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ADC121C021-Q1: DOA? no Pin 1 mark on package, how fragile are the SDA, SCL pins?

Brian Sparano
Prodigy 80 points
Part Number: ADC121C021-Q1

Hi All,

While my boards are out for fab, I'm working on the library to access this ADC.  Unfortunately I cannot get it to respond to any i2c queries (either directly to address 0x54 or by scanning all addreses looking for ACK).  I have the chip on an adapter board in my breadboard at the moment.

I have the SDA, SCL pulled up to 3v with 10k pullups and have the recommended "typical" application circuit breadboarded (except for a 4.7uF ceramic cap instead of tantalum).  

I'm trying to rule out a DOA, static damage, or infant mortality.  I'm working with the 6 pin sot23-6 package and there is no pin 1 marker on the chip.  I set the orientation so that the pin below and left of the start of the marking was pin 1.  Getting no response, I rotated the chip, but I don't know if the SDA and SCL pins can handle the 3v and ground applied to them.

   

Am I missing something obvious here or did I fry the chip? (I got the chip directly from TI as a sample so I'm sure it is genuine.

Thanks

  • 0
    TI__Genius 16890 points
    Hi Brian,

    The way you have the picture drawn is correct. If you are able to read the writing on top, then pin 1 is at the lower left corner of the package. There is also normally on these SOT packages a faint line (it is hard to see and you have to get the light angle just right) that runs along the side of the chip that has pins 1, 2 and 3.

    Putting the part in backwards can destroy the part. I have done that also and it has destroyed the part I was using.

    When you try a new part, can you change the pull up resistors to 5k or even 3k to see how that fixes the problem?

    Mike
  • 0 in reply to Michael Stout
    Prodigy 80 points
    Thanks Mike. I did actually see the line as well with my jewelers magnifier.

    I'll try another part and report back.

    Brian
  • 0
    TI__Prodigy 10 points

    Hi Brian

    I am the Marketing Engineer for this product and was interested to know which end-application you're using this part in.

    Would you mind sharing those high-level details with TI? This helps us improve the part as well as support your needs better.

    My email ID is s-seth@ti.com

    Thanks!

    sachin