Datasheet

dsPIC33FJ06GS001/101A/102A/202A and dsPIC33FJ09GS302
DS75018C-page 184  2011-2012 Microchip Technology Inc.
15.2 Feature Description
The PWM module is designed for applications that
require:
• High-resolution at high PWM frequencies
• The ability to drive Standard, Edge-Aligned,
Center-Aligned Complementary mode, and
Push-Pull mode outputs
• The ability to create multiphase PWM outputs
For Center-Aligned mode, the duty cycle, period, phase
and dead-time resolutions will be 8.32 ns.
Two common, medium power converter topologies are
push-pull and half-bridge. These designs require the
PWM output signal to be switched between alternate
pins, as provided by the Push-Pull PWM mode.
A phase-shifted PWM describes the situation where
each PWM generator provides outputs, but the phase
relationship between the generator outputs is
specifiable and changeable.
A multiphase PWM is often used to improve DC/DC
Converter load transient response, and reduce the size
of output filter capacitors and inductors. Multiple DC/
DC Converters are often operated in parallel, but
phase-shifted in time. A single PWM output, operating
at 250 kHz, has a period of 4 s, but an array of four
PWM channels staggered by 1 s each, yields an
effective switching frequency of 1 MHz. Multiphase
PWM applications typically use a fixed-phase
relationship.
A variable phase PWM is useful in Zero Voltage
Transition (ZVT) power converters. Here, the PWM
duty cycle is always 50%, and the power flow is
controlled by varying the relative phase-shift between
the two PWM generators.