I2S DAC with 3W amplifier - MAX98357A

If you’re looking for an easy and affordable way to boost your digital audio files, then the MAX98357 I2S Amp Breakout is for you. It takes standard I2S digital audio input and not only decodes it to analog, but also amplifies it directly to a speaker. Perfect for adding compact amplified sound, it combines 2 breakouts (I2S DAC + Amp) into one.

What is I2S?

I2S is a digital audio protocol used on circuit boards to pass audio data. Many advanced chips and processors handle all audio in digital I2S format. To input or output data, three or four pins are used (data in, data out, bit clock, and left-right channel select). Usually, audio devices use a DAC chip that speaks I2S and converts it to analog that can drive headphones.

This small mono amplifier is surprisingly powerful - it can deliver 3.2 watts of power to a speaker with an impedance of 4 ohms (at 5V supply and 10% THD). Inside the miniature chip is a class D controller, which operates on a supply voltage of 2.7V-5.5VDC. Because the amplifier is class D, it is extremely efficient, making it perfect for portable and battery-powered projects. It has built-in thermal and overcurrent protection, but we barely noticed it getting warm.

The audio input is I2S standard; you can use 3.3V or 5V logic data. The outputs are "Bridge Tied" - meaning they connect directly to the outputs, without connection to ground. The output is a ~300KHz square-wave PWM that is then 'averaged' by the speaker coil - the high frequencies are not heard. All of the above means that you cannot connect the output to another amplifier; it must drive the speakers directly.

There is a Gain pin that can be adjusted to change the amplification. By default, the amplifier gives you 9 dB of gain. By connecting a pull-up or pull-down resistor, or wiring it directly, the Gain pin can be set to 3 dB, 6 dB, 9 dB, 12 dB, or 15 dB.

The ShutDown/Mode pin can be used to put the chip into sleep mode or to set which I2S audio channel is routed to the speaker. By default, the amplifier outputs a (L+R)/2 stereo mix to mono output. By adding a resistor, you can change it to output only left or only right.

Specifications:

• Output power: 3.2W at 4Ω, 10% THD, 1.8W at 8Ω, 10% THD, at 5V supply
• PSRR: 77 dB typ. at 1 kHz
• I2S sample rates from 8 kHz to 96 kHz
• No MCLK required
• Click + Pop reduction
• Five pin-selectable gains: 3 dB, 6 dB, 9 dB, 12 dB, 15 dB
• Thermal shutdown protection
• Comes with 7 header pins and 2 screw terminals