ME910C1 mPCIe HW Design Guide
1VV0301642 Rev. 2
Page 20 of 56
2022-01-14
Not Subject to NDA
•
Any PCB power traces to the ME910X1-mPCIE and the Bypass capacitors must be
wide enough to ensure no significant voltage drops occurs. This is for the same
reason as previous point. Try to keep this trace as short as possible.
•
To reduce the EMI due to switching, it is important to keep the mesh involved very
small; therefore the input capacitor, the output diode (if not embodied in the IC)
and the regulator must form a very small loop. This is done in order to reduce the
radiated field (noise) at the switching frequency (100-500 kHz usually).
•
A ground island around Switching regulator components on top layer but well
connected to the common system ground plane in inner layer can help to reduce
noise distribution and consequent spurious generation.
•
The placement of the power supply on the board should be done in such a way as
to guarantee that the high current return paths in the ground plane are not
overlapped to any noise sensitive circuitry as the microphone amplifier/buffer or
earphone amplifier.
•
The power supply input cables should be kept separate from noise sensitive lines
such as microphone/earphone cables.
•
The insertion of an EMI filter on 3V3_AUX pins is suggested in those designs where
antenna is placed close to battery or supply lines.
A ferrite bead like Murata BLM18EG101TN1 or Taiyo Yuden P/N FBMH1608HM101
can be used for this purpose, they are good low band pass filter with frequency cut
about 100MHz.
The below figure shows the recommended circuit:
Figure 3: Power supply EMI filtering recommended circuit
