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When MUX is operating at 200MHz @ V+ 1.8V clock signal attenuates below 1V.

Satyaharika Ananthagiri
Prodigy 100 points

Part Number: TS3A27518ETRTWRQ1

Hi,

Im using TS3A27518ETRTWRQ1 device on my board for eMMC and SD card interfaces.

Im using eMMC in below modes the with TS3A27518ETRTWRQ1 device

1. DDR Mode 50MHz at 1.8V eMMC data transfer successful and voltage and clock signals are observed as expected

2.HS200 mode 200MHz at 1.8V eMMC data transfer fails at most of times.

Voltage attenuated to less than 1V (<VIH level) clock is 200MHz.

Please check the attached one.

3.HS400 mode at 200MHz not even device initialized.

Thanks 

Harika.eMMC clock signals.docx

eMMC clock signals at different frequencies

  • 0
    TI__Genius 9132 points

    Hi Satyaharika,

    Thank you for using e2e.

    For digital applications we recommended the switch bandwidth be 1.5 times the datarate per lane or 3 time the clock frequency per lane.  

    The TS3A27518 supports bandwidth of 240MHz.(measured to the frequency that is attenuated -3dB)

    When you are using DDR mode, with 50MHz you have enough bandwidth margin with the TS3A27518.

    However, when you are in HS200 mode with 200MHz clock signal, you need to use a switch higher bandwidth ~ 600MHz. 

    Are you using all 6 channels of the TS3A27518?  

    You can use the TI.com switch selection tool and filter for high bandwidth devices.  For example a 4-channel, 2:1, 1.8V, and >500 MHz bandwidth would return the TMUX1574. For >4 channels the TS5MP645 is good solution.

    I also searched the switches e2e forum typing "eMMC" and found this posting.

    Thanks

    Saminah

  • 0 in reply to Saminah C
    Prodigy 100 points

    Thank you Saminah.

    Before finalized this part we checked this with TI support team.We got confirmation from TI for 200MHz frequency so we proceeded and designed the board.

    Can you please suggest for this debug.

    Regards,

    Harika

  • 0 in reply to Saminah C
    Prodigy 100 points

    Yes we are using all the 6 channels

  • 0 in reply to Satyaharika Ananthagiri
    TI__Genius 9132 points

    Hi Satyaharika,

    Since the signal you are running is at 200MHz which is approaching -3dB loss.  I think you may be seeing bandwidth limitation and you amplitude is decreasing: 1.8 V x 0.707 (-3dB) =  1.24 V instead of a offset voltage.  To fix this you can try increasing the voltage of the signal to overcome the amplitude loss through the switch.

    If you still see the issue, can you remove the TS3A27518E from the board an short the signal path to see if the clk signal is at the same voltage?

    Thanks

    Saminah