How do I compute the power consumption of an audio amplifier?

I intend to use this audio amplifier in my project : PAM8019

It has two analog inputs : left channel and right channel. It has two analog ouputs, which are the amplified inputs.

Let's say I follow the typical application circuit on page 2/12 with VDD = 5 V.

How much current from my 5 V power supply would this IC draw when it is playing a sound on both channels?

My reasoning would be like this : it has an "output power" of 3 W. So at max. gain, I = P / U = 3 / 5 = 0.6 A. That would be the current drawn for each speaker. So finally it draws 1.2 A.

Am I right?

• The total output power will be a lower bound on the input power. With the assumed efficiency of the amplifier, you can turn that into an equality. May 11, 2022 at 12:58
• The datasheet shows an output power of 3W per channel into 4 ohm speakers only when the supply is 5V and the distortion is awful at a horrible 10%. At low distortion the output power is 2W per channel. Do you play a continuous tone at full blast or do you play music or speech that has peaks at 2W but averages 0.4W per channel? Then the total average output power is 0.8W and the minimum efficiency of 80% creates a total output of 1W. The average current is 1W/5V= 200mA plus the quiescent current of 7mA= 207mA total. The power supply must be able to supply bursts of 4W at 5V= 800mA. May 11, 2022 at 16:43

1 Answer

You haven't read the whole data sheet. On page 5, about half way down, it specifies the efficiency, you have to take this into consideration for your calculations as well.
The minimum efficiency at 3W output is specified as 80%. Hence the total power consumption could be 3 X (100/80) X 2 W = 7.5W. And the maximum current from a 5V supply would be 1.5A.
This does not take into account any other inefficiencies of your particular implementation.