2 W, Filterless, Class-D Stereo Audio Amplifier SSM2306

2 W, Filterless, Class-D
Stereo Audio Amplifier
SSM2306
The SSM2306 features ultralow idle current, high efficiency, and
a low noise modulation scheme. It operates with >87% efficiency
at 1.4 W into 8 Ω from a 5.0 V supply and has a signal-to-noise
ratio (SNR) that is better than 96 dB. PDM modulation offers lower
EMI radiated emissions compared to other Class-D architectures.
FEATURES
Filterless Class-D amplifier with built-in output stage
2 W into 4 Ω and 1.4 W into 8 Ω at 5.0 V supply
Ultralow idle current with load resistance
>87% efficiency at 5.0 V, 1.4 W into 8 Ω speaker
Better than 96 dB SNR (signal-to-noise ratio)
Available in 16-lead, 3 mm × 3 mm LFCSP
Single-supply operation from 2.5 V to 5.0 V
20 nA ultralow shutdown current
Short-circuit and thermal protection
Pop-and-click suppression
Built-in resistors reduce board component count
Default fixed 18 dB gain and user-adjustable
The SSM2306 has a micropower shutdown mode with a typical
shutdown current of 20 nA. Shutdown is enabled by applying a
logic low to the SD pin.
The architecture of the device allows it to achieve a very low level
of pop and click to minimize voltage glitches at the output
during turn-on and turn-off, thereby reducing audible noise on
activation and deactivation. The fully differential input of the
SSM2306 provides excellent rejection of common-mode noise
on the input. Input coupling capacitors can be omitted if the dc
input common-mode voltage is approximately VDD/2.
APPLICATIONS
Mobile phones
MP3 players
Portable gaming
Portable electronics
Educational toys
Notebook computers
The SSM2306 also has excellent rejection of power supply noise,
including noise caused by GSM transmission bursts and RF
rectification.
www.BDTIC.com/ADI
The SSM2306 has a preset gain of 18 dB that can be reduced by
using external resistors.
GENERAL DESCRIPTION
The SSM2306 is a fully integrated, high efficiency, Class-D stereo
audio amplifier designed to maximize performance for portable
applications. The application circuit requires minimum external
components and operates from a single 2.5 V to 5.0 V supply. It
is capable of delivering 2 W of continuous output power with less
than 10% THD + N driving a 4 Ω load from a 5.0 V supply.
The SSM2306 is specified over the commercial temperature range
(−40°C to +85°C). It has built-in thermal shutdown and output
short-circuit protection. It is available in a 16-lead, 3 mm × 3 mm
lead frame chip scale package (LFCSP).
FUNCTIONAL BLOCK DIAGRAM
VBATT
2.5V TO 5.0V
10µF
0.1µF
22nF1
RIGHT IN+
SSM2306
REXT
344kΩ
22nF1
REXT
VDD
OUTR+
INR+
RIGHT IN–
VDD
43kΩ
INR–
MODULATOR
FET
DRIVER
OUTR–
43kΩ
344kΩ
SHUTDOWN
BIAS
SD
INTERNAL
OSCILLATOR
344kΩ
LEFT IN+
REXT
43kΩ
OUTL+
INL+
LEFT IN–
22nF1
REXT
INL–
GAIN = 344kΩ/(43kΩ + REXT )
MODULATOR
FET
DRIVER
OUTL–
43kΩ
344kΩ
1 INPUT CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY VDD/2.
GND
GND
06542-001
22nF1
Figure 1.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2007 Analog Devices, Inc. All rights reserved.
