• State TI Thinks Resolved
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 61 views
  • Users 0 members are here
Support feedback
Options
Options
Related

TXB0102: Support Required for TXB0102DCUR Level Translator Issue

Mohammed Arshad M
Prodigy 90 points

Part Number: TXB0102
Other Parts Discussed in Thread: TXU0101

Hi Team,

We are using the TXB0102DCUR IC as a 5 V to 3.3 V level translator. In our design, R286 is populated with a 100 k pull-down resistor, while R288 is DNP.

The measured voltage levels while connecting the HDMI cable are as follows:

Condition Before HPD_1_3V3 Net HPD_1_3V3 Net R288 Connector Side
Without HDMI cable 1.6 V 0 V 0 V
With HDMI cable 1.6 V 0 V 4.2 V

After populating R288 with a 0E resistor, the measured voltages were:

Condition Before HPD_1_3V3 Net HPD_1_3V3 Net R288 IC Side
Without HDMI cable 1.6 V 0 V 0 V
With HDMI cable 1.6 V 0 V 4.2 V

Finally, after lifting pin 5 of the TXB0102DCUR IC, the voltage levels changed as follows:

Condition Before HPD_1_3V3 Net HPD_1_3V3 Net R288 IC Side
Without HDMI cable 0 V 0 V 0 V
With HDMI cable 0 V 0 V 4.2 V

From these observations, it appears that pin 5 of the TXB0102DCUR IC is causing the issue on the HPD_1_3V3 net. Could you please help us identify the root cause and suggest a solution to resolve this issue? The schematics of the following section is attached below.

Regards,
Arshad
image.png

  • 0
    TI__Guru 58511 points

    Hi Mohammed,

    What is the voltage of  VBUS? What is the expectation for the operation of the device and is there waveforms that show expected vs. the anomaly? 

    Regards,

    Jack

  • 0 in reply to Jack Guan
    Prodigy 90 points

    Hi Jack,

    In this device, we are validating the HDMI interface. We are using a TXB0102DCUR level translator to convert VBUS (5V) to 3.3V before connecting it to a 4:8 MUX. The issue we are facing is that the level translator fails to provide the 3.3V output when the HDMI cable is connected.

    Regards,
    Arshad

  • 0 in reply to Mohammed Arshad M
    TI__Guru 58511 points

    Hi Mohammed,

    Are there any waveforms that you can provide for further debug? 

    Regards,

    Jack

  • 0
    Guru 325160 points

    Section 7.3.2 of the TXB0102 datasheet says:

    For proper operation, the device driving the data I/Os of the TXB0102 must have drive strength of at least ±2 mA.

    The 10 kΩ resistors are too weak.

    Section 7.3.5 says:

    The output drivers of the TXB0102 have low DC drive strength. If pullup or pulldown resistors are connected externally to the data I/Os, their values must be kept higher than 50 kΩ to assure that they do not contend with the output drivers of the TXB0102.

    That 1.6 V shows that there is a pull-up/-down resistor that is too strong.

    The TXB0102 is not suitable for handling the HPD signal. Use a unidirectional translator like the TXU0101, which has a high-impedance input that works correctly with any pull-up/-down resistors, and a strong output that can drive any pull-up/-down resistors.