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SN74LVC1T45: Power-up sequence

toshi-e2e
Genius 4850 points
Part Number: SN74LVC1T45


Hi Experts,

I have two questions about SN74LVC1T45 power-up sequence.

Q1.
The SN74LVC1T45 PCN adds the following new power-up sequence recommendations: Does the SN74LVC1T45  manufactured before PCN require the same power sequence or does it apply only to products after PCN?
===============================
The recommendation is to first power-up the input
supply rail to help avoid internal floating while the output supply rail ramps up.
can be ramped up simultaneously.
===============================

Q2.
SN74LVC1T45-Q1 is a product with the same function as SN74LVC1T45.
The power sequence of this product is as follows.
I think the two products have the same basic design, but there is a difference in the power sequence. Which power sequence is recommended for SN74LVC1T45?
===============================
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.
TI recommends that the inputs are grounded during power up. Take care to assure that any state changes do not
affect system level operation.
===============================

Thanks in advance

Regards,
Toshi

  • +1
    TI__Intellectual 1450 points

    Hi Toshi,

    Q1. Agnostic of PCN - for the SN74LVC1T45 the datasheet mentions power sequencing recommendations. Please note that the power sequencing can be modified according to the needs of the application/system without any performance or reliability concerns to the device.

    Q2. For SN74LVC1T45 there isn't a supply sequence restriction. The recommendation is to help make sure the control circuitry is supplied first as it should be powered by VCCB. 

    Hope this helps.

    Best,

    Swathi