SSM2306
TABLE OF CONTENTS
Features .............................................................................................. 1
Typical Application Circuits ......................................................... 11
Applications....................................................................................... 1
Application Notes ........................................................................... 12
General Description ......................................................................... 1
Overview ..................................................................................... 12
Functional Block Diagram .............................................................. 1
Gain Selection............................................................................. 12
Revision History ............................................................................... 2
Pop-and-Click Suppression ...................................................... 12
Specifications..................................................................................... 3
EMI Noise.................................................................................... 12
Absolute Maximum Ratings............................................................ 4
Layout .......................................................................................... 13
Thermal Resistance ...................................................................... 4
Input Capacitor Selection.......................................................... 13
ESD Caution.................................................................................. 4
Proper Power Supply Decoupling ............................................ 13
Pin Configuration and Function Descriptions............................. 5
Outline Dimensions ....................................................................... 14
Typical Performance Characteristics ............................................. 6
Ordering Guide .......................................................................... 14
REVISION HISTORY
4/07—Revision 0: Initial Version
www.BDTIC.com/ADI
Rev. 0 | Page 2 of 16
SSM2306
SPECIFICATIONS
VDD = 5.0 V; TA = 25oC; RL = 4 Ω, 8 Ω; gain = 6 dB, unless otherwise noted.
Table 1.
Parameter
DEVICE CHARACTERISTICS
Output Power
Symbol
Conditions
PO
RL = 4 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V
RL = 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V
RL = 4 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V
RL = 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V
RL = 4 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
RL = 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
RL = 4 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V
RL = 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V
RL = 4 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V
RL = 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V
RL = 4 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
RL = 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
POUT = 2 W, 4 Ω, VDD = 5.0 V
POUT = 1.4 W, 8 Ω, VDD = 5.0 V
PO = 2 W into 4 Ω each channel, f = 1 kHz, VDD = 5.0 V
PO = 1 W into 8 Ω each channel, f = 1 kHz, VDD = 5.0 V
Efficiency
η
Total Harmonic Distortion + Noise
THD + N
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
VCM
CMRRGSM
Min
XTALK
fSW
VOOS
70
W
W
W
W
W
W
W
W
W
W
W
W
%
%
%
%
V
dB
78
420
2.0
dB
kHz
mV
1.0
VCM = 2.5 V ± 100 mV at 217 Hz, G = 18 dB, input
referred
PO = 100 mW , f = 1 kHz
VDD − 1
Supply Current
ISY
Shutdown Current
ISD
GAIN
Closed-Loop Gain
Differential Input Impedance
Av
ZIN
REXT = 0
SD = VDD
18
43
dB
kΩ
SHUTDOWN CONTROL
Input Voltage High
Input Voltage Low
Turn-On Time
Turn-Off Time
Output Impedance
VIH
VIL
tWU
tSD
OUT
ISY ≥ 1 mA
ISY ≤ 300 nA
SD rising edge from GND to VDD
SD falling edge from VDD to GND
SD = GND
1.2
0.5
30
5
>100
V
V
ms
μs
kΩ
NOISE PERFORMANCE
Output Voltage Noise
en
VDD = 3.6 V, f = 20 Hz to 20 kHz, inputs are
ac-grounded, AV = 18 dB, RL = 4 Ω, A weighting
POUT = 2.0 W, RL = 4 Ω
44
μV
96
dB
SNR
Rev. 0 | Page 3 of 16
2.5
70
Unit
Guaranteed from PSRR test
VDD = 2.5 V to 5.0 V
VRIPPLE = 100 mV rms at 217 Hz, inputs ac GND,
CIN = 0.1 μF, input referred
VIN = 0 V, no load, VDD = 5.0 V
VIN = 0 V, no load, VDD = 3.6 V
VIN = 0 V, no load, VDD = 2.5 V
SD = GND
Signal-to-Noise Ratio
VDD
PSRR
PSRRGSM
Max
1.8
1.4
0.9
0.615
0.35
0.275
2.4
1.53
1.1
0.77
0.45
0.35
75
85
0.4
0.02
www.BDTIC.com/ADI
Channel Separation
Average Switching Frequency
Differential Output Offset Voltage
POWER SUPPLY
Supply Voltage Range
Power Supply Rejection Ratio
Typ
85
75
5.0
V
dB
dB
6.5
5.7
5.1
20
mA
mA
mA
nA
SSM2306
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings apply at 25°C, unless otherwise noted.
