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LMP7721 not working

Ignat Zhivon
Prodigy 10 points

Other Parts Discussed in Thread: LMP7721

Hello,

This is my first time I am working with LMP7721.  We both two chips. First we send for (machine) soldering (soldering was performed on SMD/DIP adapter).  Then we connected the chip on breadboard as follower(buffer). The chip did not worked.

Second chip we soldered by hand in the same SMD/DIP adapter, and repeated the measurement. Again not  working.

As I have experience working with operational amplifiers I, think I follow the general requirements for soldering (overheating) and electrostatic protection.

Are there some special requirements handling this chip?

What else could be wrong?

Thank you!

  • 0
    TI__Guru 67986 points

    Hello Ignat,

    What "SMD/DIP" adapter are you using?

    Remember that the LMP7721 has a special pinout. It is NOT a standard single pinout.

    Otherwise, there is no special handling required for the LMP7721, other than proper cleaning to preserve the femtoamp current specifications.

    Regards,

  • 0 in reply to Paul Grohe
    Prodigy 30 points

    hi everybody

    what is meant by proper cleaning.

    thanks in advance

  • 0 in reply to oushta oushta
    TI__Guru 67986 points

    Hello Oushta,

    "Proper Cleaning" means a full scrubbing and flush wash with alcohol, followed by a full dry and bake.

    It is more than just a flush with water.

    You need to get the flux and other contaminates washed off first. Just rinsing "water-soluable" flux off still leaves behind a film that can attract dust and moisture. You need to remove all flux and oils that would collect dust and moisture. Spray-on flux remover can leave behind a thick film if not properly rinsed-off afterwards.

    A proper cleaning starts with a standard wash with water and a blow-dry (and bake, if possible), then a scrubbing with isopropyl alcohol, followed by a blow-dry, then a flush with the alcohol, then another blow-dry and then baking to evaporate any residual moisture.

    The alcohol should be blown or wiped off quickly, otherwise it will absorb moisture and leave a nasty white film behind.

    Be sure to get in between and under the pins of the device. This is where the cleaning residues tend to "hide" and collect. It is just like brushing your teeth as you also need to get in between and behind the pins, not just the surface. Be sure to also flush under the devices.

    Note that you really just need to critically clean the input stage area - you don't really have to clean the rest of the circuit (output side, power supplies, following stages, etc.) Any time anything in the input stage is changed, or touched, it should be re-cleaned. Store the board in a sealed bag with a desiccant.

    You can watch me properly clean the LMP7721 board here:

    http://focus.ti.com/general/docs/video/Portal.tsp?langId=en&entryid=0_65zy5r36

    Regards,