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TMUX1574: Max channel current

Jay Yeh
Intellectual 465 points
Part Number: TMUX1574
Other Parts Discussed in Thread: SN74CBTLV3257, TS3A44159, TS5A3166,

Hi 

I would need a 2:1 (SPDT) multiplexer to switch the ISO7816 signal for my application.

Basically I would need 3 channels for signal and one channel for power supply.

The max power is around 25mA.

Is it safe to use [S1A S1B] for Vcc power switch and [S2A S2B], [S3A S3B], [S4A S4B] for the communication signal RST, IO and CLK?

Or it is better to choose SN74CBTLV3257 as the channel max current is documented to be 128mA?

Thanks

  • 0
    Guru 268650 points

    The voltage drop over that switch would be 64 mA × 5 Ω = 0.32 V.

    The on-resistance of the switch should be as small as possible. Consider the TS3A44159 if the voltage and frequency match. Otherwise, use a larger device with multiple channels in parallel for the power, or use a better switch like the TS5A3166.

  • 0
    TI__Mastermind 46347 points

    Hi Jay,

    The max current shouldn't be an issue, unless you are operating in high temp environments; the max current is rated for max temp operation, but usually can be higher when the temperature isn't reaching towards max. If you operating in a higher operating temp (<= 125C) then I would suggest switching to the SN74CBTLV3257, just so that abs max current is not violated. 

    As Clemens indicated, you will lose voltage over the signal. If you are pulling 25mA with an Ron of ~2 Ohms, you will lose 50mV over the switch. If the device in which you are passing the current to can handle the 50mV drop in voltage there shouldn't be an issue. 

    What are the power requirements of the device you are feeding through the TMUX1574? 

    Best,

    Parker Dodson