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ISO1450: Equivalent circuit use for making Optical Docking System

Electro Guy
Prodigy 10 points
Part Number: ISO1450
Other Parts Discussed in Thread: ISO1540, ISO1640,

The purpose of this circuit request, is to create a i2c connection between 2 devices, where the space between the 2 devices is a (NO FLY ZONE)..

I want to build a circuit that is functionally the same as the ISO1540 i2c opto-isolator, but where the 2 halves are on opposite sides of a glass window that no connections can pass through. The 2 circuit boards will be 1 to 2 CM apart, but nothing physical must cross the gap between them.

They will be inside an enclosed metal box that has multiple devices less than 3 inches apart, where each device will be using the same (Optical docking system)
(The plug-in units have their own connector, but there is No physical space for a second connector.)

The backplane will have TCA9548 multiplexer connected side A of the (Optical Dock)
and plugin modules will have side B of the (Optical Dock)

How do I make an equivalent circuit to the ISO1540, where each half is on separate boards?

  • 0
    TI__Mastermind 31365 points

    Hello Electro Guy (cool name), 

    A really interesting application here. It looks like you are discretely implementing isolation and it looks like it will work. What is the level of isolation needed between two sides? What is the reason you are not simply using an isolator? ISO1640, for example is capable of isolating grounds up to 5kVrms. 

    Also, from your description, it sounds like you are not using a TI device. I can really only assist you if you are using a TI device, so please let me know if you have specific questions regarding the use of ISO1540. That being said, you can use an I2C transceiver (like ISO1540) with an LED driver to power the LED's. 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 10 points

    ooops, I keep saying ISO1450...  I mean ISO1540

    You mentioned a i2c driver that can connect the i2c to the optical side of my  circuit.. That would be the solution I am asking for.. I do not need electrical isolation. I only need physical isolation described below.

    I need a chip that is the equivalent to one side of the ISO1540 that can drive an external LED output and can read an external optical transistor input.... That would reduce my circuit to one chip between the i2c and the (LED/Transistors) on the inner edges sof the 2 PCBs in my picture. That is what I am asking for...

    Hi Andrew, I am trying to connect lab equipment to the internet. Tektronix makes a lab rack system that comes in 2 versions. TM5006 has an HPIB interface, the TM506 does not.. I am trying to make  i2c substute for HPIB..  The problem with the original design is, if you plug a HPIB plug-in into a TM506 box, you will break the connector. That is why  I said the space between the 2 devices is a (NO FLY ZONE)

    My only thought is how to connect the 2 units without a physical connection bridging the gap...

    Since the 2 devices are both enclosed in metal, then RF link (like NFC) is not possible..

    POGO pins or a magnet connector requires that I have to know exactly where the line I must not cross is... So my only solution is to send the link over light through an open air gap that is wider than the space between the 2 devices.

    So what I need is a circuit that is the working equivalent of the ISO1450, but on separate boards like the example in my picture.... The closest circuit I know of that might work is a MIDI interface.

    One question I have about the original ISO1450 is, how can it send data from one side to the other without the other side sending it right back as an endless loop?

  • 0 in reply to Electro Guy
    Prodigy 10 points
    Electro Guy said:
    ISO1540

    What I need is the functional equivalent to one half of the ISO1540...

    I need a chip that takes i2c in and converts the data to external LED/OptoTransistors for 2 way i2c over optic data transfer..

    What chip is the equivalent to splitting the ISO1540 in half, Where the optic part is outside the chip?

  • 0 in reply to Electro Guy
    TI__Mastermind 31365 points

    Electro Guy, 

    Electro Guy said:
    One question I have about the original ISO1450 is, how can it send data from one side to the other without the other side sending it right back as an endless loop?

    We continently have an FAQ on this: (+) [FAQ] Why is the logic LOW level output voltage, VOL1, up to 0.8V on Side1 of the ISO1540/ISO1541 and ISO1640/ISO1641 bidirectional I2C isolators?

    Electro Guy said:

    What I need is the functional equivalent to one half of the ISO1540...

    I need a chip that takes i2c in and converts the data to external LED/OptoTransistors for 2 way i2c over optic data transfer..

    What chip is the equivalent to splitting the ISO1540 in half, Where the optic part is outside the chip?

    You can find TI's non-isolated I2C drivers here I2C general-purpose I/Os (GPIOs) product selection | TI.com. I also believe this device may be good for your application. TPIC2810 data sheet, product information and support | TI.com. 

    Please note that if you need further support on either of these product categories, I would recommend starting a new E2E thread with one of these parts in the title so it can be assigned to the team that specializes in these parts.  

    Best,
    Andrew