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What accounts for the variation in RFO_LP, RFO_HP output filter values for STM32WL MCUs?

Associate III


I have a question regarding the reference design MB1389-WL55JC-highband-E02_Schematic (

The MCU has two RF outputs, one for high power and another for low power. Both outputs connect to an RF switch through identical filter schematics, but with different component values.


I have a few questions. If these filters are frequency-related, why do the values differ when both ports are supposed to output the same frequency? I simulated both schematics for the 800-900MHz range (attached), and the difference is only 1 dBm.

Could you please advise on why the components in each filter scheme are different?

Additionally, the MCU datasheet's Sub-GHz radio characteristics section states that "All RF impedances matched using reference design." This reference design is for STM32WL5JC MCUs. If I want to use other MCUs like WLE5 or WLE4, do I need to calculate all those filter values separately?

Thanks in advance