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SPI Mux/Decoder/Expander

Gabriel Garza45
Intellectual 2275 points
Other Parts Discussed in Thread: SN74LV4051A, CD4097B, SN74CBTLV3251, SN74CBTLV3257

Hello,

Do we have any solutions that would fit this customer criteria?

"I have an SPI bus that is able to select 8 slave chips to write to (the chip select or CS lines are: CS0, CS1,....CS7). This is for an array that has 30 amplitude control chips (HMC 1119 from analog devices), and 30 phase control chips (MAPS 010163). I will write to the chips using the bus as the Master with SPI protocol, i.e., the 60 chips will be written serially one at a time.
The problem is, 8 chip select lines can be connected to only 8 chips. I am looking for a part in between the 8 pins and the 60 chips such that I could wire the 8 lines to the input of the part and wire the output of the part to the 60 chips to enable them uniquely."
Thanks,

  • 0
    TI__Intellectual 2900 points
    Hello Gabe,

    If SPI master's driving strength is capable of handling 60 SPI slaves, what you need is to multiplex CS0~CS7. Using 8 unit of SN74CBTLV3251 or SN74LV4051A, 1:8 de-multiplexer, or 4 unit of CD4097B, 2-channel, 1:8 de-multiplexer, should be enough.


    If SPI bus load capacitance is too high for 60 SPI slaves, a bus isolation device will be recommended.

    For example, if one SPI bus can only support up to 30 devices, technically, 1 unit of SN74CBTLV3257 can be considered to split 60 SPI slaves into 2 groups.