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TMS320F28377S: SFRA Question

user5624527
Intellectual 800 points
Part Number: TMS320F28377S
Other Parts Discussed in Thread: CONTROLSUITE, SFRA

At the BUCK example project of F28377S (C:\ti\controlSUITE\development_kits\BOOSTXL_BUCKCONV\v1_01_00_00\Buck_VMC_F2837xS)

#include "Buck_VMC-Settings.h"
#include "F28x_Project.h"
#define   MATH_TYPE      1   //FLOAT_MATH
#include "DPlib.h"
#include "IQmathLib.h"
#include "SFRA_F_Include.h"
#define SFRA_ISR_FREQ 200000
#define SFRA_FREQ_START 100
#define SFRA_FREQ_LENGTH 100
//SFRA step Multiply = 10^(1/No of steps per decade(35))
#define SFREQ_STEP_MULTIPLY (float)1.0680004
I want to know how does the formula (red mark) come from? Or what "No of steps per decade" means? Why it is 35 in the formula?
  • 0
    TI__Mastermind 43730 points

    It comes from log 10, basically, we want 35 steps in a decade i.e. as frequency goes from 1 to 10, or 10 to 100,

    With some math's if we create a frequency vector that multiplied the frequency point where FRA is performed by 10 ^(1/ no of steps), you will get no of steps in a decade of frequency. 

    This is done because bode is plotted on Log10 scale.. 

  • 0 in reply to Manish Bhardwaj
    Intellectual 800 points
    I am a Chinese, and I don't very understand the parameter of "No of steps per decade". Can you explain more about the meaning of "decade" . Is it mean "ten years" or "Tenfold"? Or other meanings?
    And do you have any instruction documents that can explain it detailed?