
PIC18F2X1X/4X1X
DS39636D-page 144
2009 Microchip Technology Inc.
15.4.4
HALF-BRIDGE MODE
In the Half-Bridge Output mode, two pins are used as
outputs to drive push-pull loads. The PWM output
signal is output on the P1A pin, while the complemen-
tary PWM output signal is output on the P1B pin
applications where four power switches are being
modulated with two PWM signals.
In Half-Bridge Output mode, the programmable dead-
band delay can be used to prevent shoot-through
current in half-bridge power devices. The value of bits
PDC6:PDC0 sets the number of instruction cycles
before the output is driven active. If the value is greater
than the duty cycle, the corresponding output remains
of the dead-band delay operations.
Since the P1A and P1B outputs are multiplexed with
the PORTC<2> and PORTD<5> data latches, the
TRISC<2> and TRISD<5> bits must be cleared to
configure P1A and P1B as outputs.
FIGURE 15-4:
HALF-BRIDGE PWM
OUTPUT
FIGURE 15-5:
EXAMPLES OF HALF-BRIDGE OUTPUT MODE APPLICATIONS
Period
Duty Cycle
td
(1)
P1A(2)
P1B(2)
td = Dead-Band Delay
Period
(1)
Note 1: At this time, the TMR2 register is equal to the
PR2 register.
2: Output signals are shown as active-high.
PIC18F4X1X
P1A
P1B
FET
Driver
FET
Driver
V+
V-
Load
+
V
-
+
V
-
FET
Driver
FET
Driver
V+
V-
Load
FET
Driver
FET
Driver
PIC18F4X1X
P1A
P1B
Standard Half-Bridge Circuit (“Push-Pull”)
Half-Bridge Output Driving a Full-Bridge Circuit