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the CVDD voltage of the type of CYG2 and CYG4?

shigehiro tsuda
Mastermind 9490 points

Hi,

In 5.3 Recommended Operating Conditions of the data sheet of DM8168, there is a description as follows.

There is following difference in the supply voltage specifications of CVDD by a device type name.
1.Initial Startup min VINITnom *0.95 nom 1.00 or 1.05 max VINITnom *1.05

2.AVS run-time CYGA2 & CYG4： min SRnom *0.95 nom 0.85-1.00 max SRnom *1.05

3.AVS run-time CYG & CYG2： min SRnom *0.95 nom 0.85-1.05 max SRnom *1.05

note: The initial CVDD voltage at power on must be 1.00V nominal (for CYGA2 and CYG4 devices) or 1.05V nominal (for CYG and CYG2
devices) and it must transition to the AVS target value adjusted by a AVS driver. This is required to maintain full power functionality and
reliability targets specified by TI.

Will you teach why fast device becomes the low voltage?
I think that there are many things which need the high voltage whenever I work at high frequency with other processors of TI.
Are these specifications right?

Best Regards,
Shigehiro Tsuda

  • 0
    TI__Guru**** 170625 points
    Footnote 4 does allow for designs to use the higher startup voltage as stated in Rev E but that it is no longer a requirement. You can get more info from your local TI FAE.

    BR
    Pavel
  • 0 in reply to Pavel Botev
    Mastermind 9490 points

    Hi Pavel,

    Thank you for an answer.
    I see.
    I wil confirm it in local TI FAE.

    Best Regards,

    Shigehiro Tsuda

  • 0 in reply to shigehiro tsuda
    TI__Mastermind 46460 points

    Tsuda-san,

    There are multiple topics here.  You noted the following:

    1.  Initial Startup :                                      min VINITnom *0.95     nom 1.00 or 1.05      max VINITnom *1.05

    2.  AVS run-time CYGA2 & CYG4：        min SRnom *0.95          nom 0.85-1.00          max SRnom *1.05

    3.  AVS run-time CYG & CYG2：            min SRnom *0.95          nom 0.85-1.05          max SRnom *1.05

    Note: The initial CVDD voltage at power on must be 1.00V nominal (for CYGA2 and CYG4 devices) or 1.05V nominal (for CYG and CYG2
    devices) and it must transition to the AVS target value adjusted by a AVS driver. This is required to maintain full power functionality and
    reliability targets specified by TI.

    AVS on DM816x will operate an individual device at the lowest possible voltage that is guaranteed to operate at the rated speed.  it is also guaranteed to operate below the maximum power limits for that speed grade device.

    Power supply tolerance is +/-5%.  Unfortunately, the RevD Datasheet did not capture that well in the spec for the CVDD voltage.  It listed a range of voltages.  This was actually the range of nominal voltages.  The tolerance had to be added on top of these limits.

    CYGA2 (extended temperature) and CYG4 (higher speed) devices operate at higher current consumption levels.  We had to limit the available AVS voltage range to keep the devices within a temperature range that was controllable for reliability issues.  This limit is enforced through screening.

    The initial startup voltage is a single voltage where all devices are guaranteed to operate.  However, due to increased power consumption and heating, they must not be operated at full processing load at this voltage.  The AVS driver will be activated as soon as Linux starts running and this driver will adjust the AVS voltage to the required AVS operating voltage prior to launching the application.

    Tom

  • 0 in reply to Tom Johnson 16214
    Mastermind 9490 points

    Hi Tom-san

    Thank you for quick reply and  detailed explanation.

    I can understand that the fast device such as CYGA2 (extended temperature) and CYG4 (higher speed) worked with the low voltage for temperature restrictions and was chosen through screening.
    I thank for your help very much.

    Best Regards,

    Shigehiro Tsuda