ssm2211z-eval Analog Devices, Inc., ssm2211z-eval Datasheet - Page 20

• Manufacturer Part Number: ssm2211z-eval
• Description: Low Distortion 1.5 Watt Audio Power Amplifier
• Manufacturer: Analog Devices, Inc.

SSM2211
The polarity of the speakers is important, as each output is 180
degrees out of phase with the other. By connecting the minus
terminal of Speaker 1 to Pin 5, and the plus terminal of
Speaker 2 to Pin 8, proper speaker phase can be established.
The maximum power dissipation of the device, assuming both
loads are equal, can be found by doubling Equation 11. If the
loads are different, use Equation 11 to find the power dissipa-
tion caused by each load, then take the sum to find the total
power dissipated by the SSM2211.
EVALUATION BOARD
An evaluation board for the SSM2211 is available. For more
information, call 1-800-ANALOGD.
The voltage gain of the SSM2211 is given by Equation 20.
If desired, the input signal may be attenuated by turning the
10 kΩ potentiometer in the CW (clockwise ) direction. C
isolates the input common-mode voltage (V
and Pin 3. With V+ = 5 V, there is 2.5 V common-mode voltage
present at both output terminals, V
CAUTION: The ground lead of the oscilloscope probe, or any
other instrument used to measure the output signal, must not
be connected to either output, as this shorts out one of the
amplifier outputs and can possibly damage the device.
A safe method of displaying the differential output signal using a
grounded scope is shown in Figure 51. Connect Channel A probe
to the V
post. Invert Channel B, and add the two channels together. Most
multichannel oscilloscopes have this feature built in. If you must
connect the ground lead of the test instrument to either output
signal pins, a power-line isolation transformer must be used to
isolate the instrument ground from the power supply ground.
Recall that
AUDIO
INPUT
20kΩ POT.
VOLUME
V
A
V
=
O2
= 2
terminal post. Connect Channel B probe to the V
SHUTDOWN
P
×
R
×
R
F
Figure 50. Evaluation Board Schematic
I
CW
R
ON
1µF
C
IN
+
20kΩ
R
I
51kΩ
R1
1
2
3
4
SSM2211
O1
20kΩ
0.1µF
and V
R
V+
C1
F
6
7
+
O2
D
8
5
/2) present at Pin 2
, as well.
C2
10µF
J1
J2
C1
0.1µF
R
1W 8Ω
IN
L
O1
V
V
(20)
Rev. D | Page 20 of 24
O2
O1
Therefore, for P
8 V p­p. If the available input signal is 1.4 V rms or more, use
the board as is, with R
increase the value of R
When you have determined the closed-loop gain required by
your source level, and can develop 1 W across the 8 Ω load
resistor with the normal input signal level, replace the resistor
with your speaker. Your speaker can be connected across the
V
8 Ω load resistor is removed. For no phase inversion, V
be connected to the (+) terminal of the speaker.
To use the SSM2211 in a single-ended-output configuration,
replace J1 and J2 jumpers with electrolytic capacitors of a
suitable value, with the negative terminals to the output
terminals V
returned to ground. Note that the maximum output power is
reduced to 250 mW (one-quarter of the rated maximum), due
to the maximum swing in the nonbridged mode being one-half
and power being proportional to the square of the voltage. For
frequency response down 3 dB at 100 Hz, a 200 μF capacitor is
required with 8 Ω speakers.
The SSM2211 evaluation board also comes with a shutdown
switch, which allows the user to switch between on (normal
operation) and the power-conserving shutdown mode.
LFCSP PRINTED CIRCUIT BOARD LAYOUT
CONSIDERATIONS
The LFCSP is a plastic encapsulated package with a copper lead
frame substrate. This is a leadless package with solder lands on
the bottom surface of the package, instead of conventional
formed perimeter leads. A key feature that allows the user to
reach the quoted θ
paddle (DAP) on the bottom surface of the package. When
soldered to the PCB, the DAP can provide efficient conduction
of heat from the die to the PCB. In order to achieve optimum
package performance, consideration should be given to the PCB
pad design for both the solder lands and the DAP. For further
information the user is directed to the Amkor Technology
document, “Application Notes for Surface Mount Assembly of
Amkor’s MicroLead Frame (MLF) Packages. ” This can be
downloaded from the Amkor Technology website,
www.amkor.com, as a product application note.
O1
SSM2211
Figure 51. Using an Oscilloscope to Display the Bridged-Output Voltage
and V
O2
O1
posts for bridged-mode operation only after the
5
COMMON
8
MODE
and V
2.5V
O
= 1 W and R
JA
O2
performance is the exposed die attach
F
. The single-ended loads can then be
F
.
= R
8Ω
1W
I
GND
V
V
= 20 kΩ. If more gain is needed,
O2
O1
L
PROBES
= 8 Ω, V = 2.8 V rms, or
CH A
CH B
OSCILLOSCOPE
INV. ON
CH B
DISPLAY
A+B
O2
must