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TXB0104-Q1: SPI Baud Rate of TXB0104-Q1

Part Number: TXB0104-Q1
Other Parts Discussed in Thread: SN74AXC4T774-Q1, TXU0304-Q1

I applied the 4-Bit Bidirectional Voltage-Level Translator TXB0104-Q1 to the SPI communication port, but there was an issue with the SPI speed.
Data rate is marked as 55Mbps when VCCA=1.8V, VCCB=3.3V on the data sheet.
It should be at least 10 Mbps, but it is difficult to operate over 1 Mbps.
please check.

  • The schematic is incomplete; it does not show what is connected to the I/Os. I suspect that there is some load (long traces, connectors, cables, or pull-up/-down resistors) that violates the limits specified in sections 8.3.3/8.3.5 of the datasheet.

    The correct device for this application would be the TXU0304-Q1 or SN74AXC4T774-Q1.

  • The 1.8V I/O and 3.3V I/O are directly connected to the application processor and microprocessor.
    There is no pull-up/pull-down resistor connected to the signal line.
    By any chance, is it a problem if the output or input port on the GPIO port is set to internal pull-up or pull-down?
    And the currently applied product is TXB0104QRUTRQ1 of UQFN type, and the replacement we found is LSF0204RUTR.
    Is there any problem if I apply LSF0204RUTR to SPI communication?

  • It does not matter if the resistors are external or internal.

    The LSF needs pull-up resistors, and quite strong ones for higher speeds.

  • Hey Kijung,

    Could you share the I/O waveforms that you are seeing issues with? 

    By any chance, is it a problem if the output or input port on the GPIO port is set to internal pull-up or pull-down?

    If you are referring to your MCU's internal pu/pd resistors, they may become a problem if they are too strong. Please see this app note for more information regarding sizing external resistors. 

    Is there any problem if I apply LSF0204RUTR to SPI communication?

    This device can be used for SPI communication, but there are better options. The TXU0304 (also has the UQFN package) for example is a fixed direction translator designed for SPI communications as the I/O is set in specific way that resembles SPI. 

    Regards,

    Jack