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TMDS361B: Absolute Maximum Ratings of S1/SCL, S2/SDA pin

Kawai
Guru 19785 points

Part Number: TMDS361B

Hi Team,

Please allow me to double check the absolute maximum ratings (AMR) for Pin #32 and #33 which are S1/SCL and S2/SDA respectively.

Our customer is facing I2C issue constantly in the market, asking us that the description is correct or not.

TMDS361B datasheet describes AMR is 5.5V, however, the internal circuit shows the pins have ESD protection diode.

Q1). Is the AMR value described in the datasheet, which is -0.3V to "5.5V", correct for these local I2Cpins ?

Q2). Can user apply signal or pull-up voltage to these pins at VCC=0V without device damage ?

Best Regards,

Kawai

  • 0
    TI__Guru**** 162016 points
    Q1: spec should be correct, AMR means max voltage device can tolerant.
    Q2: it may draw current when Vcc=0v, but should not damage device.
  • 0 in reply to Brian Zhou
    Guru 19785 points

    Hi Brian-san,

    Thanks for your support.

    I understood that the Absolute Maximum Ratings described in the data sheet.

    Please allow me to clarify if there is ESD protection diode at Pin #32 and #33, when used in I2C_SEL pin = Low (device configured by I2C).

  • 0 in reply to Kawai
    Guru 19785 points
    Hi Brian-san and Team,

    Do you have any update ?

    If I2C_SEL pin setting switches the internal circuit, I could understand that there is no ESD protection diode when I2C function is enabled, #32/33 pin used as SCA/SDA.

    If there is an ESD protection diode close to the pin, I think there is always a leakage path through this diode.

    If this is the case, do you mean that this path may draw current, however, device would not get damaged ?

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru**** 162016 points
    ESD protection always there either in I2C function or not. since it's not fail-safe, it may draw current when VCC =0.
    when more question? why you set Vcc=0? you can set device in low power mode.
  • 0 in reply to Brian Zhou
    Guru 19785 points
    Hi Brian-san,

    Thanks for the information.

    The reason is that becuase there could be a case when HDMI siganl is connected before the system power up or just TMDS361B power up due to power sequence. Customer must clarify that the device or I2C function will not get damaged with these use case.

    Customer is facing I2C communication issue. They are investigating the root cause.

    Below are the questions what they have.

    Q3). Can you commit that the device will not be damaged with these situation ? Customer is using under absolute maximum ratings described in the data sheet.

    Q4). Can the ESD protection diode handle this continuous current of 3.3mA ?
    If the I2C pull up supply and the TMDS361B VCC supply are independent, there could be a case when TMDS361B VCC=0V and I2C pull up is 3.3V. I2C should be pulled up with normally a few kohm resistor, which may limit current to 3.3mA@1kohm. From your answer and the AMR specification, we believe this would not damage the device.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    Guru 19785 points

    Hi Brian-san,

    I've checked the leak current when S2/SDA is applied without VCC power supply (VCC=0V).

    From this result, it seems there is only zenor diode between S2/SDA and GND. No ESD protection diode between S2/SDA and VCC.

    This should be the correct design for the I2C pins, because if there is ESD protection diode from S2/SDA to VCC, I2C bus woud be always pulled down when the device is not powered up.

    The data sheet might have the wrong equivalent schematic or it is only applied when used in GPIO mode.

    Thanks for your support. I'm closeing this topic.

    Best Regards,

    Kawai