SN74HCS125: Max Output to Output Skew for SPI signals

Hi Clemens,

Max SPI frequency will be 25 MHz .

~1ns seems to be on higher side for SPI signals. What are your thoughts on this?

Thanks,

Lalit

Hi Lalit,

Many customers use our buffers for SPI without issue. Most if not all of our devices can operate fine at 25MHz. However given that you are transmitting over cable and concerned about skew it might be better to use a device intended for long distance buffering that specs jitter/skew such as one of our LVDS buffers.

Best,

Malcolm

The actual value will be smaller than 1 ns. But the exact value is not known.

Anyway, at 25 MHz, the length of a pulse is 20 ns, so the buffer's skew is negligible. The largest problem would be the cable, and the delay between MOSI and MISO.

Hi Clemens,

Thanks for your inputs.

Just one more query.

Is there any footprint compatible part which has Schmitt trigger inputs but input is 5v tolerant when VCC=3.3v?

I think SN74HCS125 is not 5v tolerant if VCC=3.3v.

Thanks,

Lalit

Hi Clemens,

The parts you have suggested are not footprint compatible.

Does it mean TI does not offer four channel Schmitt trigger input buffers which doesn't have positive clamp diode?

Thanks,

Lalit

No, there are no such device in the same footprint.