SSM2211_02 Ver la hoja de datos (PDF) - Analog Devices
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SSM2211_02 Datasheet PDF : 16 Pages
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SSM2211
To summarize the final design:
VDD
R1
RF
CC
CB
Max. TA
5V
20 kW
28 kW
2.2 mF
2.2 mF
85∞C
Single Ended Applications
There are applications where driving a speaker differentially is
not practical. An example would be a pair of stereo speakers
where the minus terminal of both speakers is connected to
ground. Figure 8 shows how this can be accomplished.
10k⍀
5V
AUDIO
INPUT
10k⍀
0.47F
6
4–
5
SSM2211
3+
8
1
7
2
470F +
0.1F
–
250mW
SPEAKER
(8⍀)
Figure 8. A Single Ended Output Application
It is not necessary to connect a dummy load to the unused output
to help stabilize the output. The 470 mF coupling capacitor cre-
ates a high pass frequency cutoff as given in Equation 4 of 42 Hz,
which is acceptable for most computer speaker applications.
The overall gain for a single ended output configuration is
AV = RF/R1, which for this example is equal to 1.
Driving Two Speakers Single Endedly
It is possible to drive two speakers single endedly with both out-
puts of the SSM2211.
AUDIO
INPUT
20k⍀
20k⍀
1F
5V
6
4–
5
SSM2211
3+
8
1
7
2
470F –
+
470F +
0.1F
–
LEFT
SPEAKER
(8⍀)
RIGHT
SPEAKER
(8⍀)
Figure 9. SSM2211 Used as a Dual Speaker Amplifier
Each speaker is driven by a single ended output. The trade-off is
that only 250 mW sustained power can be put into each
speaker. Also, a coupling capacitor must be connected in series
with each of the speakers to prevent large DC currents from
flowing through the 8 W speakers. These coupling capacitors
will produce a high pass filter with a corner frequency given by
Equation 4. For a speaker load of 8 W and a coupling capacitor
of 470 mF, this results in a –3 dB frequency of 42 Hz.
Because the power of a single ended output is one quarter that of a
bridged output, both speakers together would still be half as loud
(–6 dB SPL) as a single speaker driven with a bridged output.
The polarity of the speakers is important, as each output is 180∞
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 can be found by
doubling Equation 11, assuming both loads are equal. 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. Contact your
local sales representative or call 1-800-ANALOGD for more in-
formation.
SHUTDOWN
R1
51k⍀
V+
+ C2
10F
AUDIO
INPUT
VOLUME
20k⍀ POT.
ON
+
CIN
1F
CW
RIN
20k⍀
6
J1
1
8
2 SSM2211
3
4
7
5 J2
RF
20k⍀
C1
0.1F
V02
RL
1W 8⍀
V01
C1
0.1F
Figure 10. Evaluation Board Schematic
The voltage gain of the SSM2211 is given by Equation 20 below:
AV
=2¥
RF
RIN
(20)
If desired, the input signal may be attenuated by turning the
10 kW potentiometer in the CW direction. CIN isolates the input
common mode voltage (V+/2) present at Pin 2 and 3. With
V+ = 5 V, there is 2.5 V common-mode voltage present at both
output terminals VO1 and VO2 as well.
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 would short out one of the
amplifier’s outputs and possibly damage the device.
A safe method of displaying the differential output signal using a
grounded scope is shown in Figure 11. Simply connect the Chan-
nel A probe to VO2 terminal post, connect the Channel B probe to
VO1 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 out-
put signal pins, a power line isolation transformer must be used to
isolate the instrument ground from power supply ground.
REV. B
–13–
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