I'm trying to calculate the current that will be drawn by a 4ohm 3W speaker from a MAX98357a IC amplifier. From my understanding, the amplifier takes in a I2S audio signal (which originates from an ESP32), converts this digital signal to analog then passed through an amplifier with a programmable gain that will be outputted directly to the speaker.
From this I don't fully understand how I can calculate the expected current that will be drawn by the speaker. It is important since this circuit will be powered from a 2500mAh 5V lipo battery and needs to run for a reasonable amount of time.
By searching through the internet, I can see that power output is the important factor in this calculation. Looking at the amplifier IC datasheet, I can see that the output signal level can be calculated by the below equation.
Output signal level (dBV) = input signal level (dBFS) + 2.1dB + selected amplifier gain (dB)
From another stack exchange question, assuming the input signal uses the maximum range, it will result in 0dbFS and choosing a gain of 12dB, the output will result in 14.1dBV. With this number and using the decibel voltage equation 20log10(V/Vo) or 20log10(V) = dbV, the output voltage that will be seen from the speaker is 5.06V.
Using that number and I=V/R I can calculate that the expected current draw will be around 1.26A but that seems to simple and ignores a lot of other things. Overall this all confuses me and don't have any clear ideas on how to tackle this problem.
Any explanation on the principles of how this circuit will play out is best or just any guidance to any other material I can read on.
P.S. This is my very first post on Stack Exchange so sorry for any mistakes in advance.