Pulse 280 Specifications download pdf (Page 23)

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Operational Description of HRPWM

Example 4. SFO Function Calls

main()

{

// User code

// Case1: ePWM1,2,3,4 are running in HRPWM mode

SFO_MepEn(1); // Each of these of function enables

SFO_MepEn(2); // the respective MEP diagnostic logic

SFO_MepEn(3); // and returns MEP Scale factor value

SFO_MepEn(4);

MEP_ScaleFactor1 = MEP_ScaleFactor[1]; // used for ePWM1

MEP_ScaleFactor2 = MEP_ScaleFactor[2]; // used for ePWM2

MEP_ScaleFactor3 = MEP_ScaleFactor[3]; // used for ePWM3

MEP_ScaleFactor4 = MEP_ScaleFactor[4]; // used for ePWM4

// Case2:ePWM1,2,3 only are running in HRPWM mode.

One of the ePWM channel(as an example ePWM4) is used as for

Scale factor calibration

// Here minimum duty cycle limitation is 3 clock cycles.

// HRPWM 4 MEP diagnostics circuit is used to estimate the MEP steps

// with the assumption that all HRPWM channels behave similarly

// though may not be identical.

SFO_MepDis(4); // MEP steps using ePWM4

MEP_ScaleFactor1 = MEP_ScaleFactor[4]; // used for ePWM1

MEP_ScaleFactor2 = MEP_ScaleFactor1 // used for ePWM2

MEP_ScaleFactor3 = MEP_ScaleFactor1 // used for ePWM3

MEP_ScaleFactor4 = MEP_ScaleFactor1 // used for ePWM4

2.5 HRPWM Examples Using Optimized Assembly Code

The best way to understand how to use the HRPWM capabilities is through two real examples:

1. Simple buck converter using asymmetrical PWM (i.e. count-up) with active high polarity.

2. DAC function using simple R+C reconstruction filter.

The following examples all have Initialization/configuration code written in C. To make these easier to

understand, the #defines shown below are used. Note, #defines introduced in TMS320x280x Enhanced

Pulse Width Modulator (ePWM) Module Reference Guide (literature number SPRU791) are also used.

Example 5 This example assumes MEP step size of 150 ps and does not use the SFO library.

SPRU924F– April 2005– Revised October 2011 High-Resolution Pulse Width Modulator (HRPWM)

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Pulse 280 Specifications Page 23