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TMS320F280049: One-shot global load

Wayne Huang
Genius 17125 points

Part Number: TMS320F280049

Dear Champs,

I am asking this for our customer.

Please see the following figure using one-shot global load and note "1st" "2nd" "T1" in red.

For LLC topology, for example,

PWM frequency is 14.286us (70KHz) ~ 4us (250KHz)

Control loop is 25 us (40 KHz)

Global load shadow-to-active triggered at PWM TBCTR=0

Questions:

1) GLDCTL2[OSHTLD] = 1 is after 1st Update Shadow Reg. But if 2nd Update Shadow Reg happens on the following shadow-to-active point, does the PWM uses "all of 1st Update Shadow Reg" or "some of 1st Update Shadow Reg and some of 2nd Shadow Reg"?

2) Does the "one-shot" only means to update "once" but not necessarily guarantee the Shadow Registers updated are "only before" GLDCTL2[OSHTLD] = 1?

3) Does the user need to ensure T1 (between two Update Shadow Reg) is larger than the PWM period?

That is, in this case, T1 should be larger than 14.286 us?

  • 0
    TI__Guru 52080 points

    Just going over your settings you have:

    GLDCTL[OSHTMODE] = 1, which means you want to use ONESHOT mode. When you set the GLDCTL2[OSHTLD] = 1, then on the NEXT EVENT in your case CTR=ZERO, the LOAD PULSE is propagated through and ALL of the shadow to active register loads occur.

    There is only one shadow register for each register. So when you double update, it will always use the last written value to the shadow register.

    Setting the OSHTLD = 1, only opens the door for the NEXT EVENT to be able to propagate through, whenever that maybe. It doesnt actually save your setting of shadow register.

    In your case the update will have half of the first setting, and half of the second setting.

    Nima