PIC16F610 Datasheet, PDF (104/180 Pages) Microchip Technology – 14-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F610/616/16HV610/616
10.4.6 PROGRAMMABLE DEAD-BAND
DELAY MODE
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 10-16 for illustration.
The lower seven bits of the associated PWM1CON
register (Register 10-3) sets the delay period in terms
of microcontroller instruction cycles (TCY or 4 TOSC).
FIGURE 10-16:
EXAMPLE OF HALF-
BRIDGE PWM OUTPUT
Period
Period
P1A⁽²⁾
Pulse Width
td
td
P1B⁽²⁾
(1)
(1)
(1)
td = Dead-Band Delay
Note 1: At this time, the TMR2 register is equal to the
PR2 register.
2: Output signals are shown as active-high.
FIGURE 10-17: EXAMPLE OF HALF-BRIDGE APPLICATIONS
V+
Standard Half-Bridge Circuit (“Push-Pull”)
FET
Driver
+
P1A
V
-
FET
Driver
P1B
Load
+
V
-
V-
DS41288C-page 102
Preliminary
© 2007 Microchip Technology Inc.