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INA240: Offset INA240

Simone Barbabella
Prodigy 20 points
Part Number: INA240

Hello,

I have problem with offset on INA240 amplifier!

I have connected INA240 A2 in the evaluation board and I menasure differential output voltage by a multimeter. With 0 input voltage I measure output voltage 0.6mV more then 25uV in the datasheet!

More, the offset I read is not stable! When I restart the circuit supplay I measure 0.3 mV, a little diffrent Vout! So I can not compensate the initial offsett because it is not stable. 

The same problem I have in my PCB.

With the INA240-A2 origenaly present in the evaluation board I do not have this problem, I read 0.1mV offset, more then 25uV but it is stable on every restart of power supply.

I have this problem with the INA240-A2 purchased from Farnell ! (N. lotto: 7686956ML7)

Someone has encountered by same problem?

Thanks,

Simone

  • 0
    TI__Mastermind 27380 points

    Hi Simon,

     

    Thank you for choosing TI and INA240.

     

    I’ve searched the genealogy of this lot; the parts in your possession are from wafers produced in the beginning of last year.

    We have since identified a power sequence issue. The behavior is similar to what you have observed, ie, the output offset tends to settle to either of two numbers. However, wafers manufactured after mid-2017 have this behavior corrected.

    The issue comes about when the power supply ramps up slowly, at 5V/mS for example. Sometimes it is possible to improve the supply ramp speed so that the issue goes away. Alternatively, we may be able to get you some samples from the new material.

    Regarding the magnitude of the offset, the input offset is 25uV, so the output offset would be ±1.25mV. Any value within this range is normal.

    Regard, Guang

  • 0 in reply to Guang Zhou
    Prodigy 20 points
    Thank you, Guang
    Exactely as you write, I observe the output offset is settled to either two numers!
    I had guessed that power supply ramp could be to affect this behavior, but I did not susseed to find the work around.
    Thank you also for clarification on offset meaning, in fact offset is the input voltage that make zero output voltage, so I agree with you that I can meansure an output voltage +/-25uV*50 =+/-1.25mV .
    I nead to buy INA240-A2 for my first production lot and I want to avoid to purchase a defeting item so I want to learn to read lot numer identification for undestend production time. Can you help me?

    Simone.
  • 0 in reply to Simone Barbabella
    TI__Mastermind 27380 points

    Hi Simone,

     

    I can help look up lot history if you have lot numbers from vendors. It is still cumbersome; however it is probably the only way.

    Can you send me a message and we can take this conversation offline? We can get my other marketing/panning colleagues involved to better bring this to a resolution.

    My email is g-zhou@ti.com

    Regard, Guang