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TPS76901-HT Output voltage range

Other Parts Discussed in Thread: TPS76901-HT, TPS7H1201-HT, TPS76901-EP

Good Day.  The TPS76901-HT datasheet says that the TPS76901-HT should only be used to a maximum output of 4.5 V and has a absolute maximum input of 13.5 V.  The regular low temperature version of the part is rated to a maximum of 5.5 V out and has an absolute max input of 10V.  Both parts have an Absolute Maximum Output (and FB Voltage) of 7 V. 

A previous discussion ("TPS76901 Output voltage range", 

http://e2e.ti.com/support/power_management/linear_regulators/f/321/t/296672.aspx)

stalled 5+ months ago with the comment "  I am still working on tying to find out the information that you have requested as to what is the limiting factor that dictates output voltage be limited to 4.5V for the -HT part and 5.5V for the standard commercial part.  Will advise as soon as I have a concrete response to it."

I would like to re-open this question specifically for the HT version of the part.  I need a reasonable and available part (i.e. not the TPS7H1201-HT) and would like to understand what limits the TPS76901-HT from use at 5.0 Volts.

Thank you in advance for your thoughts.


Andrew

  • TPS76901-HT  as highlighted in the datasheet

    1.Recommended input voltage is from 5V to 10Vdc.   and Output voltage is 1.2V to 4.5Vmax.

    2. Feedback network which is used to adjust the drive to PMOS (pass element) when characterized over temperature range specified (-55C to 210C)  and process variations limits the maximum output voltage to 4.5V.  This is tested and guranteed per TI qualification of the part.

       As temperature increases leakage current  of internal circuiary would also increase this also limits the output voltage to 4.5V  for reliable applicaton.

    3. Enable pin - active low ensures that the parts turns on over the specifictions highlighted in the datasheet.

    4.  Max rating of the Output and Feedback pins are limited to 7V absolute max.

    5. What is the input voltage/  output voltage and operating temperature in your application?

    5. For low temperature applications up to 125C  standard version TPS76901  will exhibit wider output voltage and is tested and characterized to meet the higher output voltage.

    6.  It is recommended for high temperature applications 200C  for Vout =5V  using TPS7H1201-HT  which is also a PMOS based LDO and rated for 0.5A max  with low dropout voltage would be a viable solution.  This part has been characterized and qualified for High temperature applications as indicated in the datasheet.

     

  • Hi Ramesh - thank you for looking into my question. 

    My current application is to operate to an ambient temperature of 175°C.  Intended input voltage is 5.1 V or a fraction higher if the dropout requires. 

    Is it possible that the TPS76901-HT operation to 150°C could be spec'd the same as the

    TPS76901-EP i.e. for TJ = –55°C to 150°C Vout = 0.97*nominal min to  1.03*nominal max

    , vs. the -HT part          TJ = –55°C to 125°C Vout = 0.95*nominal min to 1.03*nominal max

                                            TJ = 175°C Vout = 0.84*nominal min to 1.03*nominal max ?

    I appreciate that the TPS7H1201-HT is better specified than the TPS76901-HT.  It is also

    • harder to find stocked at distributors
    • available in only 1 lead-formed package (HKS), reducing sourcing options through multi-footprint design
    • costs 4 times as much as the TPS76901-HT
    • has double the pin count of the TPS76901-HT
    • lacks a footprint and detailed thermal mount recommendations in the datasheet
      • is it acceptable to place the HKS package above the PCB thermal pad described in the datasheet, with no thermal material between the lid of the part and the PCB thermal pad?
      • the 2.5 x 2.5 inch PCB thermal pad recommended is obviously much larger than the component.  A footprint recommendation would be very helpful.
    • lacks a footprint or thermal mount recommendations in the package documentation at http://www-s.ti.com/sc/psheets/mcdf013c/mcdf013c.pdf
    • for the lead-formed HKS package the thermal pad is facing away from the PCB
      • is a heat sink required?
      • will this configuration be acceptable when potted in material with poor thermal characteristics?

    For these reasons I would rather not use the TPS7H1201-HT unless the TPS76901-HT is totally impractical.  If some of the unknowns that come with the TPS7H1201-HT are cleared up it would help make it a more attractive component.

  • Hello Andrew,


    I really appreciate your question here, because I am now stuck in the completely same scenario/question than you :)

    I also looked forward to use the TPS76901-HT as an linear regulator at very high temps, but I can not use it

     for my needed 5V supply rail. I also looked at the TPS7H1201-HT which was mentioned here as a replacement,

     but in my oppinion depending on the type of application this is not a viable replacement part at all...I mean

    a Quiescent of max. 28uA (TPS76901-HT, at 175deg-C) vs.  TPS7H1201-HT typical 7mA is totally unacceptable

    for my battery powered application. The regulator would need more current then the whole application circuit together.

     

    Did you find another solution for your application? I would be very thankful for any information or input from

     your side, thank you very much in advance,

     

     Alex

  • Hi Alex, please forgive the delay in my response.  I have ended up "rolling my own" regulator starting from a voltage reference, involving an op amp and ending in bipolars.  Cissoid is a company that offers HT linear regulators and a lot of other HT components but I was not confident of their supply.

  • Hello Andrew,

     I am also very sorry for my so late answer, and thank you very much for your response and the information.

    Shortly after my post  I decided that I will continue to use a switching regulator, and that I will be able to cope with the switching noise on the output. Therefore a linear regulator was not needed anymore for me.

     Thank you again for your answer, have a nice weekend.

  • Andrew,

       Switching regulator will have much higher output noise and will require added external filtering. 

         With regards to characterizing TPS76901-HT for tighter spec limits than what is highlighted in the datasheet will require NRE as  one would have to assign it a separate part number and  special testing would have to be done to guarantee tighter tolerances.

  • Hi Ramesh,

    I appreciate that an LDO would be cleaner than the DC-DC, it just seemed impractical in cost and accuracy.  The question some posts back is still open: is it reasonable that the 150°C maximum component actually has better specifications at 150°C than the -HT version has at only 125°C?  Quoting,

        TPS76901-EP i.e. for TJ = –55°C to 150°C Vout = 0.97*nominal min to  1.03*nominal max,

         vs. the -HT part          TJ = –55°C to 125°C Vout = 0.95*nominal min to 1.03*nominal max

                                               TJ = 175°C Vout = 0.84*nominal min to 1.03*nominal max ?

    It seems odd that at 125°C the TPS76901-HT is looser in tolerance than the TPS76901-EP at 150°C.  The LDO tolerances are so much looser than the DC-DC converter reference and performance specifications that I have found other solutions for the current project.  The other circuit that where I wanted to use the part needed to work with 5 V output so I could not use the -HT component since it was limited to 4.5 V.