LSF0204: Waveform distortion When the freq over 1M HZ

The waveforms show that the pull-up resistors are too large (there is not enough current to quickly (dis)charge the parasitic capacitances). If you use smaller pull-up resistors, then the driving devices must be able to sink more current.

When you have pull-up resistors on all lines, you can ususally replace the LSF0204 with the TXS0104E, which has edge accelerators that improve the waveform.

But in the case of SPI, all four lines are unidirectional, so the best choice is a translator with active buffers, such as the SN74AXC4T774/SN74AVC4T774.

Hello,

You can also look at our LSF minute videos. These explain the workings of the LSF device and the pullup resistors. It will help give you insight.

https://training.ti.com/introduction-voltage-level-translation-lsf-family?cu=1134826

Thanks!

-Karan

Hi Alex,

Karan explained this with his previous posts. It looks like you will need smaller pull-ups. The videos he linked will provide you with the knowledge to effectively calculate the pull-up sizes to balance data-rate and power.