• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 278 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLV171: Input current in absolute max table

Oba
Genius 17985 points

Part Number: TLV171
Other Parts Discussed in Thread: OPA990,

Hello,

I want to confirm the meaning of the below yellow marked current spec in the absolute max table.

Screenshot 2025-10-29 104838.png

 

In the data sheet of other part numbers like OPA990 like the below, there is a note which says the inpiut pin voltage can be over if the current is limited to 10mA. 

 

Screenshot 2025-10-29 105020.png

But in the TLV171 datasheet, there is not such a note.
So I just want to confirm if this +-10mA has the same meaning.
Is it OK to input over V+ voltage to input pins if the current is limited to 10mA in TLV171?

In my customer case, a certain voltage may be applied to the input pins during powered-off.
But the current is may be 2uA level.

Regards,
Oba

 

  • 0
    TI__Mastermind 28728 points

    Oba,

    Whenever you see the absolute maximum voltage rating and absolute maximum current rating listed as is shown in the table below, you can add a series resistor in front of the input to limit the current and protect the device.  The series resistor will not only limit the current, but it will also limit the voltage at the input pin.  The reason is that the voltage at the input pin will be one diode drop away from the supply voltage.  In the electrical overstress example below, the input voltage is equal to the supply + Vdiode because there is a forward bias ESD protection diode between the input and supply.  The series resistor limits the current to 10mA or less but also drops voltage to limit the input voltage to a safe value as well.  

    Now, in your case you can add a current limiting resistor to protect the op amp during a power down condition.  However, any voltage applied to the input will be channeled through the ESD diode to the supply.  In some cases, this can power up the device even when power is not applied to the supply pins (i.e. the power is applied from the input through the ESD diodes).  This unexpected power source can sometimes turn on the part and sometimes the device will be in an unexpected mode.  This is because often when the supply is powered in this unexpected way, the supply voltage is out of specification and may remain in this state for extended periods.  I doubt that you will have any problem like this because your current is limited to 2uA.  The bottom line is that we do not recommend applying signals to op amps when they are not powered.  However, if you current limit the input this rarely causes issues, and in your case the current is very small so I think you are ok.   How to Protect Op amps from Electrostatic Discharge & Electrical Overstress Damage  covers this topic in detail.

    I hope this is helpful.

    Best regards, Art

  • 0 in reply to Art Kay
    TI__Genius 17985 points

    Hello Art,

    Thank you very much for your very detail explanation.

    I'm not sure if the customer can put a resistor.

    But basically the input voltage over V(+)+0.5V can be applied to the input pins, meaning not damaged, if the current is limited to less than 10mA. 
    But it could rise the power supply voltage. But 2uA probably will not have so much effect.
    Correct?

    Regards,
    Oba

  • +1 in reply to Oba
    TI__Mastermind 28728 points

    Oba,

    You are correct.  The 2uA should not be an issue (even with no supplies).

    Art