PIC18F86K90-I/PT Microchip Technology, PIC18F86K90-I/PT Datasheet - Page 261

• Manufacturer Part Number: PIC18F86K90-I/PT
• Description: 64kB Flash, 4kB RAM, 1kB EE, 16MIPS, NanoWatt XLP, LCD, 5V 80 TQFP 12x12x1mm TRA
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F86K90-I/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 64MHz
• Connectivity: I²C, LIN, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 69
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 24x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 80-TQFP
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

19.4.2.1
In the Full-Bridge mode, the PxM1 bit in the CCPxCON
register allows users to control the forward/reverse
direction. When the application firmware changes this
direction control bit, the module will change to the new
direction on the next PWM cycle.
A direction change is initiated in software by changing
the PxM1 bit of the CCPxCON register. The following
sequence occurs prior to the end of the current PWM
period:
• The modulated outputs (PxB and PxD) are placed
• The associated unmodulated outputs (PxA and
• PWM modulation resumes at the beginning of the
For an illustration of this sequence, see Figure 19-10.
The Full-Bridge mode does not provide a dead-band
delay. As one output is modulated at a time, a
dead-band delay is generally not required. There is a
situation where a dead-band delay is required. This
situation occurs when both of the following conditions
are true:
FIGURE 19-10:
 2010 Microchip Technology Inc.
in their inactive state.
PxC) are switched to drive in the opposite
direction.
next period.
Note 1: The direction bit, PxM1 of the CCPxCON register, is written any time during the PWM cycle.
PxA (Active-High)
PxB (Active-High)
PxC (Active-High)
PxD (Active-High)
2: When changing directions, the PxA and PxC signals switch before the end of the current PWM cycle. The
Signal
Direction Change in Full-Bridge Mode
modulated PxB and PxD signals are inactive at this time. The length of this time is:
(1/F
OSC
) • TMR2 Prescale Value.
EXAMPLE OF PWM DIRECTION CHANGE
Pulse Width
Period
Preliminary
(1)
PIC18F87K90 FAMILY
• The direction of the PWM output changes when
• The turn-off time of the power switch, including
Figure 19-11 shows an example of the PWM direction
changing from forward to reverse, at a near 100% duty
cycle. In this example, at time, t1, the PxA and PxD
outputs become inactive, while the PxC output
becomes active. Since the turn-off time of the power
devices is longer than the turn-on time, a shoot-through
current will flow through power devices, QC and QD
(see Figure 19-8), for the duration of ‘t’. The same
phenomenon will occur to power devices, QA and QB,
for PWM direction change from reverse to forward.
If changing PWM direction at high duty cycle is required
for an application, two possible solutions for eliminating
the shoot-through current are:
• Reduce PWM duty cycle for one PWM period
• Use switch drivers that can drive the switches off
Other options to prevent shoot-through current may
exist.
the duty cycle of the output is at or near 100%.
the power device and driver circuit, is greater than
the turn-on time.
before changing directions.
faster than they can drive them on.
Pulse Width
(2)
Period
DS39957B-page 261