
PIC18F6585/8585/6680/8680
DS30491C-page 180
2004 Microchip Technology Inc.
16.2.4
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 complementary PWM
This mode can be used for half-bridge applications, as
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 PORTE<6> data latches, the
TRISC<2> and TRISE<6> bits must be cleared to
configure P1A and P1B as outputs.
FIGURE 16-5:
HALF-BRIDGE PWM
OUTPUT
FIGURE 16-6:
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.
PIC18FXX80/XX85
P1A
P1B
FET
Driver
FET
Driver
V+
V-
Load
+
V
-
+
V
-
FET
Driver
FET
Driver
V+
V-
Load
FET
Driver
FET
Driver
PIC18FXX80/XX85
P1A
P1B
Standard Half-Bridge Circuit (“Push-Pull”)
Half-Bridge Output Driving a Full-Bridge Circuit