How to avoid or reduce noise? - low frequency noise
Dear Victory1981,
Please take a look at the following topic, there are some explanations about capacitive decoupling:
**broken link removed**
If You suffer mostly from the low-frequency noise, the best way to suppress it - using active regulation circuitry. Lets say that Your analog part requires +5V power supply, then take something higher (...8-12V) and use additional linear voltage regulator to reduce it to +5V with good capacitive coupling, this may reduce low-frequency noise by ~30-40dB. However be VERY carefull and check if all ot the mixed signal devices (ADCs/DACs or others even having I2C control from digital part, for example) will not latch up if the power from digital side will arrive before the analog power (since it takes time for voltage regulator to charge all the capacitive load and stabilize). If latching up may happen, then use some digital power supply delaying technics (either disabling power supply itself or switching its output voltage) that will ensure simultaneous powering-up of both analog and digital parts.
Best Regards,
F.S.