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TMS320F28376S: High resoultion PWM complementary with deadband enable

Part Number: TMS320F28376S

Dear Sir ,

we are developing controller based on 28376S C2000 chip , and require to symeteric PWM with complementary signals with deadband.

for that purpose i have used  signals A,B of ePWM1  ( i have looked on some example related to PWM) . but the main configuration is

1.PWM in Up Down mode ( Symmetric )

2.High Resoultion mode is enable 

3.dead band is endable to generate complementary signlas based on A

the main issue i see is that the complementary signal is not high resoultion 

 i have Set value to CMPA  and CMPAHR      (PRD =360  , CMPA=340  , CMPHAR=30*256 +0x80  , ePWM CLK = 100Mhz )

and i have looked on ePWM1A and ePWM1B   , indeed ePWM1B is complementary of A  , but it doesnt iclude the high resoultion part  (by the way no DB dealy was added)

is it possiable to generate complementary  high resoultion PWM signlas with deadban enable ?

(by the way setting HRCNFG.SELOUTB to 1  , allow to generate high resoultion complementary signals  ... but without deadband)

  • Yes, but I believe you need to also enable HIGH resolution Deadband.

    Nima

  • Hi Nima,

    thank for the reply , but what i am seeing  is that the complementary signal doesn't have the high resoultion part  (even when i enable dead band high resoultion)

    1. assuming dead band FED and RED are 0 (also the DB high Resoultion register  is 0 )

    2. i have SET CMPA=10%   DC  , and CMPHR to  ~4ns  ( 30  <<8   , ~ 30 *150ps)  , on ePWMA  i can see the effect of high resoultion + Duty cyce in CMPA

       on complementary    (ePWM1B ) can see the inverted signal but without high resoultion part  (the DC ~90%0

    from what i have seent the part that inverts the ePWM1b is the deadband module  , while that part the responsable for high resoultion  comes afterward  , and i think that is the reason why in this configuration i am not able to achive high resoultion complementary signlas with dead band 

    any idea ?

  • Can you try adding the same setting to CMPBHR? CMPBHR is not CMPB but it is for CHANNEL B. 

    I will look into my old HRPWM code and see if there is anything else missing.

    Nima


  • hi Nima ,

    i think you are on the right track , assuming the following setup  , i have modifed the PWM  

    1.Channel A High Resoultion is MEP is set to Rising Edge  (regradless of High resoultion Dead band )

    2. Channel B high Resoultion is MEP is set to Falling Edge   (regradless of High resoultion Dead band )

    3.when issue PWM CMD   , then   CMPA=integer (CMD)    and CMPAHR=CMPBHR=friction(CMD)

        with this i can control PWM in high resoultion on complementary signals (altough i see differnce of 1.2ns between A/B  signals between falling adn rising      edge)

    4.in adtion i have also have control of Dead band in  high resoultion.

    is it look right (meaning every time i update new command i also need to update in addtion to CMPA,CMPAHR  also CMPBHR) ? 

  • Yes I believe that is the case, I have also checked in with other EPWM experts incase this doesnt work for you.

    Nima