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EVMK2GX: The purpose of TLV707085DQNT, TPS54429 and LP2996A in the schematic ( Regulators other than TPS65911)

user3788809
Intellectual 900 points
Part Number: EVMK2GX
Other Parts Discussed in Thread: LP2996A, TPS65911, TPS54429,

In the schematic EVMK2GX, what's the purpose of TLV707085DQNT, TPS54429 and LP2996A respectively in the schematic? ( Regulators other than TPS65911)

Could you tell me that the reason why EVMK2GX does not consist of only TPS65911?

(In addition, we would like to know whether 66AK2G12ABYT100 could be opareted with only TPS65911 or not.)

  • 0
    TI__Mastermind 42545 points

    Hi,

    The TLV707085DQNT provides 0.85V if the internal LDOs are not used.  You can see that they are not connected to the SoC for the EVM.

    The TPS54429 is used for 3.3V IO for the EVM.  The TPS65911 does provide 3.3V but more current was needed to support the circuitry on the EVM and daughtercards. You will have to do the current analysis for your design to see if the TPS65911 is sufficient. 

    The LP2996A provides the VTT termination voltage and reference voltage for the DDR3.  The VTT is needed for termination of the flyby signals and requires a push/pull power supply as required by the DDR specification.  This voltage is not provided by the TPS65911.  For more information see TPS65911A User’s Guide for 66AK2G12 Processor (Rev. A).

    Regards, Bill

  • 0 in reply to Bill Taboada
    Intellectual 900 points

    Hi Bill,

    Let me comform it.

    >>The TLV707085DQNT provides 0.85V if the internal LDOs are not used.  You can see that they are not connected to the SoC for the EVM.

    →  What is the internal LDOs? Is it in the 66AK? Could you tell me where to check  in the TRM? (how to set whether it is used or not and so on)

    Thanks,

    Fujii

  • 0 in reply to user3788809
    TI__Mastermind 42545 points

    Hi Fujii,

    The internal LDOs are discussed in section 7.3.1.4 of the data manual. The TRM contains some configuration register information for the LDOs but not much information.

    Regards, Bill

  • 0 in reply to Bill Taboada
    Intellectual 900 points

    Hi Bill,

    "66AK includes internal LDOs which generate 0.85V for internal PCIe PHY and USB PHY.

    And whether the internal LDOs are used or not is set by the some configuration register described in TRM.

    If the internal LDO is not used, LDO_PCIE_CAP should be connected to the external 0.85V gereneted by external regulator such as TLV707085DQNT."

    ↑　Is this correct?

    Regards, Fujii

  • 0 in reply to user3788809
    TI__Mastermind 42545 points

    Hi Fujii,

    I do not think I have made myself clear.  The AK2G12 is designed to operate with the internal LDOs enabled.  The registers described in the TRM are loaded from efuse and will be populated with the correct value.  Internal LDOs were new technology for the K2G so the external power supply was added to the EVM design as a precaution.  The external power supply has never been used.  It is not an option that should be considered in your design.  The capacitors should be added as described in the data manual to provide the necessary external capacitance for the LDO but no external supply is needed.

    Regards, Bill