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LSF0102: Multiple shifter one after the other.

Part Number: LSF0102

Hello,

We have doubt regarding the use of the LSF0102 is our system. Very rarely we have random 'bus hang' beetween the two LSF.

Is our schematic correct ? What could we do to improve reliability ? Can we use multiple LSF as show below ?

Best regards,

Me.

  • Hi,

    It looks like you're translating up from 4V to 5V, then back down to 2.8V.  Why not just translate from 4V to 2.8V?

    The LSF can be used in this way -- are there pull-ups on the SDA-COM lines?

    Also, I would recommend going with a larger pull-up resistor value.  When the system is driving low, the current from all 3 pull-ups on each line will be sinking into the driver. Setting them all to 10k would likely improve V_OL performance and not really impact data rate capability.

    I am currently working on posting a series of videos explaining how the LSF translators work.  I will post a link as soon as I have it completed.

  • Hello Emrys,

    Thank you for your reply.

    Yes we are translating twice the level of the bus. the 4V => 5V is on the final product customer platform and it is mandatory to do that as to get the same voltage as the power supply of the D.U.T for the customer..  The 5V => 2.8V is on the measurement system as it need to be able to get data on 2.8V product. It is a complex system which get measurement from a wide range of product.

    You can see that as a customer product(4->5)  on a test board (5->2.8) on a motherboard on a thermal chamber.

    Yes there are pull-ups at anytime on the COM line ( both line ) and we use the enable as a switch for the I²C.

    On internal side we can manage to change the pull up to a larger value and decrease the current but on the outside ( COM ) we need at least 6mA so we are in conformance with I²C specification for 400Khz bus with very high capacitance load. ( We're reaching around 400pf which is the limit ).

    We are running up to 96 LSF0102 in parrallel and they all act as a giant switch. So most off the time we are in the state were 95 LSF are disabled and one is translating to his internal bus.

    Thank you we would be very happy to get detailled work even if there are already lots of information about this everywhere on the web.

    Best regards,

    Mr BILLEBAULT

  • Hi Mr Billebault,

    I'm happy to announce that we have officially released a series of 8 videos that explain how to use the LSF family of translators in detail. These videos are part of a new training series called "The Logic Minute" and are available here:

    The Logic Minute

    Please let me know if I can be of further assistance.

  • Hum.

    Access Denied

    The course you are trying to access is either no longer available, or you do not have permission to view the course. Please return to the TI Training home page to search/browse additional training.

  • Well, that's bad! I'll talk to my digital marketing team and see why that's happening. I can access it through my phone without logging into my TI account. What country are you accessing the site from?
  • From France !

    Merci ! ;)
  • I updated the link above. It turns out that the link I originally posted was for internal use only - sorry about that!