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TLV431B-Q1: maximum voltage

Ross Parlour
Intellectual 1240 points
Part Number: TLV431B-Q1
Other Parts Discussed in Thread: TLVH431B-Q1,

Hi There,

I appreciate the recommended operating voltage max is 6V for the Cathode Voltage in this part, but would there be instability if the part was set to a typical voltage of 6.076V? I see the abs max is 7V in the D/S.

My response to the customer is that "you should not operate outside of the D/S spec. We cannot guarantee any behavior or conditions outside of the spec.", but for my own curiosity, I am keen to understand if this would cause an unstable voltage. 

I am told the worst case scenario would be 6.5V from the customer.

I have already suggested the TLVH431B-Q1 to allow for a wider voltage range.

Many thanks for your time,

Ross

 

  • 0
    TI__Expert 3835 points
    Hi Ross,

    Voltage stability for a shunt reference depends the capacitive load and cathode current as you can see on Figure 19 of the datasheet. Increasing the cathode voltage will change the cathode current depending on the bias resistor.

    Is the worst case scenario 6.5V the supply voltage or reference voltage? Does the customer plan to change the reference voltage in normal operation?

    You are correct in response to the customer and the device recommendation for wider voltage range.

    Regards,
    Ethan
  • 0 in reply to Ethan T
    TI__Intellectual 1240 points
    Hi Ethan,

    These are the customers conditions:
    Series resistor is 1k5.
    Minimum supply voltage = 7 V.
    Maximum supply voltage is 16 V.
    Potential divider = 39k (top); 10k (bottom)
    Voltage set to 6.08 V.
    Worst case max = 6.5 V.
    Current = 0.3 to 6 mA.
    10 nF between K and A.

    They are now considering the TLVH431B-Q1 as this is the safest solution going forward. From my side, I’m just wondering how much risk there is if they did continue to use the TLV431B-Q1. Again, not something from my position I will recommend.

    Thanks again for your help,
    Ross
  • 0 in reply to Ross Parlour
    TI__Expert 3835 points

    Hi Ross,

    Thanks for the update. I would say switching to TLVH431B-Q1 would be the right decision. Designing with headroom is always good engineering.

    Since the absolute maximum of the TLV431B-Q1 is not violated, I would expect the device to be functional. We would not guarantee our datasheet specifications since recommended conditions are violated. If devices failures do occur, then we are also not responsible since recommended conditions are violated.

    Regards,

    Ethan