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Looking for CAN Switch IC

Ray Vincent Aranzaso
Genius 13515 points
Other Parts Discussed in Thread: TMUX1209, TMUX6209, TMUX7209

Hi,

Good Day. I have a customer who wants a CAN Switch IC. I hope you can help him to find one that fits for his wants. Please see below his query for your reference. Thank you very much.

i need a CAN Switch IC. i am trying to find in TI website but in vain. I don't have the part number. My requirement is, i have CANH and CANL signals, i should be able to connect these two signals with  multiple IC CANH and CANL signals like De-mux

Best Regards,

Ray Vincent

  • 0
    TI__Mastermind 43295 points

    Hi Ray,

    I am a bit confused exactly what the customer is looking for since CAN is multipoint so you shouldn't need a mux/switch.

    But do you possibly have a block diagram of how they are trying to implement it, this includes the following information:

    1. switch configuration (1:1 , 2:1 , 4:1, 8:1 or other (typically multi-chip solution if higher configurations are needed, we have a few 16:1's as well))

    2. how many channels (I'd assume 2 since its differential, but there are a few different options depending on configuration)

    3. Voltage supply available to the multiplexer

    4. Max Signal Level at switch inputs w.r.t. ground -  This should should include the differential voltage as well as the common mode - as typically the mux itself only cares about voltage w.r.t. ground and not common mode specifically

    5. Connection diagram - can be super basic without much detail - just more so high level where is the CAN signal being switched too.

    I don't think you need a mux in the vast majority of CAN systems as they are multi-point, but if the switch is needed in the application could you please provide the above information so I can see what switches we can suggest - as we do have switches that can handle CAN protocol - but depending on the system requirements and what the switch needs to do within the system will dictate if we a device right for the specific application.

    Please let me know the above and  I will see if we have a suitable solution.

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Genius 13515 points

    Hi Parker,

    Good Day. Please see below the response of our customer to your reply. Thank you very much.

    Hi. I have attached the block diagram for your reference. Could you please suggest the IC based on this.

    Best Regards,

    Ray Vincent

  • 0 in reply to Ray Vincent Aranzaso
    TI__Mastermind 43295 points

    Hi Ray,

    We potentially have some options. 

    At a 5V supply, we currently only have parts that will accept/pass  up to 5V w.r.t. ground. Sometimes CAN signals can have a higher common mode voltage which causes inputs to be above the 0V - 5V range - even though the differential part of the signal is. So there would need to be something compensating for higher possible bus voltages. CAN transceivers a lot of time can handle these high common modes with 3.3V or 5V supplies but at the moment we don't have  mux that can.

    That being said we have two potential pathways of a solution - 

    Use a MUX rated for 5V - but need to have external circuit to handle common mode voltages that would cause mux to go out of spec to prevent damage.

    If this is the pathway you want to choose than a device like the TMUX1209 which is a 4:1, 2 channel device. It can accept and pass 0V to VDD and can handle the bandwidth requirements of CAN.  It has three control pins (two select lines and and enable). It also has low on resistance which is important since CAN has a low impedance termination. 

    However if there are higher common mode voltages that cannot be addressed before the 5V switch - than a higher voltage switch is what our next option is. Devices such as the TMUX6209 and TMUX7209 (2 channel 4:1 Mid-Voltage Multiplexers) when used with higher voltage supplies (such as +/- 15V) they will be able to handle common mode voltages as well as the differential. For these parts too be used they need to be used with higher supply voltages because at lower supplies they will be more resistive. So the benefit of this solution is the CAN signal chain isn't changed and the mux can handle it, the issue is that you need higher voltage supplies to make sure the devices can not only handle possible common mode but also to keep its channel parameters optimal  so that data isn't lost during transmission.

    These device's will switch CAN_H and CAN_L signals to 1 of 4 possible options.

    If you have any other questions please let me know!

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Genius 13515 points

    Hi Parker,

    Good Day. Please see below the response of our customer to your reply. Thank you very much.

    "Does the MUX TMUX1209 will support CAN FD also or not??. If not could you please suggest a mux which can support CAN and CAN FD."

    Best Regards,

    Ray Vincent

  • 0 in reply to Ray Vincent Aranzaso
    TI__Mastermind 43295 points

    Hi Ray,

    The TMUX1209 is a passive switch - it does not care about protocol or what the data is. It only cares about voltage, current, and temperature requirements not being violated - so for the 1209 that means it can pass 0V to VDD and has a max VDD of 5.5V. It can pass a max current of +/-30mA. As I said above the 1209 will work if the voltage w.r.t. ground never exceeds 5.5V and the current due to the low differential signal levels of the CAN bus shouldn't be violated. 

    For the application itself - you need to pay attention to bandwidth - considering CAN has very low data rates the 125MHz bandwidth can handle it.

    The options I listed above are the ones best suited for the application.

    Best,

    Parker Dodson