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TXS0104E: Maximum Load capacitance

Takuya Terada
Expert 5425 points
Part Number: TXS0104E
Other Parts Discussed in Thread: TXB0104

Hi team,

my customer used TXB0104 as level shifter for UART.

But oscillation was occurred. Maybe bacause of load capacitance.(70pF is maximum, right?)

So customer needs the level shifter that have higher maximum load capacitance.

I think TXS series could be the option for them, but i cannot find maximum load cap value.

so could you tell me max CL?

best regards,

Takuya

  • 0
    Guru 319220 points

    Both the TXB and the TXS will oscillate if there is ringing on the line. (The ringing will trigger the edge accelerators.) Are there long traces, cables, or connectors?

    Section 4 of the application report A Guide to Voltage Translation With TXS-Type Translators (SCEA044) says:

    There is a tradeoff between achieving a maximum data rate and driving heavy capacitive loads simultaneously. With heavy capacitive loads, the one-shot can time-out before the signal is driven fully to the positive rail. In this scenario, only the pull-up resistors will pull the line high in accordance with its RC time-constant determined by the resistive and capacitive loadings. It is best to avoid this condition by driving capacitive loads less than 70pF when maximum data rate are desired. With capacitive loading >70pF, the TXS-type devices will still successfully operate at lower data rates.

    UARTs are not fast, so the TXS should work.

    But for unidirectional signals like this, it would be a better idea to use a direction-controlled translator. What voltages and how many signals in each direction are required?