Texas Instruments UCD3138 Technical Reference Manual page 40

DPWM Normal Mode
Cycle Adjust A can be used to adjust pulse widths on individual phases of a multi-phase system. This can
be used if current balancing is necessary, for example. The Adaptive Sample Triggers can be used to
sample in the middle of the on-time (Adaptive Sample Trigger B - for an average output during on-time), or
at the end of the on-time (Adaptive Sample Trigger A - to minimize phase delay). The Adaptive Sample
Register provides an offset from the center or end of the on-time for DPWM signal from the chip. This can
compensate for external delays, such as FET and gate driver turn-on times.
The Blanking signals are used to disable the CBC fault signal during noise. Generally the noise is caused
by DPWM edges. The Blanking registers hold fixed values, so they are easiest to use with fixed edges,
rather than with edges that change dynamically. So in this case, the rising edge of DPWM A and the
falling edge of DPWM B are easy to provide blanking for. In this mode, both blanking times act on the
falling edge of A, since this is what the Cycle By Cycle logic works on.
Cycle Adjust B has no effect in Normal Mode.
In Normal Mode, the DPWM calculated rising edge of DPWMB must not be
permitted to exceed DPWM Event 4. This can be done either with a clamp on
the filter output, or by using an appropriate KCOMP value in the filter output
multiply operation. If this is not done, the DPWMB on time may overlap the
DPWMA on time, causing shoot through
40
Digital Pulse Width Modulator (DPWM)
CAUTION
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SNIU028A – February 2016 – Revised April 2016
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