• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 30 subscribers
  • Views 670 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS570LC4357: Power Management Module vs clock domain

Eric Chan Tave
Prodigy 220 points
Part Number: TMS570LC4357

Is it possible to have some additional information on how the PMM (power management module) works?

In the reference manual, section 5.1, it said that “Turning off a domain has the effect to only turn off the clocks into the domain.” But when I look at the datasheet section 6.6.2.2 the clock domains and the power domain does not necessarily match. So, what is the link between the power domain and the clock domain?

  1. Let say Power domain (PD) 6 is turned off.  PD6 switches domain ePWN, eCAP and eQEP to off. However, VCLK3 goes to ePWN, eCAP and eQEP but also to EMIF and Ethernet. So which clock does the PD6 turn off?
  2. Let say PD4 is turned off. If VCLKA2 is turned on after, will the PMM detect an error?

I am asking the question in the context of DO-254 DAL A development where unused functions need to be properly deactivated.

Thank you

  • 0
    TI__Guru**** 197036 points
    Hi Eric,

    There is no one-to-one relationship between power domain and clock domain. For example, the clock domain VCLK3 is mapped to power domain 6 (ePWM, eCAP, and eQEP) and power domain 5 (Ethernet and EMIF).

    If P6 is turned off, the VCLK3 paths to eCAP/ePWM/eQEP are disabled, but the VLCK3 to EMIF and ethernet is still on. To turn off P4, you do not have to turn off VCLKA2, just disable the VCLKA2 to modules in P4.
  • 0 in reply to QJ Wang
    Prodigy 220 points

    QJ Wang said:

    There is no one-to-one relationship between power domain and clock domain. For example, the clock domain VCLK3 is mapped to power domain 6 (ePWM, eCAP, and eQEP) and power domain 5 (Ethernet and EMIF).

    If P6 is turned off, the VCLK3 paths to eCAP/ePWM/eQEP are disabled, but the VLCK3 to EMIF and ethernet is still on. 

    Does this mean that there is “a switch” between the clock domain and clocks into the domain that are managed by the PMM?

  • 0 in reply to Eric Chan Tave
    TI__Guru**** 197036 points
    Hi Eric,

    We can think of it as a gate which is controlled by the PMM power domain clock enable/disable register.
  • 0 in reply to QJ Wang
    Prodigy 220 points

    From what you are saying, my understanding is that the power domain and the clock domain are two independent mechanisms. So, by disabling both (although not necessary and when feasible), the probability of having an erroneous activation of a module is reduced. That should also reduce the probability of detecting a power domain failure (CCM-R5F - Power Domain monitor error (Group 2 Channels 28)). Are my interpretations are correct?
    Thank you

  • 0 in reply to Eric Chan Tave
    TI__Guru**** 197036 points

    Hello Eric,

    Your understanding is absolutely correct. The clock domain and power domain are two independent mechanisms. Please note that:

    In this device, a power domain can operate in one of the three possible power states: ON, IDLE and OFF. ON state is the normal operating state where clocks are actively running in the power domain. When clocks are turned off, the dynamic current is removed from the power domain. In this device, both the IDLE and OFF states have the same power characteristic. When put into either the IDLE or the OFF state, only clocks are turned off from the power domain. Leakage current from the power domain still remains. Note that putting a power domain in the OFF state will not remove any leakage current in this device.