EVAL-SSM2306_15 Datasheet, PDF (3/8 Pages) Analog Devices – Evaluation Board for 2 W, Filterless, Class-D Stereo Audio Amplifier

EVAL-SSM2306
EVALUATION BOARD HARDWARE
Note that the SSM2306 evaluation board and layout guidelines
were developed by Gang Liu of Analog Technologies, Inc.,
Sunnyvale, CA.
SWITCHES
On the upper left corner of the evaluation board is an audio
stereo jack connector (3.5 mm), J1. The evaluation board uses
a conventional audio stereo signal connector/cable to receive
standard stereo audio signals from common appliances such as
DVD players, PCs, and TVs. Note that the two output signals
from the J1 connector are combined by a resistor network, R1
and R2, into a single signal. This connector provides single-ended
audio signals only. Therefore, when this input connector is used,
the S1E and S1F switches must be placed in the up position to
ac short-circuit the negative input ports to ground. This signal
path is shown in the schematic in Figure 6. Some appliances
have strong ground noise. If the audio source has strong ground
noise, do not use the J1 connector as the input connection
point. A single-ended input signal with strong ground noise can
generate an audible hissing sound at the output. If this problem
occurs, a differential mode connection is needed to cancel the
ground noise interference.
When differential mode audio signals are used as the input signal
source, use the headers 3HD1 and 3HD2 or use the soldering
pads located on the left side of the board. The top header (3HD1)
is for the left channel signals, and the lower header (3HD2) is
for the right channel. For differential mode, turn the S1E and
S1F switches to their off position (the down position).
There are two ground soldering pads on the lower left corner of
the evaluation board. At the bottom of the board is a switch bank;
the switch names and their corresponding functions are shown
in Table 1.
Table 1. Evaluation Board Switches
Switch Name
Function
S1A
AC-couple left channel, noninverting input
S1B
AC-couple left channel, inverting input
S1C
AC-couple right channel, inverting input
S1D
AC-couple right channel, noninverting input
S1E
AC ground left channel, inverting input
S1F
AC ground right channel, inverting input
S1H
Shutdown
When the S1A, S1B, S1C, and S1D switches are placed in the up
position, their corresponding coupling capacitors are shorted;
when these switches are placed in the down position, the coupling
capacitors are inserted in the signal paths.
The S1E and S1F switches are used to ac short-circuit the left and
right channel negative input ports to ground, respectively. This
function is generally recommended, but is only necessary when
driving the input ports in single-ended mode. After shorting
the negative input ports to ground, the noise picked up by the
input port connections is conducted to ground.
The S1H switch is for the shutdown function: the up position is
for shutdown, and the down position turns the amplifier on.
The upper right corner of the evaluation board has a dc power
jack connector, J2. The center pin is for the positive terminal.
The jack takes 2.5 V to 5.5 V voltage. With the input voltage at
5 V, the maximum peak current is approximately 1.2 A when
driving a 4 Ω load, and 0.6 A when driving an 8 Ω load.
There are two solder pads at the top center edge of the eval-
uation board for connecting the power supply voltages by
clipping or soldering.
All the output ports are located on the right side of the board
and are labeled. See the legend on the evaluation board and on
the schematic (Figure 6).
There are three ways to connect the output signals to the loads
(the loudspeakers): using the four 2-pin headers 2HD1 to
2HD4, using the terminal block, or using the soldering pads.
GETTING STARTED
To ensure proper operation, follow these steps carefully.
1. Verify that the control switches are set as follows:
• Shutdown control: S1H down. This activates the
amplifier.
• Audio source: S1E and S1F. For single-ended mode
(audio jack), place S1E and S1F in the up position.
• Input coupling: S1A, S1B, S1C, and S1D. For most
applications, ac-couple the inputs by placing these
switches in the down position.
2. Connect the loads to the proper output ports, depending
on the application. To connect the loads immediately after
the ferrite beads, use the OUTBL+, OUTBL−, OUTBR+,
and OUTBR− nodes. To connect the loads after the
inductors, use the OUTLL+, OUTLL−, OUTLR+, and
OUTLR− nodes.
3. Connect the power supply with the correct polarity and
proper voltage.
WHAT TO TEST
When implementing the SSM2306 evaluation board, test the
evaluation board for the following items:
• Electromagnetic interference (EMI). Connect wires for the
speakers in the same length as for the actual application
and perform the EMI test.
• Signal-to-noise ratio (SNR).
• Total harmonic distortion + noise (THD + N).
• Output noise. Use an A-weighting filter to filter the output
before the measurement meter.
• Maximum output power.
• Efficiency.
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