Investigation of noise coupling in mixed-signal system-in-packages (SiPs)

Noise coupling in mixed-signal system-in-packages (SiPs) has been investigated experimentally. Four BGA types of mixed-signal SiPs consisting of a sound source LSI chip (victim) and a speaker amplifier LSI chip (aggressor) have been designed and fabricated for investigating noise coupling from a Class-D amplifier and a DC-DC converter of the speaker LSI to a PLL of the sound source LSI. The two types of the SiPs stack the sound source LSI on the speaker LSI, while the other two stack the speaker LSI on the sound source LSI The measurements of signal-to-noise ratio (SNR) for the PLL signals have demonstrated that a mixed-signal SiP stacking the noise aggressor chip on the noise victim chip is a better package configuration for avoiding noise coupling.