How to drive the L9823 (SPI) via 3.3V MCU?

[smhhadima]

Posted on March 27, 2017 at 18:51

I'm using STM32F303 which operates on 3.3V 

how can I communicate with the L9823 SPI which runs via 5V?

thank you

[Peter BENSCH]

Unfortunately, the question ended up in the wrong subforum a long time ago, so the answer will no longer help the TO. For the sake of completeness and in case someone stumbles across the same question:

• E-L9823 (and the meanwhile obsolete L9823) require an H level of at least 70% VDD, so 3.5V for the typical VDD of 5V
• STM32 have CMOS outputs and deliver at least Vdd-0.4V at the output under normal load, i.e. 2.9V at Vdd=3.3V

To bring this H level to the value required by the E-L9823, a voltage translator or level shifter is necessary. A simple stage with open-drain or open-collector is not sufficient as a level shifter, as this does not achieve the required transmission frequency due to the passive pull-up.

Regards
/Peter