other

Modules

Filter controlled edge

Sample Trigger 1

Blanking A Begin

Blanking A End

To Other

Modules

Adaptive Sample Trigger A

Adaptive Sample Trigger B

DTC Adjustment

UCD3138A

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SLUSC66C – MARCH 2015 – REVISED SEPTEMBER 2016

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Detailed Description

7.1.1

Normal Mode

In Normal mode, the Filter output determines the pulse width on DPWM A. DPWM B fits into the rest of

the switching period, with a dead time separating it from the DPWM A on-time. It is useful for buck

topologies. The drawing of the Normal Mode waveforms is shown in Figure 7-1.

Cycle adjust A can be used to adjust pulse widths on individual phases of a multi-phase system. This can

be used for functions like current balancing. The Adaptive Sample Triggers can be used to sample in the

middle of the on-time (for an average output), or at the end of the on-time (to minimize phase delay) The

Adaptive Sample Register provides an offset from the center of the on-time. This can compensate for

external delays, such as MOSFET and gate driver turn on times.

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 (DPWMA rising edge). Blanking B could be used at the turn off time of DPWMB.

The other edges are dynamic, so blanking is more difficult.

Cycle Adjust B has no effect in Normal Mode.

Events which change with DPWM mode:

•

DPWM A Rising Edge = Event 1

•

DPWM A Falling Edge = Event 1 + Filter Duty + Cycle Adjust A

•

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 = Event 1 + Filter Duty + Cycle Adjust A + (Event 3 – Event 2)

•

DPWM B Falling Edge = Event 4 + DTC Adjustment

•

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 7-1. Normal Mode Closed Loop

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