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

smhhadima · ‎2017-03-27

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 · ‎2025-02-12

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

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

View solution in original post

Peter BENSCH · ‎2025-02-12

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

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.