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About using comparator to detect tip pin

Tsukui Yusuke
Guru 21930 points

Other Parts Discussed in Thread: TLV7041, TLV7031

Hi,

Customer wants to detect audio jack insertion with the following configuration.

■4pin earphone jack "TIP pin"⇒Comparator IN / Comparator OUT⇒TS3A227E DET TRIGER pin

Customer's available earphonejack is a 4 pin product.
For this reason, there is no switch for detecting jack insertion in the jack itself.

I got the following question from the customer.
・Is there a problem by connecting the earphone jack tip pin directly to the input of the comparator?
・Could you tell me the recommended comparator.
　Device image is below.
　datasheets.maximintegrated.com/.../MAX9060-MAX9064.pdf

I look forward to hearing from you.

Best Regards,
Yusuke/Japan Disty

  • 0
    TI__Mastermind 26870 points

    Yusuke-san

    Thanks for your question. As we are on break for the holiday, we will get back to you as soon as possible during the first week of January.

    Chuck

  • 0 in reply to Chuck Sins
    Guru 21930 points

    Chuck-san,

    Thank you for your reply
    I very much look forward to your reply about this issue.

    Best Regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 26870 points
    Yusuke-san
    Since speed is not very important in this application, I would suggest out TLV7031 or TLV7041. The 7031 has a push pull output and the 7041 has open drain output.
    The tip is one of the earbuds and has low impedance. This can be directly connected to an input of the comparator. This forms a low impedance path to ground when connected properly and making good connection. I would also connect a high impedance pull-up resistor to the same input pin. When the headphone jack is not fully inserted, the comparator input pin will be pulled high by the pull up resistor. The other comparator input can have a resistor divider connected to it. One resistor connected to ground and the other connected to the same as the pull-up resistor. Generally this would just be the supply to the comparator. The resistors can be equal value creating a 1/2 supply reference voltage. When the tip is making proper contact it will pull its input pin low, below 1/2 supply. When not connected it will pull the input high, above 1/2 supply.

    This is one way to accomplish this. It is not necessary to use a device with an integrated reference. This is not a precision application.
    Chuck
  • 0 in reply to Chuck Sins
    Guru 21930 points
    Chuck-san,

    Thank you for you kind support.
    I understood your explanation.

    Let me know one more thing.
    ・Does connecting the TIP pin and the TLV7041 affect the sound signal?
    ・Could you tell me a simple circuit of the circuit configuration you think?

    Best Regards,
    Yusuke/Japan Disty
  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 26870 points

    Yusuke-san

    Connecting the TLV7041 will have no impact to the sound quality since the input to the tlv7041 is very high impedance. the comparator inputs are gates to MOSFET transistors.