Pmod AMP3 Reference Manual

The Digilent Pmod AMP3 features an Analog Devices SSM2518 2 Watt Class-D Audio Power Amplifier. The module enables the use of I²S audio protocol or TDM to produce stereo audio at various sampling frequencies. Users may configure the digital volume and dynamic range control via an I²C interface. Additionally, the Pmod AMP3 may be used in a stand-alone mode that does not require the use of the I²C interface.

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  • Audio amplifier with left and right channel separation
  • Stereo output via two standard 1/8“ (0.32 cm) mono speaker jacks
  • Supports common I²S audio formats
  • Digitally configurable volume control for each channel
  • Dynamic range control
  • Stand-alone mode for systems without I²C interface
  • 12-pin Pmod port with I²C interface

Functional Description

The Pmod AMP3 utilizes Analog Devices SSM2518 to reproduce digitally fed audio signals in separate left and right headphone jacks. The separation of the jacks enables better audio signal isolation.

Interfacing with the Pmod

The Pmod AMP3 communicates with the host board via the I²C protocol. Users may operate the Pmod AMP3 in either an I²C programmable mode or a simple stand-alone mode. The stand-alone mode is the default setting and can be activated by removing the shorting block on jumper JP5. When the stand-alone mode is active, jumpers JP3, JP4, and JP6 allow a simple hardware configuration of the amplifier.

Within the stand-alone mode jumper JP3 configuration determines whether to use Standard or Left Justified I²S protocol. Jumper JP4 determines if the MCLK input is 256 or 384 times the audio sampling frequency Fs. The jumper JP6 configures the amplifier to output at either 0dB or +12dB gain.

If JP5 is loaded, I²C is enabled so that the on-board chip can be configured. Consequently, the shorting blocks on both JP3 and JP4 must be removed so that the SCL and SDA lines are pulled to a logic high voltage state. JP6 sets the I²C address of the Pmod; both addresses are valid, but a user may want to use one particular address if another I²C device on the bus is using the other address.

Connector Descriptions
JP5 Unloaded (default Stand-Alone Mode) JP5 Loaded (I²C Programmable Mode)
Loaded Unloaded Loaded Unloaded
JP2 MCLK-provide own external MCLK BCLK-route BCLK to MCLK input Don't Care Don't Care
JP3 I²S (Standard) Left Justified Prohibited Required
JP4 256x Fs 384x Fs Prohibited Required
JP6 12dB Gain 0dB Gain ADDR: 0110100[r/w] ADDR: 0110110[r/w]

Note: Both the 0dB and +12dB gain modes are very loud. You should take care to protect both yourself and your equipment when operating in stand-alone mode. Digilent recommends that you use the programmable mode and set the gain to -12dB or lower.

The I²C programmable mode is used to set alternate Master Clock (MCLK) and Bit Clock (BCLK) ratios as well as configure the Dynamic Range Control (DRC). More information about these options is available in our user guide.

To transfer audio data in the I²S audio format, the MCLK, BCLK, the Left/Right Word Clock (LRCLK), and the data (SDATA) will need to be provided either internally or externally as appropriate. This module is able to receive audio data anywhere between 8 and 32-bits of resolution. An example timing diagram from Texas Instruments on how I²S data is to be sent to the module is provided below:

Example I²S Timing Diagram

Pmod AMP3 Block Diagram (click to enlarge)

Pinout Table/Diagram

Header J1
Pin Signal Description Pin Signal Description
1 LRCLK Left/Right Word Clock 7 NC Not Connected
2 SDATA Serial Data 8 NC Not Connected
3 NC Not Connected 9 MCLK-E Master Clock-External
4 BCLK Bit Clock 10 ~SHUT Shutdown
5 GND Power Supply Ground 11 GND Power Supply Ground
6 VCC Positive Power Supply 12 VCC Positive Power Supply
Header J2 Header J3 Header J4
Pin Description Pin Description Pin Description
1 Left Audio Jack 1 Serial Clock 1 Right Audio Jack
2 Serial Data

Any external power applied to the Pmod AMP3 must be within 2.5V and 5.5V; however, it is recommended that Pmod is operated at 3.3V.

Physical Dimensions

The pins on the pin header are spaced 100 mil apart. The PCB is 1.5 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.

Additional Information

The schematics of the Pmod AMP3 are available here. Additional information about the audio amplifier including communication modes and specific timings of the chip can be found by checking out its datasheet here.

More specific information about how to use the Pmod AMP3 can be found by checking out our user guide. Example code demonstrating how to get information from the Pmod AMP3 can be found here.

If you have any questions or comments about the Pmod AMP3, feel free to post them under the appropriate section (“Add-on Boards”) of the Digilent Forum.