THERMAL RESISTANCE
Table 2.
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Parameter
Supply Voltage
Input Voltage
Common-Mode Input Voltage
ESD Susceptibility
Storage Temperature Range
Operating Temperature Range
Junction Temperature Range
Lead Temperature (Soldering, 60 sec)
Rating
6V
VDD
VDD
4 kV
−65°C to +150°C
−40°C to +85°C
−65°C to +165°C
300°C
Table 3. Thermal Resistance
Package Type
16-Lead, 3 mm × 3 mm LFCSP
ESD CAUTION
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
www.BDTIC.com/ADI
Rev. 0 | Page 4 of 16
θJA
44
θJC
31.5
Unit
°C/W
SSM2306
12 OUTR+
11 OUTR–
10 NC
14 VDD
NC = NO CONNECT
06542-002
9 INR+
INR– 8
NC 7
TOP VIEW
(Not to Scale)
INL– 5
INL+ 4
SSM2306
NC 6
SD 3
13 GND
PIN 1
INDICATOR
OUTL+ 1
OUTL– 2
15 VDD
16 GND
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Mnemonic
OUTL+
OUTL−
SD
INL+
INL−
NC
NC
INR−
INR+
NC
OUTR−
OUTR+
GND
VDD
VDD
GND
Description
Inverting Output for Left Channel.
Noninverting Output for Left Channel.
Shutdown Input. Active low digital input.
Noninverting Input for Left Channel.
Inverting Input for Left Channel.
No Connect.
No Connect.
Inverting Input for Right Channel.
Noninverting Input for Right Channel.
No Connect.
Noninverting Output for Right Channel.
Inverting Output for Right Channel.
Ground for Output Amplifiers.
Power Supply for Output Amplifiers.
Power Supply for Output Amplifiers.
Ground for Output Amplifiers.
www.BDTIC.com/ADI
Rev. 0 | Page 5 of 16
SSM2306
TYPICAL PERFORMANCE CHARACTERISTICS
100
THD + N (%)
VDD = 3.6V
0.1
0.001
0.0001
0.001
0.01
0.1
1
1
VDD = 3.6V
0.1
VDD = 5V
VDD = 5V
0.01
10
OUTPUT POWER (W)
0.001
0.0001
06542-003
THD + N (%)
1
0.01
0.01
0.1
100
VDD = 2.5V
10
100k
VDD = 5V
RL = 8Ω, 33µH
AV = 18dB
10
THD + N (%)
1
1
www.BDTIC.com/ADI
VDD = 3.6V
0.1
1
Figure 6. THD + N vs. Output Power into 8 Ω, AV = 6 dB
RL = 8Ω, 33µH
AV = 18dB
10
0.001
OUTPUT POWER (W)
Figure 3. THD + N vs. Output Power into 4 Ω, AV = 18 dB
THD + N (%)
VDD = 2.5V
10
10
100
RL = 8Ω, 33µH
AV = 6dB
VDD = 2.5V
06542-006
RL = 4Ω, 33µH
AV = 18dB
06542-007
100
0.1
1W
0.25W
0.01
0.01
VDD = 5V
0.5W
0.001
0.01
0.1
1
10
OUTPUT POWER (W)
0.001
10
06542-004
0.001
0.0001
VDD = 2.5V
10
VDD = 5V
AV = 18dB
RL = 4Ω, 33µH
1
THD + N (%)
10
VDD = 3.6V
VDD = 5V
0.1
2W
1
0.1
1W
0.5W
0.01
0.001
0.0001
0.001
0.01
0.1
1
OUTPUT POWER (W)
10
0.001
