I want to build a simple, portable, MP3 decoder + amplifier. I use a PAM8610 amplifier and a generic MP3/bluetooth decoder.
When I power each of them from separate batteries (7.4V) it works nicely. When I power them from the same battery (7.4V) I have A LOT of noise, especially when I turn on the bluetooth.
I put capacitors (3300uF and/or 100nF) on the battery. Won't help.
How can I make these two circuits work together without using separate batteries?
Current consumption (MP3 decoder): 50mA in AUX mode, 70mA in BlueTooth mode, 45 in standby mode.
Current consumption (amplifier): 18mA
(without input signal)
Placing a capacitor on the battery won't help. However, placing a 1000uF capacitor directly onto the power connector on the MP3 decoder helps a lot. The noise is at half now. Unfortunately, I don't know which pins are the plus/minus on the IC so I can connect the capacitor directly/closer to the IC. I tried also a 3300uF but the noise decreased with only 5-10%. Considering the size of the capacitor (100uF vs 3300uF), it might not worth it (for a portable application).
Even more, now (after installing the capacitor in the new position) the coil also helps a little. I will try with a bigger coil.