SSM2356CBZ-RL Analog Devices Inc, SSM2356CBZ-RL Datasheet - Page 13

• Manufacturer Part Number: SSM2356CBZ-RL
• Description: 2x2W Filterless Class D Stereo Audio Amp
• Manufacturer: Analog Devices Inc
• Type: Class Dr

Specifications of SSM2356CBZ-RL

• Output Type: 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 2.5W x 2 @ 4 Ohm
• Voltage - Supply: 2.5 V ~ 5.5 V
• Features: Depop, Differential Inputs, Short-Circuit and Thermal Protection, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 16-WLCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
OVERVIEW
The SSM2356 stereo Class-D audio amplifier features a filterless
modulation scheme that greatly reduces the external component
count, conserving board space and, thus, reducing systems cost.
The SSM2356 does not require an output filter but, instead,
relies on the inherent inductance of the speaker coil and the
natural filtering of the speaker and human ear to fully recover
the audio component of the square wave output. Most Class-D
amplifiers use some variation of pulse-width modulation
(PWM), but the SSM2356 uses Σ-Δ modulation to determine
the switching pattern of the output devices, resulting in a number
of important benefits. Σ-Δ modulators do not produce a sharp
peak with many harmonics in the AM frequency band, as pulse-
width modulators often do. Σ-Δ modulation provides the
benefits of reducing the amplitude of spectral components at
high frequencies, that is, reducing EMI emission that might
otherwise be radiated by speakers and long cable traces. Due to
the inherent spread-spectrum nature of Σ-Δ modulation, the
need for oscillator synchronization is eliminated for designs
incorporating multiple SSM2356 amplifiers.
The SSM2356 also integrates overcurrent and temperature
protection.
GAIN SELECTION
The preset gain of SSM2356 can be selected between 6 dB and
18 dB with no external components and no change to the input
impedance. A major benefit of fixed input impedance is that
there is no need to recalculate input corner frequency (Fc)
when gain is adjusted. The same input coupling components
can be used for both gain settings.
It is possible to adjust the SSM2356 gain by using external
resistors at the input. To set a gain lower than 18 dB (or 6 dB
when GAIN = V
configuration and Figure 35 for the single-ended configuration.
Calculate the external gain configuration as follows:
When GAIN = GND
When GAIN = V
POP-AND-CLICK SUPPRESSION
Voltage transients at the output of audio amplifiers may occur
when shutdown is activated or deactivated. Voltage transients
as low as 10 mV can be heard as an audio pop in the speaker.
Clicks and pops can also be classified as undesirable audible
transients generated by the amplifier system and, therefore, as
not coming from the system input signal.
Such transients may be generated when the amplifier system
changes its operating mode. For example, the following can be
sources of audible transients:
External Gain Settings = 160 kΩ/(80 kΩ + R
External Gain Settings = 640 kΩ/(80 kΩ + R
DD
DD
), refer to Figure 34 for the differential input
EXT
EXT
)
)
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The SSM2356 has a pop-and-click suppression architecture that
reduces these output transients, resulting in noiseless activation and
deactivation.
EMI NOISE
The SSM2356 uses a proprietary modulation and spread-
spectrum technology to minimize EMI emissions from the
device. For applications having difficulty passing FCC Class B
emission tests, the SSM2356 includes a modulation select pin
(ultralow EMI emission mode) that significantly reduces the
radiated emissions at the Class-D outputs, particularly above
100 MHz. Figure 36 shows SSM2356 EMI emission tests per-
formed in a certified FCC Class-B laboratory in normal
emissions mode (EDGE = GND). Figure 37 shows SSM2356
EMI emission with EDGE = V
emissions mode.
System power-up/power-down
Mute/unmute
Input source change
Sample rate change
Figure 36. EMI Emissions from SSM2356, 1-Channel, 12 cm Cable,
Figure 37. EMI Emissions from SSM2356, 1-Channel, 12 cm Cable,
60
50
40
30
20
10
60
50
40
30
20
10
0
0
30
30
130
130
230
230
330
330
FREQUENCY (MHz)
FREQUENCY (MHz)
EDGE = GND
EDGE = V
430
430
DD
, placing the device in low
530
530
DD
630
630
[1] HORIZONTAL
[2] VERTICAL
FCC CLASS-B LIMIT
[1] HORIZONTAL
[2] VERTICAL
FCC CLASS-B LIMIT
730
730
830
830
SSM2356
930 1000
930 1000