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TXS0202: differences output levels

Sergey Arkhipov
Prodigy 40 points
Part Number: TXS0202

I'm using TXS0202YZPR in the project. The A-voltage is 2.5V and B is 3.3V. When set high level on the D-(A) and D+(A), i see that D-(B) is 3.3V, but D+(B) is about 2.0V. I've tested it on two boards. What is the reason? Schematic:

This is D- 

D+ is:

Best regards.

  • 0
    Guru 266570 points

    There are two D+ pins and two D− pins. Which ones did you measure?

    The schematic is labeled "USB". Is this for USB, or IC-USB?

  • 0
    TI__Guru 57330 points

    Sergey,

    As you have mentioned here in your post, the D+ and D- have differences in voltage levels and the scopeshots shown here in yellow is the B pins, correct?

    What is the difference on the D+(B) pins at the output as compared to the D-(B) pins. Is it measured at the same time or if possible measured one at a time to see if there is any difference in the readings?

    The TXS0202 device supports interchip USB which is different from the regular USB signals. The regular USB signals wouldnt need level translation as i know.

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    On the first measure the blue is D-(A) and yellow is D-(B). On the second blue is D+(A) and yellow D+(B). I use it to translate logic levels between mcu and usb-port.

  • 0 in reply to Sergey Arkhipov
    Guru 266570 points

    What MCU are you using? What connector are you using on the USB port?

  • 0 in reply to ShreyasRao
    Prodigy 40 points

    ShreyasRao said:
    As you have mentioned here in your post, the D+ and D- have differences in voltage levels and the scopeshots shown here in yellow is the B pins, correct?

    Yes, it is.

    The measurements were made at the same time. And this TXS0202 is also used for isolation the board from external voltage. Anyway I would like to understand the reason for this behavior of the chip.

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    Clemens Ladisch said:

    What MCU are you using? What connector are you using on the USB port?

    STM32F407VGT6. The connector is Molex 5015680307.

  • 0 in reply to Sergey Arkhipov
    Guru 266570 points

    The TXB0202 works only with IC-USB (InterChip USB). The STM32F407xx does not support IC-USB. So you cannot use the TXB0202.

    The STM's USB pins already have the correct USB voltages, so you do not need a level shifter.

    You said you want isolation. What kind of isolation? If you want to disconnect the microcontroller from the connector, use analog switches. If you want to protect against overvoltage, use appropriate protection components (e.g., TVS diodes).