Hi,
I use the TPA6011A4 to drive dual 4 ohm speaker.
I understand the DC bias voltage on amplifier bridge output should be same. (Balance)
So no DC current flow through the speaker coil and cause heat.
But my issue is:
The Amplifier Speaker - signal (Pin 12) DC bias is 4.1V
Amplifier Speaker + signal (Pin 14) DC bias is 0.9V
So this DC bias unbalance and cause speaker heat!!
Because this speaker amplifier is a daughter board design (See attached AMP.pdf)
1273.AMP.pdf
and install on one current production MB (See attached MB.PNG).
I find the amplifier input signal (into TPA6011A4 pin 5/9) pull down 22K resistor
(On MB R32 and R33) could cause this problem.
When I remove both, this issue had gone away, Amplifier output DC bias balance.
Speaker work fine.
So my question is why this issue happens
I guess below:
1. Because all Amplifier/OP input signals contain DC bias.
In general, that is 1/2 VDD. If VDD=5V, 2.5V DC bias should be on input pin.
So there is 113uA current flow through this 22K pull down resistor from amplifier
input pin.
Maybe this current too high.
But I did not see this current rating in datasheet.
Please comment, thanks.
Harry Wang
