• TI Thinks Resolved

TS3A227E: Schematic review

Guru 11715 points

Replies: 6

Views: 113

Part Number: TS3A227E

Hi Sirs,

Sorry to bother you.

Could you help review our schematic as below?

TS3A227E Schematic.pdf

And we have three questions on TS3A227E

1. Is the ground connection of the filter capacitor of Power Pin4 of TS3A227ERVAR connected to Digital GND or Analog GND?

Because we saw datasheet had two type.

2. TS3A227E  DET_TRIGGER# Pin15, is there an internal pull-up resistor to VDD? The other word is I just need to connect Combo Jack's Detect signal HPOUT-JD (connected to GUD_AUD when Headset plug in, like below) to this Pin?

3. Combo Jack's Detect signal HPOUT-JD, the conventional design is connected to the CODE A pin of the Audio Codec ALC262 to inform the Codec HP insertion, but because of the addition of TS3A227ERVAR, it is connected to its DET_TRIGGER# Pin, DET_TRIGGER# has an internal pull-up to VDD. I wonder if this pull-up has an effect on Codec's Sense A resistance judgment. If so, how do you suggest design? Is there a relevant successful design case for reference?

  • Hi Shu-Cheng,

    Thank you for reaching out to us. First the answers to your questions:

    1. This depends on your design if you want to isolate the analog ground from the digital ground to reduce noise in the analog devices.
    2. Yes, the DET_Trigger pin is pulled to VDD. If it is connected to ground by the headphone jack, it triggers a detection.
    3. If I understood th ALC262 correct any high ("1") signal means, that a device has been detected. You'll need to invert the signal at one of the devices and adapt the schematics.
      Check out our inverters here: http://www.ti.com/logic-circuit/buffer-driver/inverting-buffer-driver/products.html#p1299=1;1

    Feedback to your schematic, I've checked your design around the TS3A227E:

    • I don't see a pull-up on SMB_DAT0 to VDD, make sure it is present.
    • We recommend a 10k Resistor on MCP and GND_Sense, as you are connecting it to the codec, your situation will be different.

    Does this answer your questions?

    Best regards,

    Ambroise

  • In reply to Ambroise Suter:

    Hi Sirs,

    Thanks for your reply.

    I am still a little confused about how to design AGND &GND for TS3A227ERVAR.

    1. In this case, the Switch is between the Codec and the Combo Jack.  For the output signal GND_SENSE and input signal G of JACK, both of them should be connected to AGND as codec designed, but, TS3A227ERVAR will connect them to GND via internal GNDFET. (marked as below).

     

    2. If I design the TS3A227ERVAR to only reference to AGND plane, no GND.  Will it bring a big noise to the AGND plane ?  

     

    3.As asked before, do you have a successful design for the Switch which is used between Audio Codec and Combo Jack ?

     

    BTW, the I2C is not used in our design.

  • In reply to Shu-Cheng LIN:

    Hi,

    You're welcome.

    1. See below, as you wont use a FM network, you need to connect GNDA to GND.
    2. The GNDA was designed to support FM Network (chapter 10.2 in datasheet). If FM transmission is not being supported by the application GNDA must be shorted to GND
    3. The only available design we have is http://www.ti.com/tool/TIDA-00565. Unfortunately we don't have an ALC262 design.

    Hope this clarified your questions,

    Ambroise

  • In reply to Ambroise Suter:

    Hi Sirs,
    Thanks for your reply.

    Actually we would like to check if have any risk if we connect output signal GND_SENSE and input signal G of JACK and GNDA and GND to analog GND?

    Because if don't use this switch, that will suggest connect them to analog ground, not digital ground. but 227E suggest connect to digital ground.

    Question: In the figure below, our design requirement is that the G of Audio Jack on the right side of the block diagram is connected to Analog Ground via GND_SENSE on the left side of the block diagram, but this chip has an internal MOSFET that is also connected to the chip's Digital Ground (ie, GND pin) ).
    1. According to our design requirements, the direct connection of the chip to the digital ground should have some impact, but I do n’t know how much the impact is. I do n’t know what the manufacturer suggested?
    2. If 1 has a greater impact, I wonder if the manufacturer recommends that all Digital Ground Pins (GND pins) of the chip be designed as Analog Ground?

  • In reply to Shu-Cheng LIN:

    Hi Sirs,

    Sorry for pushed, have any update on it?

    Thanks!!

  • In reply to Shu-Cheng LIN:

    Hi, 

    thank you for taking your time to post your questions here. 

    You can connect GND_Sense and G (Jack) to GND if you don't need this feature. We recommend to use system GND if no FM is used.

    You should only use Analog GND if you use an FM transmitter in your design.
    The impact depends on your noise on the GND plane, in most cases, this shouldn't be an issue.

    Best regards,

    Ambroise