This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • Resolved

TS3A24157: Connection between COM and NO/NC when VCC=0v

Guru 16770 points

Replies: 8

Views: 2215

Part Number: TS3A24157

Hi

Do you have information of the connection status between COM and NO/NC when VCC=0V?

Does it depend on digital control input (VIN1, VIN2)?

We checked the resistance between COM and NC/NO was approximately 5kohm.

Is this normal?

BestRegards

  • Na Na,

    We do not have information of the connection status between COM and NO/NC when VCC=0V.  We do not guarantee the impedance of the TS3A24157 when Vcc= 0 V because it does not have the powered off protection feature. 

    If you would like a device that is in Hi-Z state when Vcc= 0v you need to find a device with Ioff or Ioff protection like the spec below from the TS3USB221.  It shows that there is little leakage through the signal path. 

    Why do you need to have the device Hi-Z when Vcc = 0V in your system?  Would you be able to use the 2 channel 1:2 TS3USB221 device instead of the TS3A24157?  

    Here is another post the also describes this powered off protection feature. 

    Thank you,

    Adam

  • Guru 16770 points

    In reply to Adam Torma:

    Hi Adam

    Thank you for your suggestion.

    TS3USB221 has select input but it seems to control two channels at the same time.
    I need 1:2 two channel switch that can be controlled independently like TS3A24157.

    By the way, TS3A5223 has Ioff and it has Vin_max=4.3V as absolute maximum ratings.
    So, I think TS3A5223 is allowed to apply the voltage at the analog input when VCC=0V. Is my understanding correct?

    If it OK, I would select TS3A5223 instead of TS3A24157.
    (Although the pin-compatible device would be the best...)

    BestRegards
  • In reply to na na78:

    Na Na,

    By the way, TS3A5223 has Ioff and it has Vin_max=4.3V as absolute maximum ratings.
    So, I think TS3A5223 is allowed to apply the voltage at the analog input when VCC=0V. Is my understanding correct?

    No, the TS3A5223 is not allowed to apply the voltage at the analog input when VCC=0V.  Our datasheet naming for these specs is currently not consistent.  If you look at the Ioff spec in the TS3A5223 it shows that the Vcc = 3.6V during the test.  You need to find a spec with Vcc=0V and placing a voltage on the signal path to see if it leaks to the other side of the FET switch.

      

    You need to find a spec like the SN74CB3Q3305 device that shows the leakage when Vcc = 0 V

    Why do you need independent logic control?  The SN74CB3Q3305 switch as independent logic control.  What do think about using this device?

    Thank you,

    Adam

  • Guru 16770 points

    In reply to Adam Torma:

    Hi Adam

    Thank you for your suggestion.

    I'm sorry, my question was insufficient.

    I'm looking for compatible device with TS3A24157RSER (UQFN) allowing to be applied voltage at the analog input when VCC=0V.

    I attach the following image.

    A and B would be the audio signal.

    One channel is fixed (A or B) but another is changed between A and B.

    Let me confirm the following question.

    Unlike TS3A24157, VIN-MAX as absolute max rating of TS3A5223 is independent on Vcc.

    In other words, I thought TS3A5223 dosn't have ESD diode at the analog input and it could accept the analog input (-0.3V to 4.3V) when VCC=0V.  

    Do you have VCC condition when VIN-MAX of TS3A5223 is determined?


    Regarding to your reply, TS3A5223 is not allowed to apply the voltage at the analog input when VCC=0V.  

    So you mean the TS3A5223 would be damaged if the voltage is applied when VCC=0V,  don't you?

    BestRegards

  • In reply to na na78:

    I found a device that could meet requirements but will have some unused channels SN74CB3Q3253

    Are you trying to pass an analog signal through the device that is centered at 0 V.  If this is the case you will need a device with negative voltage swing capability like the TS5A22362 to TS5USBA224? 

     

    You are correct since Vin-max abs max rating is not relative to Vcc there is not a protection diode that will begin to conduct.  However, we cannot guarantee what condition the I/O signal path will be when Vcc = 0V for the TS3A5223 because we do not have it specified in the datasheet.

    According to the datasheet  abs max spec you will not cause permeant damage or risk reliability issues if Vcc = 0V and a voltage up to 4.3V was applied to the I/O signal path.  However, we still can't tell you how much current will leak through the device under this condition.   

     

    It seems like it is tough to find an exact device that meets all of your requirements.  What is the reason you need to know the state of the device when Vcc = 0V?  Is this a flexible requirement? 

     

    Thank you,

    Adam

  • Guru 16770 points

    In reply to Adam Torma:

    Hi Adam

    Thank you for your reply.
    I could have understood applying voltage (up to 4.3V) is allowed but the leak current (or IO impedance) is not defined when VCC=0V in TS3A5223.


    Could you please check if the following understanding is correct?

    Regarding to TS5A23159, it has the capability of isolation in power-down mode when VCC=0V.
    In addition, it offers INC/INO/ICOM(PWROFF) when VCC=0V.

    So, I can obtain the following for 3.3V supply:
    R=3.3V/0.2uA@25℃ = 16.5Mohm


    TS5A23159 can define the state of IO as HI-Z when VCC=0V.
    In other words, TS5A23159 can accept applying voltage at analog IO when VCC=0V.
    Is it correct?
    (I'm confusing because VNC/VNO/VCOM are limited -0.5V to VCC+0.5V as absolute maximum ratings)


    BestRegards
  • In reply to na na78:

    Na Na,

    Now I think I see your confusion with these specs especially when it appears the TS5A23159 absolute maximum ratings table and the electrical specifications table are in conflict.  I agree that this feature is specified in a confusing way in the datasheet.  Our newer switches like the TS3USB3000 I think specify this feature more clearly.

    If you look at the qualifying notes in the abs max ratings you can see that these specifications can be exceeded in certain cases

    Note 1 says that exceeding these values in the table may cause issues but doesn't mean it will always cause issues.

    Note 4 says that you can exceed the stated voltages on the I/O pins as long as you don't exceed -50mA current clamp rating

    Note 5 gives you the absolute maximum voltage of 5.5 V for the I/O pin  

    Yes the TS5A23159, has the capability of isolation in power-down mode when VCC=0V.
    In addition, it offers INC/INO/ICOM(PWROFF) when VCC=0V.

    You can obtain the following for 3.3V signal on the I/O pins when the supply equals Vcc = 0V:
    Resistance on the I/O signal path =3.3V/0.2uA@25℃ = 16.5Mohm


    The TS5A23159 can define the state of IO as HI-Z when VCC=0V. 
    The  TS5A23159 can accept applying voltage at analog IO when VCC=0V.
     

    Thank you for asking these questions since it is confusing even for me since all these devices were designed at different times, with different engineers, and with different ideas on how to specify the part.  I'm sure other people in the e2e community appreciate the questions as they may have the same issues. 

    Adam

     

  • Guru 16770 points

    In reply to Adam Torma:

    Hi Adam

    Thank you for your explanation.
    I could understand the contents clearly.

    BestRegards

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.