Microchip Technology MA330028 Data Sheet
2011-2014 Microchip Technology Inc.
DS80000533H-page 13
dsPIC33EPXXXGP50X, dsPIC33EPXXXMC20X/50X and PIC24EPXXXGP/MC20X
20. Module: PWM
The PWM generator may not assert dead time on
the edges of transitions. This has been observed
when all of the following conditions are present:
the edges of transitions. This has been observed
when all of the following conditions are present:
• The PWM generator is configured to operate
in Complementary mode with Independent
Time Base (ITB) or master time base;
Time Base (ITB) or master time base;
• Immediate update is enabled; and
• The value in the PDC register is updated in
• The value in the PDC register is updated in
such a manner that the PWMxH and PWMxL
outputs make an immediate transition.
outputs make an immediate transition.
The current duty cycle, PDC
OLD
, newly calculated
duty cycle, PDC
NEW
, and the point at which a write
to the Duty Cycle register occurs within the PWM
time base, will determine if the PWMxH and
PWMxL outputs make an immediate transition.
PWMxH and PWMxL outputs make an immediate
transition if the Duty Cycle register is written with a
new value, PDC
PWMxL outputs make an immediate transition.
PWMxH and PWMxL outputs make an immediate
transition if the Duty Cycle register is written with a
new value, PDC
NEW
, at a point of time when the
PWM time base is counting a value that is in
between PDC
between PDC
NEW
and PDC
OLD
. Additionally,
writing to the Duty Cycle register, close to the
instant of time where dead time is being applied,
may result in a reduced dead time effective on the
PWMxH and PWMxL transition edges.
instant of time where dead time is being applied,
may result in a reduced dead time effective on the
PWMxH and PWMxL transition edges.
In
, if the duty cycle write occurred in the
shaded box, then PWMxH and PWMxL will make
an immediate transition without dead time.
an immediate transition without dead time.
FIGURE 1:
TIMING DIAGRAMS FOR CENTER ALIGNED AND EDGE ALIGNED MODES
Work around
None.
However, in most applications the duty cycle update
timing can be controlled using the TRIGx trigger, or
Special Event Trigger, such that the above
mentioned conditions are avoided altogether.
timing can be controlled using the TRIGx trigger, or
Special Event Trigger, such that the above
mentioned conditions are avoided altogether.
Affected Families and Silicon Revisions
PHASEx
PWMxH
PWMxL
Period
PTMRx
PWMxH
PWMxL
PWMxH
PWMxL
0
PDC
OLD
PDC
NEW
> PDC
OLD
PDC
NEW
< PDC
OLD
Center Aligned Mode
0
PHASEx
PTMRx
Period
PWMxH
PWMxL
PWMxH
PWMxL
PWMxH
PWMxL
PDC
OLD
PDC
NEW
> PDC
OLD
PDC
NEW
< PDC
OLD
Edge Aligned Mode
Immediate
Transition Region
dsPIC33/PIC24EP32 devices
A3
dsPIC33/PIC24EP64 devices
A2, A3, A8
dsPIC33/PIC24EP128 devices
A3, A8
dsPIC33/PIC24EP256 devices
A3
dsPIC33/PIC24EP512 devices
A7