PIC12F609-I/PQTP MICROCHIP [Microchip Technology], PIC12F609-I/PQTP Datasheet - Page 92

• Manufacturer Part Number: PIC12F609-I/PQTP
• Description: 8-Pin Flash-Based, 8-Bit CMOS Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

PIC12F609/615/12HV609/615
10.4.5
In Half-Bridge applications where all power switches
are modulated at the PWM frequency, the power
switches normally require more time to turn off than to
turn on. If both the upper and lower power switches are
switched at the same time (one turned on, and the
other turned off), both switches may be on for a short
period of time until one switch completely turns off.
During this brief interval, a very high current (shoot-
through current) will flow through both power switches,
shorting the bridge supply. To avoid this potentially
destructive shoot-through current from flowing during
switching, turning on either of the power switches is
normally delayed to allow the other switch to
completely turn off.
In Half-Bridge mode, a digitally programmable dead-
band delay is available to avoid shoot-through current
from destroying the bridge power switches. The delay
occurs at the signal transition from the non-active state
to the active state. See Figure 10-13 for illustration.
The lower seven bits of the associated PWMxCON
register (Register 10-3) sets the delay period in terms
of microcontroller instruction cycles (T
FIGURE 10-14:
DS41302A-page 90
Standard Half-Bridge Circuit (“Push-Pull”)
PROGRAMMABLE DEAD-BAND
DELAY MODE
EXAMPLE OF HALF-BRIDGE APPLICATIONS
CY
or 4 T
P1A
P1B
OSC
).
Preliminary
FET
Driver
FET
Driver
FIGURE 10-13:
P1A
P1B
td = Dead-Band Delay
Note 1: At this time, the TMR2 register is equal to the
(2)
(2)
V+
V-
2: Output signals are shown as active-high.
(1)
td
Pulse Width
PR2 register.
Load
Period
td
EXAMPLE OF HALF-
BRIDGE PWM OUTPUT
© 2006 Microchip Technology Inc.
+
V
-
+
V
-
(1)
Period
(1)