3W I2S Amplifier - MAX98357A - Class D

A 3W mono amplifier that work great with the Raspberry Pi

A good news for you Raspberry-Pi! Here is a "all in one" digital audio amplifier board that works perfectly with Raspberry Pi! This MAX08357 I2S Amp breakout board offers low cost digital sound solution easy to setup. It takes the standard I2S digital audio input --> decodes it into analog --> amplify it directly into a speaker. It is perfect to add compact amplified sound since it combines 2 breakouts (I2S DAC + Amplifier) in a single board.

Do not confuse I2S with I2C. I2S is a digital protocol used for sound. I2S is used on boards for audio transmission between circuits. Many advanced chips and processors manage audio stuff at I2S format. Only 3 or 4 pins are nécessary to input/ouput audio data. Pins are data in, data out, bit clock and selection of the right/left channel. Usually, audio devices have a DAC chip that takes I2S as input and convert it to analog (to drive amplifier or headphone).

The small mono amplifier used on this breakout is amazingly powerful! The amp can deliver up to 3.2 Watts into a 4 ohm speaker (10% THD @ 5 volts). The amplifier contains a Class D amplifier powered with a voltage from 2.7V to 5.5V DC. Class D amplifier are very efficient, so there is few power lost in the chip, making it suitable for battery powered projects.
The chip bring a thermal and over-current protection. However, keep in mind that the chip can become quite hot in normale usage and hot enough to burn your finger before the thermal shutdown get activated.

The standard I2S audio input can be used with 3.3V or 5V logic data. The outputs are "Bridge Tied" (not connection to ground), the amplifier outputs are connected directly to the beakout output. The output is a ~300KHz square wave PWM that is "averaged" by the speaker coil - so the high frequencies are not heard. As the output are Bridged this implies that you cannot connect the breakout outputs to another amplifier (it can only drive the coil of a speaker).

The Gain pin can be manipulated to modify the amplifier gain. By default, the amplifier is configured with a gain of 9dB. By connecting a pullup or pull down resistor, or wiring directly, the Gain pin can be set up to 3dB, 6dB, 9dB, 12dB or 15dB.

The ShutDown/Mode pin allows you to place the breakout in shutdown or to set up audio mode for audio channels sent to the speaker. By default, the amplifier will mix the stereo inputs to a mono output (L+R)/2 . By adding a resistor, you can change it to be just left or just right output

This breakout works great with Raspberry Pi, Arduino Zero and any other microcontroller / nano computer with I2S audio outputs

Specification

• Output Power: 3.2W at 4Ω, 10% THD, 1.8W at 8Ω, 10% THD, with 5V supply
• PSRR: 77 dB typ @ 1KHz
• I2S sample rates from 8kHz to 96kHz
• No MCLK required
• Click + Pop reduction
• Five pin-selectable gains: 3dB, 6dB, 9dB, 12dB, 15dB
• Excellent click-and-pop suppression
• Thermal shutdown protection

Content

For each order, you will receive the breakout board assembled and tested. The board is shipped with some connectors (a pinHeader section and 3.5mm screw connector) that can be solder on the board.