• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 3 answers
  • Subscribers 17 subscribers
  • Views 204 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

SN74LVC2G66: 1bit bidirectional switch

Takashi Yamaguchi
Genius 11090 points
Part Number: SN74LVC2G66
Other Parts Discussed in Thread: SN74LVC1G66, SN74CB3T1G125, SN74CBTLV1G125

Hi team,

My customer is looking for an 1bit bidirectional automatic switch like I2C buffer. (They don't need a buffer function because it is unlikely to extend and drive again.) 

Could you let me know the recommended bus switch? How about the SN74LVC2G66?

Regards,

Yamaguchi

  • 0
    Guru 243920 points

    The SN74LVC2G66 has two bits.

    Use the search function to find 1-channel SPST switches. The SN74LVC1G66 works well in many applications.

  • +1
    TI__Genius 10974 points

    Hello,

    The SN74LVC1G66 would be a good choice for this application given the requirements. Covers up to 5V for I2C, single switch, and comes in a variety of package options.

    Thanks!

    Bryan

  • 0 in reply to Bryan Marshall
    TI__Genius 11090 points

    Hi team,

    Thank you for the answer. I got the detailed condition from the customer. Can SN74LVC1G66 support following Case.1 and Case.2?

    Case.1

    • Bidirectional open-drain communication between microcontroller A and microcontroller B.
    • There is a case that only microcontroller A is tunred off.
    • The power supply of this analog switch is shared with A, and the switch keeps turning on while A and B are on.
    • When microcontroller A turns off, analog switch off and disconnect the line
    • Place the open drain pull-up on the A side
    • I'm thinking of protecting the A terminal when A is off.

    Is there any problem with the above usage?

    Case.2

    • In addition to the above usage. Sometimes when both A and the switch are off, the B side goes up to 3.3V. (B side may also have a pull-up).

    Is it okay if voltage is applied to the signal terminals when the power is off? Also, I would like to keep the leakage current to the terminals at this time to less than 1uA, how about that?

    Regards,

    Yamaguchi

  • 0 in reply to Takashi Yamaguchi
    Guru 243920 points

    The SN74LVC1G66 datasheet shows that the I/O port voltage must not go above VCC.

    The SN74CB3T1G125 allows voltages at the I/O ports when powered down.

  • 0 in reply to Takashi Yamaguchi
    TI__Genius 10974 points

    Hi Yamaguchi-san,

    Thanks for clarifying these details. The feature you would need is called powered-off protection which allows the inputs to see a voltage when the mux is powered off without the risk of backpowering downstream devices or accidentally turning on the switch. For a 1:1 mux and maximum voltage of 3.3V, the SN74CBTLV1G125 would be the part I would recommend in this instance and would satisfy both scenarios you outlined.

    Thanks!

    Bryan

  • 0 in reply to Bryan Marshall
    TI__Genius 11090 points

    Hi Bryan-san, Clemens-san,

    Thank you for the proposal. From the SN74CBTLV1G125 d/s, it seems that the leak current is 10uA when Vcc=0V, VI or VO = 0 to 3.6 V. Do we have 1uA leakage current device?

    Regards,

    Yamaguchi

  • 0 in reply to Takashi Yamaguchi
    TI__Genius 10974 points

    Hi Yamaguchi-san,

    The lowest leakage part you can use would be the TS5A3167 which has a 0.05uA typical powered off leakage spec (up to 15uA across temperature).

    Thanks!

    Bryan