A ON SELECT
A OFF SELECT
B ON SELECT
B OFF SELECT
EGEN A
EGEN B
EDGE GEN
PWM A
PWM B
B SELECT
A SELECT
INTRAMUX
A/B/C (N)
A/B/C (N+1)
C (N+2)
C (N+3)
A(N)
B(N)
A(N+1)
B(N+1)
DPWMC, Edge Generation, IntraMax
50
SNIU028A – February 2016 – Revised April 2016
Copyright © 2016, Texas Instruments Incorporated
Digital Pulse Width Modulator (DPWM)
2.11 DPWMC, Edge Generation, IntraMax
The UCD3138 has sophisticated hardware for generating complex waveforms beyond the simple DPWMA
and DPWMB waveforms already discussed. The DPWMC, the Edge Generation Module, and the IntraMux
play a key role in delivering this capability.
DPWMC is a signal inside the DPWM logic. It goes high at the Blanking B begin time, and low at the
Blanking B end time.
The Edge Gen module takes DPWMA and DPWMB from its own DPWM module, and the next one, and
uses them to generate edges for two outputs. For DPWM3, the DPWM0 is considered to be the next
DPWM. Each edge (rising and falling for DPWMA and DPWMB) has 8 options which can cause it. The
options are:
•
0 = DPWM(n) A Rising edge
•
1 = DPWM(n) A Falling edge
•
2 = DPWM(n) B Rising edge
•
3 = DPWM(n) B Falling edge
•
4 = DPWM(n+1) A Rising edge
•
5 = DPWM(n+1) A Falling edge
•
6 = DPWM(n+1) B Rising edge
•
7 = DPWM(n+1) B Falling edge
The Edge Gen is controlled by the DPWMEDGEGEN register. It also has an enable/disable bit.
The IntraMux is controlled by the Auto Config registers. The IntraMux takes signals from multiple DPWMs
and from the Edge Gen. It can be programmed to route these signals to the DPWMA and DPWMB
outputs. This is useful for complex topologies like Phase Shifted Full Bridge, especially when they are
controlled with automatic mode switching. It is disabled by setting the Intramux to Pass Through mode for
each of the DPWM signals, A and B. If the Intra Mux is enabled, high resolution must be disabled.
Here is a drawing of the Edge Gen/Intra Mux:
Figure 2-13. UCD3138 Edge-Gen & Intra-Mux