2023-12-19 08:18 AM
Hi everyone,
I am currently in the process of developing a board that incorporates an STM32H743VIT and a voltage level shifter (FXMA108BQX) positioned adjacent to it. The objectives are to translate 3.3V logic levels to custom voltage levels (programmable) when using SPI, and to achieve at least 20MHz on this bus.
Simplified architecture: STM32H743 <-> TMUX1574 (Multiplexer) <-> FXMA108BQX <-> Connector
Problem: I am observing significant overshoots (up to 30%) on the SPI signals when probing at the connector (refer to the attached picture).
Observations:
Questions:
Thank you for your insights and assistance.
EJ
2023-12-19 08:59 AM
Pretty sure the FXMA108BQX isn't looking to follow the slew rate of the STM32, likely has Schmitt triggers with clear thresholds, and then slews with the assumption of a 80-100 MHz signalling, caring little that your application is only 4 MHz
2023-12-19 09:33 AM
Hi @2sayle
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Regards,
Billy