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66AK2H12: 66AK2Hxx - Smartreflex: clarification on the K2H EVM smartreflex implementation?

AnBer
Mastermind 31245 points

Part Number: 66AK2H12
Other Parts Discussed in Thread: UCD74120, UCD9244

Team,

I got the feedback from an EVM's user that the Smartreflex might not be working accordingly on the K2H EVM.

I have seen already the below posts that explains why 2 Smartreflex interfaces (ARM side and DSP side for CVDD) are available on the EVM:
https://e2e.ti.com/support/dsp/c6000_multi-core_dsps/f/639/t/411766
https://e2e.ti.com/support/dsp/c6000_multi-core_dsps/f/639/t/395850
And that the EVM's smartreflex topology should not be used on custom board (but rather the data manual and HW design guide should be followed instead).

Still could you please clarify the smartreflex implementation of the EVM?
- Looking at K2H_K2HEVM-HK_SCH_A104_Rev4_0.pdf:
The CVDD rail is showed as 1 single rail but I think that the ARM CVDD and DSP CVDD are separated as 2 UCD74120 are used.
-Are both VCNTLn and VCNTLnT interface functional on the EVM?
Or is only VCNTL (ie the one documented in the data manual) actively used?
-Measuring with a scope the VCNTLn does not show any activities. Why?
-Is smartreflex only implemented on the DSP portion of the CVDD on the EVM? And is the ARM CVDD rail kept at a constant value?

-Has the MCSDK and processor SDK SW some special workarround for the EVM that that would disable smartreflex for CVDD?

Thanks in advance.

Anthony

  • 0
    TI__Guru 65405 points
    Hi Anthony,

    I've forwarded this to the power experts. Their feedback should be posted here.

    BR
    Tsvetolin Shulev
  • 0
    TI__Mastermind 42545 points

    Hi Anthony,

    The K2H EVM was designed before the K2H silicon was completed and characterized. The K2H was originally designed to operate using either a single CVDD SmartReflex supply rail with one VCNTL interface or separate DSP CVDD and ARM CVDDT core supplies with two SmartReflex supply rails and separate VCNTL & VCNTLT interfaces. The latter configuration was included for customers that wanted to achieve the lowest possible power but after characterization of the silicon, it was determined that the power savings wasn't significant enough to justify the use of two supplies. Once that was determined the support for a two SmartReflex supply solution was removed for the documentation for the K2H. 

    -Are both VCNTLn and VCNTLnT interface functional on the EVM? 
    Or is only VCNTL (ie the one documented in the data manual) actively used? 

    Only the VCNTLn interface is functional.


    -Measuring with a scope the VCNTLn does not show any activities. Why?

    The VCNTLT interface must be enabled. Support for that has been removed.

    -Is smartreflex only implemented on the DSP portion of the CVDD on the EVM? And is the ARM CVDD rail kept at a constant value?

    Separate DSP CVDD and ARM CVDDT supplies were originally included in the design of the K2H EVM. Once we decided that these rails should be driven by a single supply, it was too late in the process to modify the EVM. A single UCD74120 could not provided enough current for the combined CVDD rail however, the UCD9244 allowed us to connect the outputs of these two supplies and control them both via the same VCNTL SmartReflex interface. The combined current capability of the two UCD74120 was enough for the single CVDD supply rail found on the EVM. Since the pins previously labeled CVDDT have been renamed CVDD, it is not possible for the ARM portion of the CVDD to fixed while the DSP portion is SmartReflex capable. 

    -Has the MCSDK and processor SDK SW some special workarround for the EVM that that would disable smartreflex for CVDD?

    MCSDK and processor SDK do not control the SmartReflex interface. This is a function of the internal SmartReflex controller which will send the VID for the needed voltage using the VCNTL interface. SmartReflex cannot be disabled and is required for proper operation of the K2H. The use of a fixed power supply solution for the CVDD rail is not supported and we cannot guarantee the operation of the K2H if SmartReflex is not implemented.

    Regards,

    Bill