PmodAMP2™
Reference Manual
Revision: August 2, 2012
Note: This document applies to REV B of the board.
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Overview
The PmodAMP2 amplifies low power audio
signals to drive a monophonic output. The
module features a digital gain select that
allows output at 6 dB and 12 dB with pop-and-
click suppression. A Digilent 6-pin connector
provides the audio input to the module and a
1/8-inch mono jack supplies the speaker
output.
For customer convenience, Digilent has an
inexpensive speaker and enclosure available
for sale that is suitable for use with the
PmodAMP2. Also, unlike most Digilent Pmod
modules that accept only digital inputs, the
PmodAMP2 accepts analog inputs and pulse
width modulated digital inputs.
Features Include:
•
Analog Devices SSM2377: Filterless,
High Efficiency, Mono 2.5 Watt Class-D
Audio Amplifier
Digital gain select
Pop –and-click suppression
Micropower shutdown mode
1/8-inch mono speaker jack
A 6-pin header for input
2.5V – 5V operating voltage
Figure 1
Inputs and Outputs (I/O)
The PmodAMP2 accepts either digital or
analog inputs at a voltage range of 0-Vcc.
Typically a Digilent system board supplies
power to the module at 3.3V, though the
maximum supply voltage is 5.0V. The
connector J1 provides the audio input, gain
select, shutdown select, and power. (See
figure 1)
There are several suitable inputs for the
PmodAMP2. The typical input is a pulse width
modulated (PWM) signal produced by a digital
output from a Digilent programmable logic
system board or microcontroller board. The low
pass filter on the input acts as a reconstruction
filter to convert the PWM digital signal into an
analog voltage on the amplifier input.
The PmodAMP2 also accepts analog inputs
with an input voltage range of 0-Vcc. These
inputs will often be from an analog to digital
converter module, like the Digilent PmodDA1
or PmodDA2. The output of a digital to analog
Doc: 502-233
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page 1 of 2
PmodBT2™ Reference Manual
converter module will normally have a voltage
range of 0-3.3V and should have a sample rate
of at least 16Khz. The low pass filter on the
input removes the high frequency artifacts
generated during the sampling process.
Additionally, the PmodAMP2 accepts inputs
from a variety of line level audio signals. A line
level input, like the output of a portable CD
player or MP3 player, will typically be a 1V
peak-to-peak analog voltage. The input band-
pass filter clarifies and amplifies the input
voltage from the signal source and then directs
the signal to the output jack to drive a speaker.
The connector J2 operates as the speaker
output. (See figure 1)
Some older model Digilent boards may need
a Digilent Module Interface Board (MIB) and a
6-pin cable to connect to the PmodAMP2. The
MIB plugs into the system board and the cable
connects the PmodAMP2 to the MIB.
Note: For more information about the operation
and features of the Analog Devices SSM2377
Audio Amplifier integrated circuit please see
the datasheet available at
www.analog.com.
Functional Description
The gain on the PmodAMP2 may be selected
by tying the GAIN input to either logic ‘1’ or
logic ‘0’. (See table 1)
Table 1
GAIN Input
1
0
Gain
6 decibels (dB)
12 decibels (dB)
The PmodAMP2 features a micropower
shutdown mode with a typical shutdown
current of 100 nA. Users can enable the
shutdown by applying a logic low to the
SHUTDOWN
pin. A10K-ohm resistor pulls the
pin down to ground. To operate the AMP2
users must ensure the
SHUTDOWN
pin is in
the highest position.
Customers will generally use the PmodAMP2
module with a Digilent programmable logic
system board or microcontroller board. These
boards produce either a pulse width modulated
digital signal or an analog signal via a digital to
analog converter. Most Digilent system boards
have 6-pin connectors that allow the
PmodAMP2 to plug directly into the system
board or to connect via a Digilent 6-pin cable.
Doc: 502-233
page 2 of 2
Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.
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