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66AK2E05: SmartReflex AVS implementation using PMBus

Tarang Jindal68
Intellectual 820 points
Part Number: 66AK2E05

Hello,

We want to support AVS using PMBus. 

Query-1

I have read the app note tiduag0 which is given for AVS implementation using PMBus. 

This app note says that I2C1 interface is used to read the VID values and to command the power module over PMBus. 

if I2C-1 is used for the purpose than what is the use of VCL/VD interface in K2E SoC. Why VCL/VD interface can not be used for the same?

Query-2

Also, the i2C1 interface will be active after SoC configuration, so it creates a doubt that - 

AVS CVDD supply should reprogrammed before SoC configuration or after SoC configuration or we can change the CVDD supply at any time ?

As in VCNTL mode, this is required to change just after reset deassertion as VCNTL pins provide VID values just after reset deassertion. 

is there any such limitation in PMBus mode?

Thanks and Regards

Tarang Jindal

  • 0
    TI__Guru**** 161600 points
    Hi Tarang,

    I've notified the design team. Their feedback will be posted here.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    TI__Mastermind 46460 points

    Tarang,

    Query-1:  I have read the app note tiduag0 which is given for AVS implementation using PMBus.  This app note says that I2C1 interface is used to read the VID values and to command the power module over PMBus.  If I2C-1 is used for the purpose than what is the use of VCL/VD interface in K2E SoC. Why VCL/VD interface can not be used for the same?

    Answer:  PMBus control for AVS on the K2E devices is only over I2C1.  The VCL/VD interface was originally intended for this but their are implementation limitations with that interface and support for it was deprecated.

    Query-2:  Also, the I2C1 interface will be active after SoC configuration, so it creates a doubt that - AVS CVDD supply should reprogrammed before SoC configuration or after SoC configuration or we can change the CVDD supply at any time?  As in VCNTL mode, this is required to change just after reset deassertion as VCNTL pins provide VID values just after reset deassertion.  Is there any such limitation in PMBus mode?

    Answer:  The AVS power supply must initialize at the proper rated voltage at power-on.  The K2E device is rated to operate at this voltage while held in reset.  Once the K2E device is released from reset and starts booting, the AVS driver must be executed to set the proper operational voltage.  This must occur soon after reset release and before any application processing occurs.  Also, since this device supports Smart Reflex Class 0 with Temperature Compensation, the driver must continue to exist so that changes in temperature can trigger changes in the AVS voltage.

    Tom

  • 0 in reply to Tom Johnson 16214
    Intellectual 820 points

    Hello Johnson,

    As you stated - "PMBus control for AVS on the K2E devices is only over I2C1.  The VCL/VD interface was originally intended for this but their are implementation limitations with that interface and support for it was deprecated."

    Ques -  if we want PMBus support with I2C-1 interface, In this case, we do not want to provide support for VCL/VD interface. so can we just provide a Pull up to VCL/VD interface unlike K2E EVM?

    with this statement - "This must occur soon after reset release and before any application processing occurs."

    Ques - After reset release and before app processing, there is a state of SoC Configuration. so, you want to say that, AVS implementation should be done immediate  after SoC configuration.

    Regards

    Tarang

  • 0 in reply to Tarang Jindal68
    TI__Mastermind 46460 points

    Tarang,

    Q1:  Correct, VCL and VD should be pulled high to minimize leakage current.

    Q2:  I do not fully understand what you mean by device configuration.  I will answer differently.  Normal startup is with BOOTROM executing the  boot mode selected.  This loads an intermediate boot loader such as uboot.  This intermediate boot loader than loads an operating system such as Linux.  The AVS voltage must either be set during uboot or immediately at the beginning of operating system execution or at application startup (if no OS).

    Tom