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TL1431-EP: Boundary Stability for TL1431-EP

James Azotea
Prodigy 60 points
Part Number: TL1431-EP
Other Parts Discussed in Thread: TL431, TL1431

I have low current voltage reference applications where my A to K current is less than 7mA. It does not see any added circuit capacitance; >= to 0.01uF.  

I series two TL1431-EP shorting Ref to K (Test circuit  "A") with < 7mA. I have a 10V reference using the TL1431-EP in configuration "C".

Will the TL1431-EP oscillate at cold temperature (-55C) using these application conditions? I have had the older part TL431 oscillate at cold temperatures (-55C) thus my question.

The TL1431-EP Stability Boundaries on the Left have no voltage assigned  voltages for the test circuits like in the TL1431 data sheet on the Right.

Is this an improvement in TL1431-EP technology where boundary stability is no longer a function of voltage, configuration, and current or did some one forget to include the voltages as in the TL1431 data sheet?

Pleas advise.

Thanks,

Jim

  • 0
    TI__Intellectual 1695 points

    The TL1431 datasheet is dated Oct 2016 vs the TL1431-EP as Jan 2015. Will need to check if your finding is related to revision history. Will check and report back soon

  • 0
    TI__Intellectual 1135 points
    James Azotea said:
    A to K current is less than 7mA

    I'm assuming you mean K to A.

    James Azotea said:
    I series two TL1431-EP shorting Ref to K (Test circuit  "A") with < 7mA. I have a 10V reference using the TL1431-EP in configuration "C".

    James, can you please send me the circuit diagram for this?

  • 0
    Prodigy 60 points

    Look at Figures 18 and 20 from your data sheet that I attached to this email. Figure 10 (circuit A) shows shorting the ref pin to the cathode pin for a 2.5V reference. Add another 2.5 volt reference in series with the first reference; now you have a 5V temperature stable reference as long as the a-K current is < 7mA according to the data sheet. There is no added capacitance just the parasitic capacitance of the TL1431. Note the older data sheet shows boundary stability as a function of voltage for circuits A-D. You need to look at your data sheet.

  • 0 in reply to James Azotea
    TI__Intellectual 1135 points

    Hi James,

    Are you referring to staking TL1431? If yes, is there any particular reason why you wouldn't use a resistor feedback network and add a large capacitor for stability?

  • 0 in reply to Abhishek Wadhwa
    Prodigy 60 points

    It may be possible to use a divider to provide a 5V reference. I do it for a 10V reference referenced to gnd. The 5V reference is referenced to the positive rail used in a current source circuit. Works great on the proto-board.  Has 1 less part not that that matters much. I can not afford large capacitance in the circuit. The start up time is very quick. I do not have external capacitance across the TL1431 that could make it unstable over a given voltage range. I want to use the extended temperature part an wondered if the stability was still a function of voltage ; not given in the new data sheet with extended temperature range. That is the question I need answered. Also, the Ika current is low making it stable over all voltage ranges. Thanks.

  • 0 in reply to James Azotea
    TI__Intellectual 1135 points

    Hi James,

    That is a fair point. Do you have an graphs/data I can look at to comment on the instability in this scenario?

    Best,

    Abhishek