RF switch supply from GPIO pin as output?

AZube.2 · ‎2022-07-07

Can anyone confirm if it is okay to supply the RF switch directly from a general purpose output of the STM32WL? This way I could control when the switch is working or when the antenna is isolated (off) from the circuit.

I see in the datasheet for the STM32WL that "The GPIOs can sink or source up to ±8 mA, and sink or source up to ± 20 mA (with a relaxed VOL/VOH)". While for the RF switch the typical supply current is of 65uA and a maximum of 110uA.

Seems that it should be okay. Could anyone that has done this or anyone with the knowledge confirm this is a good practice?

Thanks and best regards,

Asier

Benoit MARCHAND · ‎2022-07-08

Hello,

Yes, it is perfrectly fine to control RFSwitch through GPIOs.

This is what is done on stm32wl nucleo board (https://www.st.com/en/evaluation-tools/nucleo-wl55jc.html)

You can find an implementation of the control in stm32cubewl (https://www.st.com/en/embedded-software/stm32cubewl.html) in the ATSlave application example.

BR,

Benoit

View solution in original post

Andrew Neil · ‎2022-07-07

Well, ST's own B-L072Z-LRWAN1 board supplies its TCXO from a port pin - so it should be fine to supply just an RF switch...

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Benoit MARCHAND · ‎2022-07-08

Hello,

Yes, it is perfrectly fine to control RFSwitch through GPIOs.

This is what is done on stm32wl nucleo board (https://www.st.com/en/evaluation-tools/nucleo-wl55jc.html)

You can find an implementation of the control in stm32cubewl (https://www.st.com/en/embedded-software/stm32cubewl.html) in the ATSlave application example.

BR,

Benoit