• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 48 subscribers
  • Views 1114 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

THS7353 and I2C bus latch-up issue

Rob Mitrunen
Expert 1685 points
Other Parts Discussed in Thread: THS7353, THS7313, THS7303, THS7373, THS7368, THS7327, TS3V340

My customer asks:

If the power supply is allowed to come up to ~250mV, then the circuit is turned on the THS7353 jams the I2C bus interface on the SDA line (pin 12).  It's like it has come to the conclusion it should be driving its output.  If clocks are provided it eventually lets go of the bus.  Page 37 of the datasheet specifies having a single clock to avoid an issue, but adjusting our firmware to provide that single clock resulted in the issue being even more prevalent.

Leftover from earlier development, our circuit provides some extra I2C clocks at power up, I've attached scope shots of the problem in action when these extra clocks are issued (the first activity on the bus after power-up is this shot).  the top trace is SDA, and the bottom is SCL.  "bus behavior just after turn on.jpg" illustrates what's expected to happen, and "Bus latchup at turn on.jpg" illustrates the issue.  If the THS7353 is lifted, the problem goes away so I am certain the SDA line is being driven by the THS7353 at this time.  Also, the output waveform is not consistent, but the shot of the latchup is the most typical."

"bus behavior just after turn on.jpg" illustrates what's expected to happen:

"Bus latchup at turn on.jpg" illustrates the issue

  • 0
    TI__Expert 3030 points

    Rob ,

    The THS7353 datasheet is in process of being updated and this is one of the areas that is being revised. Until then,  I think it makes the most sense to look at the THS7303 datasheet - page 39 - "I2C Design Notes: Issues and Solutions" section of the Applications portion in the datasheet. This information is applicable to the THS7353 and the THS7313 parts as they used the same fundamental digital section.

    If after reviewing this information there are still questions/concerns then please write back on this forum and I will help out as much as possible.

    Cheers,

    Randy Stephens

  • 0 in reply to Randy S
    Prodigy 90 points

    Hello,

    We are facing the same issue with THS7373.

    Can you please suggest any TI part having same functionality and pin compatibility but without this I2C issue?

    Regards,

    Ankit

  • 0 in reply to Ankit Thakkar
    Prodigy 90 points

    Sorry for the mistake.

    We are facing the same problem with THS7303 and THS7353.

    Please suggest any other device having same functionality but with I2C issue.

     

    Regards,

    Ankit

  • 0 in reply to Ankit Thakkar
    TI__Expert 3030 points

    Ankit,

    As a previous post shows, I recommend to look at the THS7303 I2C Apps section as it is fully applicable to the THS7353 and THS7303. It points out solutions to the I2C issue.

    As for alternatives, it really depends on what functions you are trying to achieve. solutions could range from using THS7327 (where the I2C does not have issue) to using a THS7368 combined with a switch like the TS3V340 in front. But, it really depends on what features/functions you require in your system. Please let me knwo and I will do my best to help out.

    Cheers,

    Randy

  • 0 in reply to Randy S
    Prodigy 90 points

    Randy,

    Thanks for your prompt reply.

    We are using low pass filters and fixed gain amplifier inside THS7353.

    We require a drop in replacement for THS7353 with exactly the same functionality as THS7353.

    The part you suggested THS7327 is having same functionality but not a drop in replacement.

    Regards,

    Ankit