VIA VT6103 EMI DESIGN RESEARCH

VIA VT6103 EMI DESIGN RESEARCHVIA VT6103 EMI DESIGN RESEARCH

Andree 2002.8.8.

1.Subject

2.Symptom
Symptom: Lan port radiate 200,250,350 IME noise.VA I TV 6103 i w ll a h e v IME noise around 200,250,350 . zHM

3.Analysis

Analysis table
ITEM freq Db 1 200 -6 6 SOULTION Remark put measure at decoupling cap. for VCC TX+ p ut decoup ling cap . for VCC and p ut cap . On 3V_DUAL put decoupling cap. for VCC and put cap. On 3V_DUAL,P UT v cc5 cap. Put cry stal cap. As far as TX+/-,

2

35 1

-6 0

3

200,25 0 ,35 0

-7 0

4.Solution

5.Circuit
102p
3V_LAN C188 3VDUAL 3V_LAN TXTX+ RXRX+ R193 R192 R191 R190 49.9RST 49.9RST 49.9RST 49.9RST C184 103P 32 33 40 41 RXRX+ TXTX+ ACT_LED R166 R183 330 330 3VDUAL 3V_LAN LED0/TEST# LED1/SPD100 LED2/DUPLEX LED3/NWAYEN INT#/PHYAD0 REXT SD/FXEN PD# RST# XI GNDOSC GNDRX GNDTX GNDTXC