Introduction
462
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Enhanced High-Resolution Pulse-Width Modulator (eHRPWM)
16.1 Introduction
16.1.1 Introduction
An effective PWM peripheral must be able to generate complex pulse width waveforms with minimal CPU
overhead or intervention. It needs to be highly programmable and very flexible while being easy to
understand and use. The ePWM unit described here addresses these requirements by allocating all
needed timing and control resources on a per PWM channel basis. Cross coupling or sharing of resources
has been avoided; instead, the ePWM is built up from smaller single channel modules with separate
resources and that can operate together as required to form a system. This modular approach results in
an orthogonal architecture and provides a more transparent view of the peripheral structure, helping users
to understand its operation quickly.
In this chapter, the letter x within a signal or module name is used to indicate a generic ePWM instance on
a device. For example, output signals EPWMxA and EPWMxB refer to the output signals from the ePWMx
instance. Thus, EPWM1A and EPWM1B belong to ePWM1 and, likewise, EPWM4A and EPWM4B belong
to ePWM4.
16.1.2 Submodule Overview
The ePWM module represents one complete PWM channel composed of two PWM outputs: EPWMxA
and EPWMxB. Multiple ePWM modules are instanced within a device as shown in
. Each
ePWM instance is identical with one exception. Some instances include a hardware extension that allows
more precise control of the PWM outputs. This extension is the high-resolution pulse width modulator
(HRPWM) and is described in
. See your device-specific data manual to determine which
ePWM instances include this feature. Each ePWM module is indicated by a numerical value starting with
1. For example ePWM1 is the first instance and ePWM3 is the 3rd instance in the system and ePWMx
indicates any instance.
The ePWM modules are chained together via a clock synchronization scheme that allows them to operate
as a single system when required. Additionally, this synchronization scheme can be extended to the
capture peripheral modules (eCAP). The number of modules is device-dependent and based on target
application needs. Modules can also operate stand-alone.
Each ePWM module supports the following features:
•
Dedicated 16-bit time-base counter with period and frequency control
•
Two PWM outputs (EPWMxA and EPWMxB) that can be used in the following configurations::
–
Two independent PWM outputs with single-edge operation
–
Two independent PWM outputs with dual-edge symmetric operation
–
One independent PWM output with dual-edge asymmetric operation
•
Asynchronous override control of PWM signals through software.
•
Programmable phase-control support for lag or lead operation relative to other ePWM modules.
•
Hardware-locked (synchronized) phase relationship on a cycle-by-cycle basis.
•
Dead-band generation with independent rising and falling edge delay control.
•
Programmable trip zone allocation of both cycle-by-cycle trip and one-shot trip on fault conditions.
•
A trip condition can force either high, low, or high-impedance state logic levels at PWM outputs.
•
Programmable event prescaling minimizes CPU overhead on interrupts.
•
PWM chopping by high-frequency carrier signal, useful for pulse transformer gate drives.
Each ePWM module is connected to the input/output signals shown in
. The signals are
described in detail in subsequent sections.
The order in which the ePWM modules are connected may differ from what is shown in
. See
for the synchronization scheme for a particular device. Each ePWM module consists of
seven submodules and is connected within a system via the signals shown in
.