Looking for a 1:3 SPI Multiplexer

chethan md

Other Parts Discussed in Thread: TMUX1574, SN74LVC139A, TMUX1209

I want to hook up an SPI interface from FPGA to 3 different ADCs in my application, i am using 3 different chip selects from FPGA, with this it might be possible to just short the SPI bus to all 3 ADCs as there are dedicated chip selects, but i am worried about the stub and signal integrity of the SPI bus.

Now thinking to Multiplex the SPI bus coming from FPGA and route it to ADC's.

Is there any device which suits my application?

over 4 years ago

0 Clemens Ladisch over 4 years ago

Guru 269830 points

3:1 muxes are available with one channel or twelve channels. 4:1 muxes are available with one or two channels.

Sorting by price, two two-channel 4:1 muxes might be cheapest.

What frequency and voltage do you need?

0 chethan md over 4 years ago in reply to Clemens Ladisch

Intellectual 840 points

50MHZ and 1.8-3.3V

0 chethan md over 4 years ago in reply to chethan md

Intellectual 840 points

or if dedicated SPI switches arent available, I am planning to use analog switch for example TMUX1574, which is a 4 Channel SPDT, may be i can route SPI bus to ADC1 an dthen place this switch close to ADC1 and then mux to remaining ADC2 and ADC3. OR cascade the TMUX1574 to achieve 3 channel SPI bus switch.

Any comments?

0 Clemens Ladisch over 4 years ago in reply to chethan md

Guru 269830 points

There is no dedicated SPI switch. If you'd wanted a digital device, you would have to use a decoder like the SN74LVC139A, but at 1.8 V, it's probably too slow.

Digital signals can be handled just fine with analog switches, and the direct connection between the pins results in a much higher possible frequency.

To get a list of multichannel 4:1 muxes at 1.8 V, use the search function. You probably want the TMUX1209.

0 chethan md over 4 years ago in reply to Clemens Ladisch

Intellectual 840 points

Okay i got an idea now, may be TMUX1574 suits my application well than TMUX1209.

0 Saminah C over 4 years ago in reply to chethan md

TI__Genius 9132 points

Hi ,

The TMUX1574 is better suited for SPI applications. In addition to supporting SPI signals, it also supports input voltage beyond supply, 1.8V compatible control inputs and powered off protection.

Please let me know if you have further questions.

Thanks

Saminah

0 chethan md over 4 years ago in reply to Saminah C

Intellectual 840 points

Noted, I will go ahead with TMUX1574. Thanks.

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Looking for a 1:3 SPI Multiplexer