Stitching Impedance Analysis of LPDDR Power Plane Split and Its Impact to Radio Frequency Interference (RFI) and Signal Integrity (SI)

This paper presents low-power double data rate 5 (LPDDR5) power plane stitching impedance impact to radio frequency interference (RFI) and Signal Integrity (SI). LPDDR5 power plane split causes RFI and SI degradation, but can be mitigated through appropriate power plane stitching impedance. It is found that stitching capacitor's impedance needs to be less than 10 ohm to minimize RFI and SI degradation. With stitching impedance as low as 0.5 ohm, (a) RFI is suppressed by similar to 20dB, (b) near end and far end crosstalk (NEXT and FEXT) are reduced by similar to 45mV, while (c) eye height (EH) and eye width (EW) improved by 57mV and 31ps respectively. These findings are helpful in improving radio performance of the system and increasing the LPDDR memory speed bin of mobile device.