Chapter 25 FlexPWM
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
695
25.8.8
Deadtime insertion logic
shows the deadtime insertion logic of each submodule, which creates non-overlapping
complementary signals when not in independent mode.
Figure 25-44. Deadtime insertion and fine control logic
While in the complementary mode, a PWM pair can be used to drive top/bottom transistors, as shown in
.
When the top PWM channel is active, the bottom PWM channel is inactive, and vice versa.
NOTE
To avoid short-circuiting the DC bus and endangering the transistor, there
must be no overlap of conducting intervals between top and bottom
transistor. However, the transistor’s characteristics may cause its
switching-off time to be longer than its switching-on time. To avoid the
conducting overlap of top and bottom transistors, deadtime needs to be
inserted in the switching period, as illustrated in
The deadtime generators automatically insert software-selectable activation delays into the pair of PWM
outputs. The deadtime registers (DTCNT0 and DTCNT1) specify the number of IPBus clock cycles to use
for deadtime delay. Every time the deadtime generator inputs change state, deadtime is inserted. Deadtime
forces both PWM outputs in the pair to the inactive state.
PWMA
from Force
Out logic
PWMA
rising
edge
detect
down
counter
start
DTCNT0
zero
PWMB
detect
edge
falling
counter
down
start
DTCNT1
zero
to Output
logic
0
1
IPOL
1
0
INDEP
0
1
0
1
INDEP
0
1
INDEP
0
1
DBLEN
PWMB
0
1
DBLPWM