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TMP100 - SDA pin internal short to GND

Jacek Czarski
Prodigy 20 points
Other Parts Discussed in Thread: TMP100

Hello,

Our company started deliveries of a new product to the customers (10 deployed in the field so far). The product uses TMP100 temperature sensor. The other devices on I2C bus are: a Real Time Clock and up to 8 EEPROMs (24C512). Firmware was carefully tested and there are no conflicts, everything works fine.

On two of those units I lost temperature readings and access to other devices on the I2C bus. One of the faulty units, which operated for only few days, was recovered. The problem was traces to the SDA pin of TMP100 - internally shorted to GND. The temperature sensor was replaces and (about 10 days ago) I set-up the unit in our lab. It operates under similar conditions as in the field. So far no failure...

Did anybody encountered similar problem?

Best regards

Jacek Czarski

  • 0
    TI__Mastermind 25080 points

    Jacek,

    This hasn't been observed before. Please keep in touch if you have further problems with a particular device and we can help work through it. 

  • 0 in reply to Chris Featherstone
    Prodigy 20 points

    Hello Chris,

    I'm keeping couple of sensors on test - so far no failures.

    Your specification for the device shows low level of output at 3mA. What is the maximum sink current?

    Timing diagrams for register read function show master-receiver ACK after last byte was read, then stop condition. However, the I2C bus specification states:

    "If a master-receiver is involved in a transfer, it must signal the end of data to the slave-transmitter by not generating an acknowledge on the last byte that was clocked out of the slave. The slave-transmitter must release the data line to allow the master to generate a STOP or repeated START condition."

    I'm following the I2C specification and NACK is generated after reading last byte. Please comment.

    Best regards

    Jacek

  • 0 in reply to Jacek Czarski
    TI__Mastermind 25080 points

    Jacek,

    The maximum sink current that we specify and assure in the datasheet is 3mA. I discussed this with the designer and the the device can easily sink 2x this current. This current is temperature and supply dependent so we suggest keeping the current to 3mA as this is what we can assure. 

    I have tested the TMP100. Our device adheres to the I2C bus specification regarding the NACK from the master. As seen below the TMP100 will operate with either an ACK or NACK. I have also attached the PPT in order to view an image that is clear. 

    TMP100 ACK NACK Test.pptx