LTC4332 - How to connect multiple remote slaves

Hi,

I have to connect a local SPI master to multiple remote slaves.

What is the correct way to achieve it?

Can I chain Y/Z of the local to multiple A/B of the remotes and multiple Y/Z of the remotes to A/B of the local and keep only single remote with ON enabled?

Thanks



minor update
[edited by: eyalasko at 4:33 PM (GMT -4) on 2 Oct 2020]
  • 0
    •  Analog Employees 
    on Oct 2, 2020 7:33 PM 1 month ago

    Hi,

    That is an interesting question. 

    You understand correctly that the LTC4332 does not support multidrop networks. The protocol only supports communication between a local and remote LTC4332.

    The remote LTC4332 does have 3 chip select outputs integrated. Does the application need more than 3 SPI slave devices, or to support multiple remotely located PCBs?

    Jason

  • Hi Jason,

    Thanks for your prompt response.

    The application should support 16 or more remote devices (separate devices).

    Can't the remotes share the differential busses with only 1 remote enabled at any time (ON=1) assuming there's a way to set/reset ON signal remotely by other means than the LTC4332

    Thanks again for any advice.

  • +1
    •  Analog Employees 
    on Oct 6, 2020 3:55 PM 1 month ago in reply to eyalasko

    Hi, 

    The LTC4332 pair is designed to service up to 3 remote SPI slaves. I'm not clear if the application needs 16 (or more) physically separate devices plugging in, or if there are 16 (or more) slaves at one location and the limitation is not enough available slave selects...

    If 16 separate remote devices, this would require a pair of LTC4332 to support each remote device. For example, if this were multiple ports for temperature sensors monitoring different positions in a system, each port would require a pair on the local and remote boards. 

    If there are additional slave selects needed at one location, it may be more convenient to remove the LTC4332 and instead add a remote uC and RS485 transceiver, like LTC2862A, to service so many devices. Communication between local and remote would be through the UART rather than the SPI bus. 

    Regards,

    Jason