Reference circuit for QFN40 package

[Halfdan]

Hi I'm implementing the QFN40 variant of nRF54L15 in our design but I can only find reference circuits for the QFN48 and the CSP47 packages.

Can you provide this for the QFN40 package too?

Alternatively, can you specify the expected impedance on the antenna pin/matching network and current draw on each VDD pin?

Best Regards,

Halfdan

[SwRa]

Hi Halfdan,

The QFN40 variant for nrf54L15 is currently in sampling and hence why it is not available: https://academy.nordicsemi.com/courses/nrf54l-series-express-course/lessons/lesson-1-architecture-overview/topic/nrf54l-series-socs/#Packages  I can check for the reference circuit design and get back to you. 

can you specify the expected impedance on the antenna pin/matching network

It is always recommended to match the SoC + antenna to a 50 Ω reference point. See hjere: https://academy.nordicsemi.com/courses/nrf54l-series-express-course/lessons/lesson-1-architecture-overview/topic/hardware-layout-and-design/ 

Regards,

Swathy

[Halfdan]

Thank you, to match the SoC to 50Ω, I would need to know the expected impedance of the SoC or have documentation with recommended matching. We are sampling this part now, but without this info for the layout I expect our prototypes will have degraded performance.

[SwRa]

Hi Holden,

Since the part is in sampling, you will need to contact your Regional Sales manager for information regarding the reference design. The matching circuit will likely look similar to that of the two other designs available.

As for the impedance, this is what I heard back from the experts:

"The impedance seen into the ANT pin is not interesting. The important impedance is what the ANT pin sees into the matching network. And even this doesn't show the full picture as you need to control the level of the harmonics as well. 
While the PA will change for different output power setting, the matching network in the reference design found in the product specification will provide the best performance across all power settings. Also, it's not straight forward to measure this as the VNA will provide incorrect impedance and offset the PA while measuring.
If you have alternative matching network designs, it's better to measure the impedance seen into the matching network, from the antenna side, with the radio in different power settings and adjust the component values so that you measure close to 50 ohm"

Regards,

Swathy