PAM8304 - Filterless Class D amplifier clicking output

[fantasy2]

Someone explained me that this audioamplifier has a transimpedance opamp configuration meaning it responds to a current rather than a voltage.

I thought the current might be too low for the amplifier to sense anything so I used a headphone output from a phone as input source for the amplifier.. Still no luck.

With this new info, is there a trick I'm missing with these amplifiers?

[Faranight]

Hey!

I know this is an old topic, but it kinda fits the problem I'm having, so I was wondering, if this has been solved yet.
I'm trying to design a small audio player (mono) for a certain application and I've decided to use the PAM8304 class-D amplifier. I ordered like 10 pcs from Mouser and now I'm trying to get one to work. I've soldered it onto a breakout board that I can use in a breadboard, but I've been having this clicking issue as well. Basically I managed to get the audio from a small 8 ohm speaker with some reasonable volume, but that was only working at 3.3VDC supply voltage. When I increased the voltage to above like 3.5V the audio vanished and the speaker started emitting clicking noises (the max allowed supply voltage is 6V according to the datasheet).

So I hooked up the amplifier outputs to my scope to find out what's going on. I noticed that when the supply voltage is at 3V3 I would get a square waveform with some distortions when audio is applied or simply pure square wave when there is silence. But as soon as I increased the supply voltage past 3.5V, the output was... acting weird. It seems as if the chip was going through a shutdown, poweron, shutdown, poweron, shutdown, poweron loop. The square waveform was there, then it disappeared (turned into DC), reappeared for a moment and disappeared again, etc. And each time this happened, a click was emitted through the speaker.

I ended up removing the speaker and connecting a 1 kOhm resistor across the output instead. I also wired both input terminals via 100k resistors and 100nF capacitors to the GND terminal, which did not solve the issue. It did move the anomaly to a higher voltages i.e. I would get the square waveform on the outputs up to like 4.8V, but once I increased it to 5.0V, the weird poweron-shutdown cycle repeated. I had to lower the voltage down below 4.0V to get a stable waveform on the outputs. I even tried connecting one input directly to the other over a 100k resistor with no success. It seems the waveforms were stable at some point, but as soon as the inputs were disturbed (I only touched the insulated hookup wires on the inputs), the circuit started oscillating. No idea what's causing this. Power pins were decoupled via 1uF foil cap and two 100nF ceramic caps right next to the IC. The power leads on the breadboard had two 100uF 25V electrolytic caps.


https://www.diodes.com/assets/Datasheets/PAM8304.pdf

EDIT: In case anyone else is wondering, I solved it.
It turns out it was a decoupling problem. I had initially soldered the PAM8304 over a small breakout board and then used that in a breadboard circuit to perform the tests before deciding to make a PCB. The decoupling caps were also inserted on the breadboard, but apparently that wasn't enough. What I ended up doing is soldering two additional ceramic 1uF X7R 0805 caps directly across the breakout board just above the PAM8304 chip with some wire. One was soldered across the Vdd pin to GND and the other from PVdd pin to GND. I'm still getting some minor ringing on the scope, but at least the darn thing is now functioning properly. I get decent audio while running it at 5VDC without any oscillations.