Microchip Technology dsPIC33F Family Manual de usuario descargar pdf (Pagina 27)

dsPIC33F

The PWM module has the following features:

• Dedicated time base supports T

CY/2 PWM edge

resolution

• Two output pins (pair) for each PWM generator

• Complementary or independent operation for

each output pin pair

• Hardware dead-time generators for

Complementary mode

• Output pin polarity defined by nonvolatile device

configuration bits

• Multiple output modes:

- Edge-Aligned mode

- Center-Aligned mode

- Center-Aligned mode with double updates

- Single Event mode

• Manual override register for PWM output pins

• Hardware Fault input pins with programmable

function

• Trigger for synchronizing A/D samples and

conversions to PWM timing

• Each output pin associated with the PWM can be

individually enabled

8.3.1 PWM TIME BASE

The PWM time base is provided by a 15-bit timer with

a prescaler and postscaler. The PWM time base can be

configured for four different modes of operation:

• Free-Running mode

• Single-Shot mode

• Continuous Up/Down Count mode

• Continuous Up/Down Count mode with interrupts

for double updates

The Up/Down Counting modes support center-aligned

PWM generation. The Single-Shot mode allows the

PWM module to support pulse control of certain

Electronically Commutated Motors (ECMs).

Table 8-1 lists the frequencies and resolutions that can

be attained as a function of the dsPIC33F device

instruction cycle frequency.

TABLE 8-1: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS, 1:1 PRESCALER

TCY (FCY) PTPER Value PWM Resolution PWM Frequency*

25 ns (40 MHz) 0x7FFF 16 bits 1220 Hz

25 ns (40 MHz) 0x03FF 11 bits 39.1 kHz

50 ns (20 MHz) 0x7FFF 16 bits 610 Hz

50 ns (20 MHz) 0x01FF 10 bits 39.1 kHz

100 ns (10 MHz) 0x7FFF 16 bits 305 Hz

100 ns (10 MHz) 0x00FF 9 bits 39.1 kHz

200 ns (5 MHz) 0x7FFF 16 bits 153 Hz

200 ns (5 MHz) 0x007F 8 bits 39.1 kHz

* PWM frequencies will be 1/2 the value indicated for center-aligned operation.

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