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TL431-Q1: Query on application

Sandeep Varma
Prodigy 140 points
Part Number: TL431-Q1
Other Parts Discussed in Thread: TL431,

Hi,

I could see 10nF Cap between cathode and reference pin in data sheet of TL431(for ex: Image attached). Two questions as follows:
1)  Is it mandatory to have this cap for voltage regulator application?
2) i know vaguely that it is for stability. What is its use exactly?

  • 0
    TI__Expert 8590 points

    Hi Sandeep,

    Sandeep Varma said:
    1)  Is it mandatory to have this cap for voltage regulator application?

    It is not mandatory to have this capacitor for voltage regulation applications within specific devices like this TL431-Q1 device.

    Sandeep Varma said:
    2) i know vaguely that it is for stability. What is its use exactly?

    It is traditionally used between the cathode and ground or the output and ground as a bypass capacitor to eliminate power supply noise.

    Thanks,

    Joshua

  • 0 in reply to Joshua Garcia
    Prodigy 140 points

    Hi,
    I was asking about the Capacitor between Cathode and ref pin (not between Cathode &  ground or cathode & anode) as highlighted in earlier post(green color). i observed this cap in almost all series voltage regulator application. what is its importance ?

  • 0 in reply to Sandeep Varma
    TI__Expert 8590 points

    Hi Sandeep,

    Sandeep Varma said:
    i observed this cap in almost all series voltage regulator application

    This is a shunt voltage reference, our series voltage references are higher precision & lower Iq devices. 

    Sandeep Varma said:
    what is its importance ?

    Implementing this capacitor filters/balances the capacitance and poles that are generated when looking into the BJT from both the base and the emitter eliminating noise and dc offset on the output.

    Thanks,

    Joshua

  • 0 in reply to Joshua Garcia
    Prodigy 140 points

    Hi,
    Thanks for quick reply and understood the explanation. 
    One Final query-- Is there any document explaining the same in detail. If Yes, Please share.

  • 0 in reply to Sandeep Varma
    TI__Expert 8590 points

    Hi Sandeep,
    Unfortunately, no documentation currently exists within the VRS team, but one of our members is actively working on completing an application note that contains this information. I am unsure of the completion date, but I am certain that once it is completed it will be uploaded to the CC dashboard.
    Thanks,
    Joshua