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TS5A3157: If no power on V+ (pin5), how many resistance between COM and NO pin?

Part Number: TS5A3157
Other Parts Discussed in Thread: SN74CBT3306

Hello Sir:

Please refer our schematic as below.

If no power on V+ (pin5), how many resistance between COM and NO pin?

And how many resistance between COM and NC pin?

We measured about 26Kohm between COM and NC, or COM and NO.

Is the resistor value correct?

Please help to provide your recommendations for us.

Thanks a lot.

   

  • As shown in the recommended operating conditions table, when the power if off (V+ = 0 V), the only allowed I/O voltage is 0 V. If you try to apply a higher voltage, a current will flow through the ESD protection diodes into V+.

    You should power the switches from a supply that stays on. Alternatively, bus switches like the SN74CBT3306 allow to apply a signal even when the power if off, but work only with a 5 V supply.

  • Hey Statham,

    I'm not sure what the resistance would be, as you're using the device out of the recommended operating range, as Clemens said. The recommendation would be to either power sequence so you aren't applying a voltage to the pins when the device is off or switch to a device that has powered off protection that will allow voltage on the I/O's when the device is turned off. 
    The TS5A63157 may be the easiest replacement here.

    Thanks,
    Rami