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TPS51631A: Conversion voltage range: operation from 5V?

Victor Puertas Pelaez
Prodigy 30 points
Part Number: TPS51631A

We intend to use TPS51631A to convert from 5V to 1.8V.

In the datasheet it is said that conversion voltage range goes from 4.5 to 28V. Regarding VBAT, recommended operating conditions are -0.1V to 28V.

However, there is the following sentence in page 33 of the datasheet: "VBAT does not have a UVLO function, so the circuit operates with power inputs as low as approximately 3xVout".

From that sentence, we understand that VBAT should be at least 3 x 1.8V = 5.4V. What is the relationship between VOUT and VBAT? Would the circuit work with VBAT = 5V? Can you confirm if operation with VBAT = 5V is possible for VOUT = 1.86V maximum?

Do you have any reference design with conversion voltage / VBAT = 5V? All reference designs that we have seen apparently convert only from 9V-20V.

Thanks in advance

  • 0
    TI__Guru**** 191445 points
    Let me forward your request to the IMVP team.
  • 0
    TI__Intellectual 1790 points
    Hi,
    The Statement in Page33 "VBAT does not have a UVLO function, so the circuit operates with power inputs as low as approximately 3xVout". is true when we use all 3 phases and limited by phase overlap: the phases should not be overlapped so the max duty cycle((1/3)=33%) is limited.

    The VBAT=5V, VOUT=1.8V is possible for two/single phase mode, but not possible in 3phase mode.

    So, Please answer the following questions.
    1. What is the max load current?
    2. How many phases are active in this application?

    We do have reference designs with VBAT=5V.
  • 0 in reply to Rama Pamidi
    Prodigy 30 points

    Hi Rama,

    about this sentence: "VBAT=5V, VOUT=1.8V is possible for two/single phase mode, but not possible in 3phase mode".

    Looking at the design example of page 33 of the datasheet, there are the following parameters: Number of phases = 3, Input voltage range = 5V to 20V, VPS0 = 1.8V.  Should it say then Input voltage range = 6V to 20V? By the way, could we have access to the mentioned Excel spreadsheet tool for component value calculation?

    About your questions.

    We are using the TPS51631A to power the Intel Core-i7 Gen5 E5850EQ. Currently from 12V with 3 phases, but evaluating the possibility to power it from 5V.

    TDP is 48.6W (1.8V@27A), PL2 is 56.1W (1.7V@33A). Maximum current could be 85A.

    Do you think we could operate with two phases? Could we have access to those reference designs with VBAT = 5V?

    Regards

  • 0 in reply to Victor Puertas Pelaez
    TI__Intellectual 1790 points

    Hi Victor,

    Agreed. Datasheet needs to update as input voltage range 6V to 20V.

    The Excel spreadsheet tool for component value calculation  can be sent to you. so please provide your mail id.

    For 85A max. load current, we need 3 phases.

    would you please provide some more details of application.

    1. what is the min and max input voltage?
    2. What is the application(Notebook or server..etc)?
    3. what is the max. load at 5V input, (or)  are 3 phases operating at 5V input.

    Thanks.

    Regards,

    Ramasiddaiah. 

  • 0 in reply to Rama Pamidi
    Prodigy 30 points

    Hi Rama,

    Could you please send the excel spreadsheet and also VBAT=5V reference designs to the next e-mail address? 

    Victor.Puertaspelaez@intl-mission.mrcy.com 

    Notice that 85A max is required for only 10ms. They should be provided by the capacitors. Real maximum current expected for all phases should be 33A for PL2. 

    Next the answers:

    1. Minimum input voltage should be 4.75V. Maximum 12.6V

    2. Application. Single Board Computers in VPX/XMC format for embedded applications.

    3. 33A. There should be 2 phases operating at 5V.

    Regards

    Victor