SN74LVC1T45: Glitch during power up and power down if driving high, output voltage droops to ~1.25V tracking VCC when entering or exiting tristate

Jonathan Pindur

Part Number: SN74LVC1T45
Other Parts Discussed in Thread: SN74LXC1T45,

Tool/software:

During power on, our externally pulled up output (from a receivers supply) drops to 1.25V as the VCC rails come up. It appears the part is functional at 1.25V, below the 1.65V levels mentioned in the datasheet.

Is there some way to use this part without producing a low level pulse? Even with a sharper supply ramp, there will still be an edge generated.

A similar issue is occurring on the power down ramp.

6 months ago

0 Clemens Ladisch 6 months ago

Guru 317750 points

Below 1.65 V, correct operation is not guaranteed. (And this devices does not have an /OE pin.)

Use the SN74LXC1T45, which has glitch-free power supply sequencing (see section 8.3.6 of its datasheet).

0 Jonathan Pindur 6 months ago in reply to Clemens Ladisch

Prodigy 20 points

The current sn74lvc1t45 states the exact same thing about glitch-free supply sequencing. I suspect the SN74LXC1T45 will make things even worse as it will turn on at even lower voltage as its rated for 1.1V compared to 1.65V for the current part (which drives the output to VCC at 1.25).

0 Joshua Salinas 6 months ago in reply to Jonathan Pindur

TI__Mastermind 25290 points

Hello Jonathan,

I would still advise using the part within the recommend conditions. As Clemens stated, anything below 1.65V is not guarantee to work.

Regards,

Josh

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SN74LVC1T45: Glitch during power up and power down if driving high, output voltage droops to ~1.25V tracking VCC when entering or exiting tristate