SSM2211SZ Analog Devices Inc, SSM2211SZ Datasheet - Page 15

• Manufacturer Part Number: SSM2211SZ
• Description: Audio Amp Speaker 1-CH Mono Class-AB 8-Pin SOIC N
• Manufacturer: Analog Devices Inc
• Type: Class ABr

Specifications of SSM2211SZ

• Package: 8SOIC N
• Function: Speaker
• Amplifier Type: Class-AB
• Maximum Output Power X Channels @ Load: 1.5x1@4Ohm W
• Total Harmonic Distortion Noise: 0.2@8Ohm@1W|0.1@8Ohm@0.35W %
• Typical Psrr: 66 dB
• Output Signal Type: Differential
• Rail To Rail: Rail to Rail Input
• Typical Gain Bandwidth Product: 4 MHz
• Maximum Load Resistance: 8 Ohm
• Output Type: 1-Channel Mono
• Max Output Power X Channels @ Load: 1.5W x 1 @ 4 Ohm
• Voltage - Supply: 2.7 V ~ 5.5 V
• Features: Differential Inputs, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Amplifier Class: AB
• No. Of Channels: 1
• Output Power: 1.5W
• Supply Voltage Range: 2.7V To 5.5V
• Load Impedance: 8ohm
• Operating Temperature Range: -20°C To +85°C
• Amplifier Case Style: SOIC
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TYPICAL APPLICATIONS
Figure 42 shows how the SSM2211 is connected in a typical
application. The SSM2211 can be configured for gain much like
a standard operational amplifier. The gain from the audio input
to the speaker is
The 2× factor results from Pin 8 having an opposite polarity of
Pin 5, providing twice the voltage swing to the speaker from the
bridged-output (BTL) configuration.
C
filtering. Pin 2 is connected to Pin 3 to provide an offset voltage
for single-supply use, with C
ground to enhance power-supply rejection. Because Pin 4 is a
virtual ac ground, the input impedance is equal to R
input coupling capacitor, which also creates a high-pass filter
with a corner frequency of
Because the SSM2211 has an excellent phase margin, a feedback
capacitor in parallel with R
required, as it is in some competitor products.
BRIDGED OUTPUT VS. SINGLE-ENDED OUTPUT
CONFIGURATIONS
The power delivered to a load with a sinusoidal signal can be
expressed in terms of the peak voltage of the signal and the
resistance of the load as
By driving a load from a BTL configuration, the voltage swing
across the load doubles. Therefore, an advantage in using a BTL
configuration becomes apparent from Equation 3, as doubling
the peak voltage results in four times the power delivered to the
load. In a typical application operating from a 5 V supply, the
maximum power that can be delivered by the SSM2211 to an
8 Ω speaker in a single-ended configuration is 250 mW. By
S
AUDIO
INPUT
is a supply bypass capacitor used to provide power supply
P
A
f
HP
L
V
=
= 2
=
2
V
2
×
×
C
PK
π
C
R
R
R
R
2
L
I
F
I
1
R
×
Figure 42. Typical Configuration
I
C
C
4
3
C
B
–
+
SSM2211
F
2
to band limit the amplifier is not
B
6
providing a low ac impedance to
5V
7
R
1
F
C
S
5
8
–
+
I
. C
SPEAKER
C
8V
is the
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driving this speaker with a bridged output, 1 W of power can be
delivered. This translates to a 12 dB increase in sound pressure
level from the speaker.
Driving a speaker differentially from a BTL offers another
advantage in that it eliminates the need for an output coupling
capacitor to the load. In a single-supply application, the quiescent
voltage at the output is half of the supply voltage. If a speaker is
connected in a single-ended configuration, a coupling capacitor
is needed to prevent dc current from flowing through the speaker.
This capacitor also needs to be large enough to prevent low
frequency roll-off. The corner frequency is given by
where R
capacitance.
For an 8 Ω speaker and a corner frequency of 20 Hz, a 1000 μF
capacitor is needed, which is physically large and costly. By
connecting a speaker in a BTL configuration, the quiescent
differential voltage across the speaker becomes nearly zero,
eliminating the need for the coupling capacitor.
SPEAKER EFFICIENCY AND LOUDNESS
The effective loudness of 1 W of power delivered into an 8 Ω
speaker is a function of speaker efficiency. The efficiency is
typically rated as the sound pressure level (SPL) at 1 meter in
front of the speaker with 1 W of power applied to the speaker.
Most speakers are between 85 dB and 95 dB SPL at 1 meter at
1 W. Table 7 shows a comparison of the relative loudness of
different sounds.
Table 7. Typical Sound Pressure Levels
Source of Sound
Threshold of Pain
Heavy Street Traffic
Cabin of Jet Aircraft
Average Conversation
Average Home at Night
Quiet Recording Studio
Threshold of Hearing
Consequently, Table 7 demonstrates that 1 W of power into a
speaker can produce quite a bit of acoustic energy.
f
−
3
L
dB
is the speaker resistance and C
=
π 2
R
L
1
×
C
C
SPL (dB)
120
95
80
65
50
30
0
C
is the coupling
SSM2211
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