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TMUX1574: TMUX1574RSVR

syed S
Prodigy 110 points
Part Number: TMUX1574

Tool/software:

Hi Team,

I am using TMUX1574RSVR for the SPI MUX in my design, where 2 master SPI will be connected to source side of MUX chip & Drain side will be connected to SPI flash.

while doing DC analysis, there is no VIH, VIL and VOH, VOL values for the Source & drain pins of the TMUX1574RSVR datasheet.

one of the 2 master's is failing in the DC,

1.(Master) SOC which has VOH=2.475, VOL=0.825, when i consider the MUX has only FET with Rdson of 4ohm (max) with 0.1mV drop bypassing the MUX and comparing the source side and drain side connected device directly with 0.1V drop.

also even if i did not consider the MUX voltage drop in DC analysis, the source side Device & Drain side device is failing in DC for low levels. when we use MUX, do we have better VOL, VIL from MUX, so that DC levels will be met?

How to get the VIH, VIL, VOH, VOL values of the TMUX1574RSVR.

  • 0
    Guru 316780 points

    An analog switch indeed behaves like resistor. It does not have switching thresholds because it does not make any difference between low and high voltages.

    Please note that the VOL/VOH values are specified for a certain test current. When connected to a high-impedance input, the voltage drop will be smaller; see [FAQ] What is the output voltage (VOH or VOL) when the output current is X or the supply voltage is Y? When you adjust for the actual leakage current, the DC analysis is likely to succeed.

  • 0 in reply to Clemens Ladisch
    Prodigy 110 points

    Hi Clemen, 

    if that is the case, shall i consider the VOH, VOL values of the driver IC & the VIH, VIL values of the Receiver IC for the Dc analysis. by ignoring FET in-between, the input & output of the MUX, as Im using this MUX for SPI signals.

  • 0 in reply to syed S
    TI__Mastermind 18095 points

    Hello Syed,

    The TMUX1574 is a passive device that doesn't actual drive any signal on it's own. It only passes the I/O signal through, depending on the logic. So there isn't any VIL, VIH, VOL or VOH for these pins. They are just analog I/O's.
    The logic pins control the switching and have VIH/VIL levels that are listed in the datasheet under the electrical characteristics. These will be dependent on the VCC level. 

    In a DC analysis the mux can be considered as a resistor. 

    Thanks,

    Nir