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SMBus timeout feature in INA219

Other Parts Discussed in Thread: INA219, DM3730, TMP102

I2C SDA signal hangs low until a power off/on cycle or SCL is manually clocked.  There are seven INA219s on the bus controlled by a DM3730.  One of them appears to be the device hanging SDA low.  The INA219's data sheet references a 28mSecond SMBus timeout.  I would have thought the SMBus timeout feature would force the INA219 to release the SDA signal.    How does the SMBus timeout work?  

jib

  • Jib,

    Is there any chance you can get me a few scope captures of the SCL and SDA lines with respect to power-cycle and 28mS SMBus timeout?

    I'll check and see if SDA is released when SMBus timeout is initiated.
  • Hi Jason;

    Thank you for your quick response.  This is my 3rd try and sending you a response, so I don't know if you received either of the first two tries.

    I tried pasting a Visio diagram into this response using the Paste from Word button, I don't know if its attached somewhere that I can't see.

    I would like to give you more information and will assume that you can see the image.

    The SDA signal hangs low after the bus master issues transaction for a read from 0x55.  0x55 is a invalid address and the result is no ACK.  On a scope plot you can see the master pull the SDA signal low and release it to stop the transaction, but the signal is still be pulled low by another device.  Since both the TMP102 and INA219 have bus timeout feature, we assumed the SDA signal will being pulled low by the LSM330.  We removed U68 to isolate the INA219s from the bus and the SDA signal no longer hangs.

  • Jib,

    Do I understand correctly that this issue is resolved, and not the TMP102 or the INA219?

    Thank you,
    Jason
  • Jason;
    Can we communicate directly with out going though this forum?
    jib
  • The issue is not resolved and likely is the INA219
  • John,

    Ok, my misunderstanding. Yes please email me directly at Bridgmon_Jason@ti.com with the visio files, scope shots, schematics, etc that you weren't able to attach here and we'll get to the bottom of this. I talked to a digital designer a bit about this issue and I think that with a little more info, we can figure out what is expected and what is erroneous.