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TXB0104: Details about specification of the device when either VCC_A or VCC_B is 0V

Nicolas Juteau
Prodigy 20 points
Part Number: TXB0104

Hi everyone,

We would appreciate some clarifications regarding two sections of the datasheet that looks like somewhat contradictory:

1) In section 10 of the datasheet, it is stated that "During operation, ensure that VCC_A <= VCC_B at all times."

2) In table of section 6.5, the supply current of either VCC_A or VCC_B is specified with conditions when either of the supplies are 0V (i.e: disabled), which somewhat contradicts the condition VCC_A <= VCC_B at all times.

Is the condition VCC_A <= VCC_B at all times is solely for the working purpose of the device or not respecting this condition might damage the device?

We are working on a device whose design respect the aforementionned condition VCC_A <= VCC_B. However, while the device is sleeping, it would benefit (current consumption wise) from disabling VCC_B (0V) while keeping VCC_A ON during sleep, hence our question:

Does the TXB0104PWR risks damage if VCC_B is disabled during the device sleep, when no voltage translation is required inbetween?

Regards,

Nicolas Juteau, ing. jr. / Jr. Eng.

  • 0
    Guru 317350 points

    When either supply is at 0 V, the device does not operate. So "during operation" does not apply.

    Section 10 of the datasheet says:

    During power-up sequencing, VCCA ≥ VCCB does not damage the device, so any power supply can be ramped up first.

  • 0 in reply to Clemens Ladisch
    Prodigy 20 points

    Following the above clarification kindly provided by Clemens, and other parts of section 10 in the datasheet:

    The device has circuitry that disables all output ports when either VCC is switched off (VCCA/B = 0 V)

    Provided that the output enable (OE) is correctly managed, it is safe to assume that disabling VCC_B when the device is not in operation does not damage the TXB0104 nor the surrounding circuits.