for my LORA node I plan to use a STM32L, designated for low power applications.
I figured out that the FLASH memory for my applications (LORA, OLED, BME280, buttons etc.) of 64kb is not sufficient. Therefore, I plan to use the bigger one, STM32L071xy. Since I want to use the same design for backward compatibility with the well-known STM32F103xy PCB breakout board, I tried to use the same footprint as the famous well-known blue PCB.
Unfortunately, I found that LCSC does not offer the STM32L071 in the UFQFPN48 package for JLCPCB but only in the LQFP64 package (STM32L071RBT6). Therefore, I needed to reduce some pins (A11, A12, A15, B3) in order to maintain the well-known pinout.
If you’re trying to preserve a PCB’s external signals from a smaller 48-in chip when using a larger 64-pin one, then only use the pins that exist on the smaller chip.
You might also look at the STM32L073 though, also consider TQFP rather than QFN
And just because your assembly vendor doesn’t have something in their catalog doesn’t mean it’s not ultimately available.
If you’re trying to preserve a PCB’s external signals from a smaller 48-in chip when using a larger 64-pin one, then only use the pins that exist on the smaller chip.
Which pins do you mean in particular? Do you see an additional pin ? VBAT, VDDA?, …
You might also look at the STM32L073 though, also consider TQFP rather than QFN
Indeed, the TQFP would decrease a bit the required space. Unfortunately, my assembly vendor does not offer this.
And just because your assembly vendor doesn’t have something in their catalog doesn’t mean it’s not ultimately available.
I completely agree, but for me it is also a question of cost optimization and cost saving.