TPA2017D2: Output current increases at the same input signal level

Hi Roy,

That's right, if the input signal level is increased, so the output level should increase too. As the AGC is disabled, then the output signal won't be limited.
I noticed some details. They are just using one input channel and an output channel, so they could use another mono audio amplifier in their application and the AGC pins are connected to Vdd, so Are you sure that they are not using the AGC?

Best Regards
José Luis Figueroa
Audio Applications Engineer

Hi Jose,

The problem we would like to figure out here, is the output signal level increased while the input signal level DID NOT increase.

Have you seen the situation in other cases? Please suggest what test/modification we could do to fix the problem.

Thank you.

Hi,

The schematic shows that the AGC1 and AGC2 pins are connected and this activates AGC, limiter, compression, and noise gate functions. Then, this explains the device's behavior. These pins should be tied to ground in order to deactivate the AGC.

Best Regards
José Luis Figueroa
Audio Applications Engineer

Hi Jose,

We reworked the board and tied AGC1 and AGC2 to ground. However, we still observed the same phenomenon shown in the waveform below.

(CH2 = Input signal, CH4 = Output Voltage)

Now, this issue happens randomly (about 4 of 20 as of now). The trickiest part is that, on the normal boards, the output voltage remains the same even when AGC is ENABLED.

While on the abnormal board, the same issue would occur even if the AGC is disabled (as the above waveform shows).

Another thing is that, the Vcc of TPA2017D2 is only turned on when there's audio input (a couple of ms ahead of the input signal).

Do you think this could be a quality issue? 

Thanks!

Roy Hsu