nRF52840 SOM hardware review

[Ping]

Hi There,

    This is Particle's Sr. Hardware Engineer, Ping. We are working on a SoM (System-on-a-module) called EG91-SoM that with a nRF52840 (Thread) + EG91 module for acting as a LTE/2G/GNSS Border Router for Thread.

Attached the schematic and PCB layout (Eagle PCB format) for your review. Thanks!

Best Regards

Ping

[Kaja]

Hi Ping,

here is the feedback:
1. C14 must be 100 nF
2. The matching network for the radio has the values: C5 = 0.8 pF, L1= 4.7 nH and C6= 0.5 pF, these values must be tuned for the specific design.
2. What is the load capacitance, CL, of the crystals you are using?
3. What antenna are you using? 

I will give you more feedback on the layout when I know what antenna you are using.

Best regards,
Kaja

[Ping]

Hi Kaja

    Thank you for your support.

2.  The load capacitance is 12pF +10pF, muRata 10pF(100) ±2% 50V GJM1555C1H100GB01D and  12pF(120) ±2% 50V GJM1555C1H120GB01D

3.  We use the IPEX RF connector to connect the external antenna,The antenna can be customized according to the product structure. we can use Soft plate PCB antenna , such as Taoglas  FXP74 2.4GHz  http://www.taoglas.cn/zh/product/black-diamond-fxp74-2-4ghz-flex-pcb-antenna/  or Taoglas GW.17 2.4GHz Terminal Antenna http://www.taoglas.cn/product/gw-17-2-4ghz-terminal-antenna-ipex-mhf/ 

Best reagards

Ping 

[Andreas]

Hi,

 

I am just bringing you an answer in Kajas absence.

 

2. There should be should be similar capacitance on both pins, for a CL=8 pF crystal this should be approximately 12 pF.

3. This is fine, these antennas should not need any matching, as you have C57, C54 and C2 you should be covered if the via or somethinc causes mismatch.

 

Overall the layout looks very good. There is good grounding and you have replicated our recommendations through the reference layout.

 

Best regards,

Andreas

[Ping]

Hi Andreas，

    Get it，thanks for your suggestion and review.

 Best regards

Ping