App note(PDF) on NUF2441FC EMI and ESD filter chip from ON Semiconductor.
The continued ever-increasing integration of more functions into personal electronic devices such as cell phones has made electronics manufacturers demand more integrated functions to reduce part count and save board space. Cell phone manufacturers have also driven component manufacturers to produce more efficient parts to increase the battery life on cell phones. Quite often though this is done at the cost of added sensitivity to ESD. Concurrently, as data rates and clock speeds increase the need to filter Electromagnetic Interference (EMI) also needs to be resolved. The ON Semiconductor NUF2441FC was designed to provide both ESD protection and EMI filtering for headset and speaker phone lines in cell phones with low line losses. This dual function component reduces part count and significant board space in a Flip-Chip package offer excellent performance at a low cost.