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SN74LVC1T45-Q1: Power Sequencing in T45 Family

Joseph Bolling
Prodigy 20 points
Part Number: SN74LVC1T45-Q1
Other Parts Discussed in Thread: SN74LVC2T45-Q1

I see the following in the SN74LVC1T45-Q1 datasheet:

A proper power-up sequence is advisable as listed in the following:

1. Connect ground before any supply voltage is applied.

2. Power up VCCB.

3. VCCA can be ramped up along with VCCB.

This is at odds with the sequencing for other T45-series parts, such as the SN74LVC2T45-Q1, which recommends that VCCA be powered up simultaneous with or before VCCB. I want to verify that the datasheets are both correct, and that the power sequencing recommendations for the two parts are in fact different. Thanks!

  • 0
    TI__Guru 59160 points
    Hi Joseph,

    There are no requirements for power sequencing with adverse effects to the device. They are recommendations which may or may not be adhered to depending on the system performance.

    Ramping both of the supplies may sometimes not be feasible, so having ports with the side powered up held at ground is advised. My advise is to also have the control inputs and both the IO ports at gnd during the power sequencing through weak pulldowns.