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LMP91300 serial interface connection

Igor Gorbounov
Expert 1070 points
Other Parts Discussed in Thread: LMP91300

Hi TI team,

using a lmp91300.pdf datasheet only I cannot understand how serial interface could be connected

to this IC. It would be nice if there was some document (application note?) explaining this.

And a more thorough application scheme (diagram?) would be highly helpfull, too.

Best regards,

     Igor Gorbounov

  • 0
    TI__Expert 6550 points

    Hello Igor,

    The LMP91300 uses a bi-directional Single Wire Interface protocol to program and read registers. Since it only contains 1 wire for error free communication, I dont think the block diagram can take place here.  You could refer to multiple open sources or section 7.5 of the datasheet how to program the registers.

    www.google.com/search;sourceid=ie7&rls=com.microsoft:en-us:IE-Address&ie=&oe=&rlz=&safe=active&gws_rd=ssl

    http://en.wikipedia.org/wiki/Single_Wire_Protocol

     Best Regards,

    Natallia Holubeva

     

  • 0 in reply to Natallia Holubeva1
    Expert 1070 points
    Hello, Natalia,
    "... it only contains 1 wire for..." - there is some difficulty with this 1-wireness: the Rx data are transmitted through Sensor2+ pin
    and Tx - through LED pin (or vice versa) - according to datasheet. So how could they be combined into 1 wire? There is a PCB
    layout example in this datasheet but there is no trace of any terminals or points to connect some 1-wire programming hardware.
    Also very little or nothing is said there about nominals of resistors and capacitors for example schemes shown in that datasheet.
    The sample ICs are now shipping to us but I've got no idea about their proper usage - the lmp91300.pcb document is not
    comprehensive enough.
    Best wishes,
    Igor Gorbounov
  • 0 in reply to Igor Gorbounov
    TI__Expert 6550 points
    Hello Igor,

    The datasheet describes how to set the registers and perform write and read operations. Could you please describe me what specific information you are looking for?

    I will get back to you regarding the layout in a couple of days.

    Best Regards,
    Natallia Holubeva
  • 0 in reply to Igor Gorbounov
    TI__Genius 16890 points
    Hi Igor,

    The LMP91300 uses SWIF (Single Wire InterFace) to communicate. The LMP91300 was designed to be used in inductive sensors (see Figures 19 and 20 in the datasheet) which only have three leads coming out so all the communication needs to be done on the power line.
    Talking to the LMP91300 is done by sending a string of 8V to 12V pulses on the power line. The pulses are described in Figure 15 of the datasheet.
    The LMP91300 communicates back to the micro by turning on the LED using the same pulse scheme as shown in Figure 15. This creates a series of current pulses that can be sensed on the power line.
    We have an eval board that has the LMP91300 mounted on it, this is what is shown in Figures 19 and 20. We also have a communication board that shows a way to do all the SWIF communication. This layout can be copied for use in your application.
    Please contact Tarig Chang (tchang@ti.com) for information on getting these boards.

    Mike
  • 0 in reply to Michael Stout
    Expert 1070 points
    Hello Natalia and Michael,
    thank you for your help, now it all looks much clearer.
    I wait from Tarig any help on SWIF implementation in this very application case.
    Best regards,
    Igor Gorbounov
  • 0 in reply to Igor Gorbounov
    TI__Expert 6550 points
    Great,

    He should get back to you soon.

    Best Regards,
    Natallia Holubeva