MA160014 Microchip Technology, MA160014 Datasheet - Page 194

• Manufacturer Part Number: MA160014
• Description: MOD PLUG-IN 44PIN PIC18LF45K22
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of MA160014

• Accessory Type: Plug-In Module (PIM) - PIC18LF45K10
• Product: Microcontroller Modules
• Data Bus Width: 8 bit
• Core Processor: PIC18LF45K22
• Interface Type: I2C, SPI
• Operating Supply Voltage: 1.8 V to 5.5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PICDEM PIC18 Explorer, DM183032
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

PIC18(L)F2X/4XK22
14.4.2.1
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 four Timer cycles 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
See
FIGURE 14-12:
DS41412D-page 194
in their inactive state.
PxC) are switched to drive in the opposite
direction.
next period.
Figure 14-12
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)
Signal
2: When changing directions, the PxA and PxC signals switch before the end of the current PWM cycle. The
Direction Change in Full-Bridge
Mode
modulated PxB and PxD signals are inactive at this time. The length of this time is (TimerX Prescale)/F
where TimerX is Timer2, Timer4 or Timer6.
for an illustration of this sequence.
EXAMPLE OF PWM DIRECTION CHANGE
Pulse Width
Period
(1)
Preliminary
The Full-Bridge mode does not provide dead-band
delay. As one output is modulated at a time, dead-band
delay is generally not required. There is a situation
where dead-band delay is required. This situation
occurs when both of the following conditions are true:
1.
2.
Figure 14-13
changing from forward to reverse, at a near 100% duty
cycle. In this example, at time t1, the output PxA and
PxD become inactive, while output PxC 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
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:
1.
2.
Other options to prevent shoot-through current may
exist.
The direction of the PWM output changes when
the duty cycle of the output is at or near 100%.
The turn off time of the power switch, including
the power device and driver circuit, is greater
than the turn on time.
Reduce PWM duty cycle for one PWM period
before changing directions.
Use switch drivers that can drive the switches off
faster than they can drive them on.
Pulse Width
14-10) for the duration of ‘t’. The same
(2)
shows an example of the PWM direction
Period
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