Schematic review for mm8108-mf15457 HALOW

Hardware
1

Hello Morse Micro team,

PART NUMBER-MM8108-MF15457

GATEWAY SOM-USB HUB.pdf (270.9 KB)

GATEWAY SOM-HALOW.pdf (122.3 KB)

PART NUMBER-USB2514B-AEZC-TR

I am using the MM8108-MF15457 halow module in my new board design. The device is interfaced through USB 2.0 . I have attached the halow schematic and would appreciate it if you could review the design and let me know if there are any issues or recommended improvements before PCB fabrication.

Thank you for your support.

2

Hi @akhil

Some resources that are helpful:
MM8108-MF15457 Data Sheet
MM8108-MF15457 Design Guide
RD09 Reference Design Package

I gave this a quick look. Here’s a couple of things I spotted.

  • You have a distribution switch (U13) connecting your +3V3LCD net directly to 5V. I can’t see any power supply circuit so this would be a major issue to resolve.
  • You will want to attach a ground reference to these LEDs
    image
    image223×250 6.55 KB
  • Our USB reference schematics, and RD09, don’t connect the wake line. Your schematic differs in this regard in that it ties it high. If you are happy with the device not entering Wi-Fi powersave, I don’t think this will cause any issues - just noting it as a difference. Perhaps consider placing a 0R resistor here in case you need to change it later (prevent yourself a board spin).
    image
    image334×315 5.79 KB

When you add regulator from 5V to 3V3, for the best RF performance make sure the supply produces an output peak-to-peak ripple below 30mV. Also consider adding provisions for shielding the power supply circuit to minimise desense.

3

Hi @ajudge

GATEWAY SOM-POWER.pdf (145.6 KB)
Is this power section schematic sufficient for the HaLow module, or should I use a dedicated voltage regulator and power supply for the HaLow section?

Thanks for pointing out the mistakes. I’ll correct them.

4

Without being able to test the supply, it looks ok :slight_smile:

If there are any other “noisy” parts on the +3V3LCD rail you’ll want to consider separating the power supplies, particularly for VDD_TX on the MM8108 module.
Mainly, just make sure your ripple voltage is within the guidelines laid out in the MM8108-MF15457 design guide.