EVAL-SSM2301_15 Datasheet, PDF (3/8 Pages) Analog Devices – Evaluation Board for Filterless Class-D Audio Amplifier

EVALUATION BOARD HARDWARE
Note that the SSM2301 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. It accepts standard stereo
audio signals by using a conventional audio stereo signal
connector/cable to receive audio signals from common
appliances such as DVD players, personal computers, 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.
When this input connector is utilized, turn the switch, S1C, to
the upper position to short circuit the negative input node to
ground, essentially creating a single-ended input signal. S1C, in
the upper position, blocks any interference shown on this
floating node. This signal path is shown in the schematic in
Figure 7. Some appliances may have strong ground noise. In the
event that 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 generates an audible
hissing sound at the output. When this happens, differential
mode connection is needed and the ground noise interference
can be cancelled.
The input signal can be connected in a differential mode using
the HD1 (Header 1) connector or the solder pads on the left
side of the board. Note that the S1C switch should be turned off
(placed in the lower position) for differential input mode. See
Figure 7 and Figure 8. The solder pads on the left edge of the
board can conveniently be connected by using alligator clips.
Figure 3 shows such a connection: the ground on the signal
source appliance is sensed by a dedicated cable wire in addition
to the ground connection wire.
TWIST OR SHIELD
SIGNAL
SOURCE
OUTPUT
GND
GND
INPUT+
INPUT– EVALUATION
BOARD
GND
Figure 3. Cancelling Ground Noise by Differential Input Mode
The SSM2301 evaluation board has two ground soldering pads
on the lower left corner. They can be used for connection to the
ground of the signal source, as indicated in Figure 3.
The lower side of the board has a switch bank with the follow-
ing functions:
• S1A
Upper position: short circuits the input coupling capacitor
for positive input port.
Lower position: open circuits the input coupling capacitor
for positive input port.
EVAL-SSM2301
• S1B
The same functions as the S1A switch but for the coupling
capacitor connected to the negative input port.
• S1C
Upper position: short circuits the ac signal on the negative
input port to ground. This function is only needed when
driving the input port in single-ended mode, such as by
using the audio jack.
Lower position: differential input.
• S1D (marked with GAIN)
Upper position: For controlling the gain, short circuits the
GAIN pin to ground, setting the amplifier to a lower gain,
6 dB.
Lower position: sets the amplifier to a higher gain, 12 dB.
• S1E (marked with SD)
Upper position: shuts down the amplifier for the shutdown
functions.
Lower position: activates the amplifier.
The upper right corner of the SSM2301 evaluation board has a
dc power jack connector. The center pin is for the positive
terminal. The SSM2301 can operate from 2.5 V to 5 V supply
voltage. The maximum peak current is approximately 0.6 A
when driving an 8 Ω load with a 5 V supply. The SSM2301
evaluation board also has two solder pads in the upper center
edge area for connecting the power supply voltages by clipping
with alligator clips or soldering wires.
The output ports are located on the right side of the board.
There are three options to connect the output ports to a load:
screw terminal (TB1), header (HD3), or the soldering pads on
the right edge of the board. Header HD4, which is also on the
right side of the board, is solely a ground connection point and
not associated with load connection to the output (see Figure 7
and Figure 8).
GETTING STARTED
To ensure proper operation, follow these steps carefully.
1. Verify that the control switches are set at the proper positions.
• Shutdown control: S1E down. This activates the
amplifier.
• Gain setting: S1D. Select the position based on the
gain needed.
• Audio source: S1C. For single-ended mode (audio
jack), be sure to put S1C in the upper position.
• Input coupling: S1A/S1B. For most applications, ac
couple the inputs by setting these switches in the
lower position.
2. Connect load across output ports.
3. Connect the power supply with the correct polarity and
proper voltage.
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