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TS3A5223: Upper voltage tolerance of NC1, NC2, NO1, NO2, COM1 and COM2

Masanori Tachibana
Genius 5350 points
Part Number: TS3A5223
Other Parts Discussed in Thread: TS3A24159

Hello support team,

Our customers is evaluating TS3A5223 now.
In the customer's circuit as shown in the figure, 1.8 V is supplied to Vcc, and the voltage generated from 3.3 V is applied to COM1 at Vcc = 1.8 V.

When SEL1 is 'H', voltage at NO1 is as expected at 1.65V.
When SEL 1 is 'L', voltage at NO1 should be 0 V, but it is around 1.15 V.
It seems that the switch does not turn off and leaks.

In the data sheet, the upper limit voltage of the input terminals NOx and COMx is not limited by Vcc.
However, I think that these input voltages have no tolerance above Vcc.
Is my understanding wrong?

Best regards,
M. Tachibana

  • 0
    TI__Mastermind 45350 points

    Tachibana, 

    You have found a datasheet error in the TS3A5223 device.  Devices it this family to have protection diodes from COM to Vcc. If you are operating Vcc at 1.8 V and supplying the COM pin with 3.3 V we would expect to turn on the protection diode and that would be where you are leaking your current from COM to Vcc. I will order some of these parts so that I may test them to confirm our suspicions and correct the datasheet.

    What are you trying to do in your application with the switch? Maybe we can help you find an alternative device like a voltage level shifter?

    Thank you,
    Adam

  • 0 in reply to Adam Torma
    Genius 5350 points
    Hi Adam-san,

    Thanks for your reply.

    I also thought that it could not input signal that voltage is more than Vcc because input terminals have a positive protection diode.
    But I saw the following thread and thought that this device might have tolerance .
    e2e.ti.com/.../536522

    According to your explanation, the datasheet may be wrong.

    Yes, the customer seems to be used like a level shift.
    I heard that the customer already took countermeasures as circuit and will continue to use this device.

    Best regards,
    M. Tachibana
  • 0 in reply to Masanori Tachibana
    Genius 5350 points
    Hi Adam-san,

    Thanks for your reply.

    I have another question.
    Is the voltage of SEL 1 or SEL 2 safe even if it exceeds Vcc?
    (ex. SEL1=3.3V and Vcc=1.8V)
    I think it might be possible since there is a level shift circuit.
    Is my understanding correct?
    Could you please teach me.

    Best regards,
    M. Tachibana
  • 0 in reply to Masanori Tachibana
    TI__Mastermind 45350 points

    Tachibana-san,

    No, you have come across a datasheet error.  The recommended operating conditions should look similar to the TS3A24159 which states the recommended operating voltage is limited by the supply voltage.  The reason is there will be protection didoes that will begin to conduct if the signal on the pins is greater than the supply voltage.  We are still tying to make this change in the datasheet but it will take some time. 

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Genius 5350 points
    Adam-san,

    Thank you for teaching me.
    Because the positive protection diodes are connected to pins SEL1 and SEL2,
    I understood that these digital input pins should not exceed Vcc.

    Best regards,
    M. Tachibana