PIC16F716-I/P View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
PIC16F716-I/P
Microchip Technology
PIC16F716-I/P Datasheet PDF : 126 Pages
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PIC16F716
Figure 7-14 shows an example where the PWM
direction changes from forward to reverse, at a near
100% duty cycle. At time t1, the output P1A and P1D
become inactive, while output P1C becomes active. In
this example, since the turn-off time of the power
devices is longer than the turn-on time, a shoot-through
current may flow through power devices QC and QD
(see Figure 7-12) for the duration of ‘t’. The same
phenomenon will occur to power devices QA and QB
for PWM direction change from reverse to forward.
FIGURE 7-13:
SIGNAL
PWM DIRECTION CHANGE
Period(1)
If changing PWM direction at high duty cycle is required
for an application, one of the following requirements
must be met:
1. Reduce PWM for a PWM period before changing
directions.
2. Use switch drivers that can drive the switches off
faster than they can drive them on.
Other options to prevent shoot-through current may
exist.
Period
P1A (Active-High)
P1B (Active-High)
P1C (Active-High)
P1D (Active-High)
DC
DC
(Note 2)
Note 1:
2:
The direction bit in the CCP1 Control Register (CCP1CON<7>) is written any time during the PWM cycle.
When changing directions, the P1A and P1C signals switch before the end of the current PWM cycle at intervals of
4 TOSC, 16 TOSC or 64 TOSC, depending on the Timer2 prescaler value. The modulated P1B and P1D signals are
inactive at this time.
FIGURE 7-14:
PWM DIRECTION CHANGE AT NEAR 100% DUTY CYCLE
Forward Period
t1
Reverse Period
P1A
P1B
P1C
P1D
DC
External Switch C
External Switch D
Potential
Shoot-Through
Current
Note 1:
2:
3:
All signals are shown as active-high.
ton is the turn-on delay of power switch QC and its driver.
toff is the turn-off delay of power switch QD and its driver.
DC
ton
toff
t = toff - ton
DS41206A-page 44
Preliminary
2003 Microchip Technology Inc.
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