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LMP7701: Humidity info

Ilya Novikov1
Prodigy 60 points
Part Number: LMP7701

Hello TI !

Is there any information about how the input parameters of this part react to change of humidity level?

Maybe graph like this? 

I have a problem with floating output with hum level near 80% and above. And i want to find out this is the problem with pcb tracing or with LMP7701 itself.

Best regards,

Ilia

  • 0
    Guru 140200 points

    Hi Ilia,

    are you shielding the input terminals of LMP7701 by a guard? Are using a Faraday cage to shield the circuit?

    Can you show your schematic and layout?

    Kai

  • 0 in reply to kai klaas69
    Prodigy 60 points

    Hi, Kai

    Pcb is located inside Faraday cage. I used 2 layer stack FR4. There is no mask and silkscreen on board.  Before LMP7701 we used ada4530 from analog and everything was fine without guard ring. I thought(maybe wrong) in terms of 2 layers FR4 pcb and humidity guard ring is not effective. 

    Ilia.

  • +1
    TI__Guru 63580 points

    Ilya,

    We perform (or qualify by similarity) Moisture Sensitivity Level tests (MSL) and Highly Accelarated Stress Test (HAST) on all of our products including LMP7701 but we do not test our parts for the change of specific parameters at different relative humidity levels - they just must pass the datasheet electrical min/max limits and package must have no sign of delamination.  

    Moisture sensitivity level relates to the packaging and handling precautions for some semiconductors. The MSL is an electronic standard for the time period in which a moisture sensitive device can be exposed to ambient room conditions (30 °C/85%RH at Level 1; 30 °C/60%RH at all other levels).

    Moisture/reflow sensitivity classification for plastic[1] Integrated circuit (IC) SMDs, there are eight levels of moisture sensitivity. Components must be mounted and reflowed within the allowable period of time (floor life out of the bag).

    • MSL 6 – Mandatory Bake before use
    • MSL 5A – 24 hours
    • MSL 5 – 48 hours
    • MSL 4 – 72 hours
    • MSL 3 – 168 hours
    • MSL 2A – 4 weeks
    • MSL 2 – 1 year
    • MSL 1 – Unlimited

    Both packages of LMP7701 (SOIC and SOT-23) are classified as MSL 1

    Below are the conditions for testing to Level 1 MSL.

    CSAM

    1. 24 hour bake at 125C
    2. 85C/60%RH for 168 hours
    3. 3 passes of reflow at a peak temp of 260C
    4. Flux submersion/DI water clean
    5. Electrical test
    6. Post CSAM

    Level 1 indicates parts are Not Moisture Sensitive.

    LMP7701 packages are also qualified under 130°C/85% RH HAST test 

  • 0 in reply to Ilya Novikov1
    Guru 140200 points

    Hi Ilia,

    can you explain how the circuit works? Are pin 3 and pin 4 swapped over by mistake?

    Kai

  • 0 in reply to kai klaas69
    TI__Guru 63580 points

    Ilya, Kai has a point that your circuit would not work the way it is shown because of its positve feedback (feedback must be negative).  This is true unless there is another inversion in the signal path that you do not include on your schematic. If there is nothing else, you need to swap connections to pin 3 and 4 (see below) or DOUT will be stuck at one of the rails (at 5V or -5V).

  • 0 in reply to Marek Lis
    Prodigy 60 points

    Hi Kai and Marek.

    Thanks for your help. Because that image was from last revision, where i try to laminate fr4 by ro4350 and that mistake appears only in last prot revision.

    And all previous revisions was fine and these inputs in right positions. 

  • 0 in reply to Ilya Novikov1
    TI__Guru 63580 points

    Good to know you are not trying to use a positve feedback... ;)