SN74AVC1T45: We observed a glitch on port A when VCCB is in start up

Paulin Xi

Part Number: SN74AVC1T45
Other Parts Discussed in Thread: SN74AXC1T45

Hi TI teams,

For SN74AVC1T45, I deployed below design and there is a pull down resistor on port B. In the design, VCCA will be powered up first, and we observe a glitch on port A when VCCB is in soft-start. Could you help this? and could you clarify the reason?

over 2 years ago

+1 Dylan Hubbard over 2 years ago

TI__Mastermind 42640 points

Hi Paulin,

With the direction controlled architecture of this device, there is potential for glitches during power. This is due to some internal race conditions that result in High pulses when the channel direction is realized. I recommend using the SN74AXC1T45 device instead. This is a newer p2p alternative that has a robust power sequencing that eliminates any glitching. You will also get better power efficiency.

0 Paulin Xi over 2 years ago in reply to Dylan Hubbard

Prodigy 10 points

Thank Dylan. But could you clarify the root of this glitch? what is the internal race condition? and SN74AXC1T45 has no glitch?

+1 Emrys Maier over 2 years ago in reply to Paulin Xi

TI__Guru* 96591 points

Hi Paulin,

Since Dylan probably won't be available again until Monday I thought I'd jump in here to help.

Paulin Xi said:
clarify the root of this glitch? what is the internal race condition?

It's just a result of the design for this device. The internal design of our parts is proprietary - we can't share the details of the design.

Paulin Xi said:
and SN74AXC1T45 has no glitch?

The AXC family was designed recently as a direct replacement for AVC that eliminate glitches like the one you are seeing here. There's an application report that discusses this in detail here:

Glitch Free Power Sequencing With AXC Level Translators

0 Paulin Xi over 2 years ago

Prodigy 10 points

Get it.

Thanks a lot, Dylan, Emrys.

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SN74AVC1T45: We observed a glitch on port A when VCCB is in start up