SD multiplexer

Thread Starter

TimoQ42

Joined Apr 20, 2022
3
I designed a SD multiplexer to be able to switch an SD card between two devices inspired by the SD mux. However i want to verify the design before ordering a PCB. To do this i build the circuit on a prototype board, and eventhough all the connections seem te be correct ( as verified with a multimeter ) however there is no connection possible between SD card and host device. My expectation is that this is caused by noise and bounce caused by the imperfections of the prototype and the lack of a groundplane. My supervisor would like me to confirm this before proceding. Would it be possible to have a 240MHz qSPI connection on a prototype board or will i have to move to a PCB anyways?
 

drjohsmith

Joined Dec 13, 2021
401
I designed a SD multiplexer to be able to switch an SD card between two devices inspired by the SD mux. However i want to verify the design before ordering a PCB. To do this i build the circuit on a prototype board, and eventhough all the connections seem te be correct ( as verified with a multimeter ) however there is no connection possible between SD card and host device. My expectation is that this is caused by noise and bounce caused by the imperfections of the prototype and the lack of a groundplane. My supervisor would like me to confirm this before proceding. Would it be possible to have a 240MHz qSPI connection on a prototype board or will i have to move to a PCB anyways?
have you seen this
https://www.onsemi.com/products/interfaces/analog-switches/fssd06
 

Thread Starter

TimoQ42

Joined Apr 20, 2022
3
Thanks for the reply, i'm currently using the TS3A27518EPWR that is also used in the SD Mux found here https://wiki.tizen.org/SD_MUX. The chips does what i want however the communication still fails. The reply from TI is that it might be that the capacitor that i currently use is not suitable to remove the switching noise on the VCC. So i will swap out the capacitor later this week and see if that makes a difference.
 

drjohsmith

Joined Dec 13, 2021
401
Thanks for the reply, i'm currently using the TS3A27518EPWR that is also used in the SD Mux found here https://wiki.tizen.org/SD_MUX. The chips does what i want however the communication still fails. The reply from TI is that it might be that the capacitor that i currently use is not suitable to remove the switching noise on the VCC. So i will swap out the capacitor later this week and see if that makes a difference.
Can you send us a picture of the test board you have ?

Is the mux powered up at the same time / before the sd card is powered up ?
 

Thread Starter

TimoQ42

Joined Apr 20, 2022
3
Hereby the pictures. Currently the mux is always powered because i expected that to be the problem. I also replaced the capacitor in the picture with a 100nF ceramic capacitor but no difference so far.

WhatsApp Image 2022-04-20 at 2.04.15 PM.jpegWhatsApp Image 2022-04-20 at 2.03.54 PM.jpeg
 

drjohsmith

Joined Dec 13, 2021
401
Thats a lot better than I thought you might have
probably the wiring,

test by removing / bypassing the chip
see if it works with one SD card
 
Top