Hello Team,
My customer used SN74LVC2G04, and they only use one channel 1A/1Y, below are their schematic, pcb and test waveforms.
When 1A has a level transition, we can find there is big noise of VCC. If they set the scope to 20MHz bandwidth, the ripple is about 20mv, and if we set full bandwidth, the noise of Vpp is about 300mV. Customer did some tests below, please help to give your comments. Where does this noise come from? Huawei use 3.3V power supply, although there is big noise, but the voltage is also smaller than 6V, so there should be no risk, correct? Thanks
1. Increase the rise time of 1A, there is no improvement of the noise of Vcc
2. The Vcc test point is more far from our part, the noise is smaller
3. Increase or reduce the filter cap of Vcc, there is no improvement
4. Delete resistor R3970, no improvement
5. Other boards also have the same problem
Regards,
Nanfang
