TLV3011-EP: Ref output goes up to 3.58v when below -40C on one chip

Aaron Lager

Part Number: TLV3011-EP

We have a TLV3011-EP ( TLV3011AMDBVREP ) where the reference output goes from 1.25v nominal at ambient temperature to about 3.58v when the temperature is less than -40C. We are suspicious as this is our only failure out of about 200 units, and -40C is the lower temperature for the industrial part.

I've read over the thread https://e2e.ti.com/support/legacy_forums/hirel/f/935/p/639438/2386983?tisearch=e2e-sitesearch&keymatch=TLV3011-EP#2386983, and there seems to be a thought that the input V- is sensitive to having ANY positive voltage on it prior the supply voltage coming up. Also there are no clear guidelines on maintaining margin to protect against this behavior as it's not characterized and it varies with temperature.

Our topology is a differential op-amp that that feeds the V- input on the TLV3011-EP. Both amps are powered by the same +5v supply, have the same value bypass caps, and are physically close to each other over a ground plane. The inputs to the diff amp are also powered by the same supply. So the inputs and outputs are at most in sync with the supply as it powers up, but never exceeding the supply.

Is this a bad chip?

over 5 years ago

0 Christian Yots over 5 years ago

TI__Genius 14540 points

Hi,
The engineer supporting this device will get back to you upon his return to the office on Wednesday.

Thanks.

0 Kirby Kruckmeyer96848 over 5 years ago

TI__Genius 17115 points

Hello Aaron,

Please see this post and let me know if it resolves your question:

e2e.ti.com/.../639438

0 Aaron Lager over 5 years ago in reply to Kirby Kruckmeyer96848

Prodigy 85 points

Kirby,

That's the same post that I referenced in my post. No it doesn't solve the problem for us.

See images below for schematic and scope traces of the behavior. From what we can tell, we are not violating the usage of the part.

Traces for first two scope plots:

Yellow: Input to R41 (is a voltage divider based on +5_BIT, R42 is fed by +5_BIT)

blue: output of U11, V- input to U12

purple: output of U12

green: +5_BIT supply

0 Kirby Kruckmeyer96848 over 5 years ago in reply to Aaron Lager

TI__Genius 17115 points

Aaron,

Thank you for the detailed reply.

The other cause we have found for this behavior is if the supply is monentarily taken above the max operating supply spec (5.5V) during power up at cold. Again, this sensitivity is variable from unit to unit. Are you able to monitor the supply voltage at the supply pin?

0 Aaron Lager over 5 years ago in reply to Kirby Kruckmeyer96848

Prodigy 85 points

Kirby,

Yes, in the two upper (individual scope traces), the supply is the green trace (+5_BIT). On the last image, the dual scope plots, it is the yellow trace.

I'll see if I can get a detailed scope trace of the power up behavior of the supply.

Aaron

0 Aaron Lager over 5 years ago in reply to Kirby Kruckmeyer96848

Prodigy 85 points

Just keeping the thread alive. I was on vacation last week. I'm resuming operation/testing on this, this week.

Aaron

0 Kirby Kruckmeyer96848 over 5 years ago in reply to Aaron Lager

TI__Genius 17115 points

Hello Arron,

Since I haven't heard back from you in two weeks, I am going to marked this as resolved.

If you still need help with this, you can reopen it.

Kirby

0 Aaron Lager over 5 years ago in reply to Kirby Kruckmeyer96848

Prodigy 85 points

Sorry for the delay. Here are measurements of the power supply, V- input, ref output (1.25v nominal) and the output (pin 1)

1. Ambient PASS

2. -40C PASS

3. -43C FAIL

For all three the colors are:

green: output pin (for reference only)

red: 5V power

yellow: 1.25v reference output (pin 5)

blue: V- input.

The red and blue traces are placed at the same reference so the power up profile can be observed. The V- input appears to always be less than the power supply.

The 5v power trace reaches 5.21v max overshoot at ambient, and only 5.04v at -43C. So power supply overshoot is not violating the 5.5v max limit.

Please advise.

Aaron

1. Ambient PASS

2. -40C PASS

3. -43C FAIL.

0 Aaron Lager over 5 years ago in reply to Kirby Kruckmeyer96848

Prodigy 85 points

re-opening.

0 Kirby Kruckmeyer96848 over 5 years ago in reply to Aaron Lager

TI__Genius 17115 points

Hello Aaron,

I have sent you a friend request. I will close this thread and you can contact me directly.

Sorry for the delay in response. I have been out of the office and won't be back until Tuesday. in the meantime, I am seeing if someone else can help out on this issue.

Kirby

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TLV3011-EP: Ref output goes up to 3.58v when below -40C on one chip