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 8. THD + N vs. Frequency, VDD = 5 V, RL = 4 Ω, AV = 18 dB
Figure 5. THD + N vs. Output Power into 4 Ω, AV = 6 dB
Rev. 0 | Page 6 of 16
06542-008
0.01
06542-005
THD + N (%)
10k
Figure 7. THD + N vs. Frequency, VDD = 5 V, RL = 8 Ω, AV = 18 dB
100
RL = 4Ω, 33µH
AV = 6dB
1k
FREQUENCY (Hz)
Figure 4. THD + N vs. Output Power into 8 Ω, AV = 18 dB
100
100
SSM2306
100
VDD = 3.6V
AV = 18dB
RL = 8Ω, 33µH
10
10
1
1
THD + N (%)
0.1
VDD = 2.5V
AV = 18dB
RL = 4Ω, 33µH
0.5W
0.1
0.25W
0.5W
0.125W
0.01
0.01
0.125W
100
1k
10k
100k
FREQUENCY (Hz)
100
1k
10k
100k
FREQUENCY (Hz)
Figure 12. THD + N vs. Frequency, VDD = 2.5 V, RL = 4 Ω, AV = 18 dB
Figure 9. THD + N vs. Frequency, VDD = 3.6 V, RL = 8 Ω, AV = 18 dB
100
0.25W
0.001
10
06542-009
0.001
10
06542-012
THD + N (%)
100
7.5
VDD = 3.6V
AV = 18dB
RL = 4Ω, 33µH
ISY FOR BOTH CHANNELS
7.0
SUPPLY CURRENT (mA)
THD + N (%)
10
1W
1
0.1
0.5W
RL = 8Ω, 33µH
6.5
RL = 4Ω, 33µH
6.0
NO LOAD
5.5
www.BDTIC.com/ADI
0.25W
0.01
5.0
1k
10k
100k
FREQUENCY (Hz)
4.0
2.5
4.5
5.0
5.5
0.8
12
10
SUPPLY CURRENT (µA)
10
THD + N (%)
4.0
Figure 13. Supply Current vs. Supply Voltage, No Load
VDD = 2.5V
AV = 18dB
RL = 8Ω, 33µH
1
0.1
0.25W
0.125W
0.075W
8
VDD = 5V
6
VDD = 3.6V
4
VDD = 2.5V
2
100
1k
10k
100k
FREQUENCY (Hz)
06542-011
0.01
0.001
10
3.5
SUPPLY VOLTAGE (V)
Figure 10. THD + N vs. Frequency, VDD = 3.6 V, RL = 4 Ω, AV = 18 dB
100
3.0
06542-013
100
06542-010
0.001
10
06542-014
4.5
Figure 11. THD + N vs. Frequency, VDD = 2.5 V, RL = 8 Ω, AV = 18 dB
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
SHUTDOWN VOLTAGE (V)
Figure 14. Supply Current vs. Shutdown Voltage
Rev. 0 | Page 7 of 16
SSM2306
3.0
2.5
1.8
f = 1kHz
AV = 18dB
RL = 4Ω, 33µH
f = 1kHz
A = 6dB
1.6 RV = 8Ω, 33µH
L
OUTPUT POWER (W)
OUTPUT POWER (W)
1.4
2.0
10%
1.5
1%
1.0
1.2
10%
1.0
1%
0.8
0.6
0.4
0.5
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
Figure 15. Maximum Output Power vs. Supply Voltage, RL = 4 Ω, AV = 18 dB
3.0
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
Figure 18. Maximum Output Power vs. Supply Voltage, RL = 8 Ω, AV = 6 dB
100
f = 1kHz
AV = 6dB
RL = 4Ω, 33µH
RL = 4Ω, 33µH
90
80
70
2.0
EFFICIENCY (%)
OUTPUT POWER (W)
2.5
0
2.5
06542-015
0
2.5
06542-018
0.2
10%
1.5
1%
60
VDD = 5V
VDD = 3.6V
VDD = 2.5V
50
40
www.BDTIC.com/ADI
1.0
30
20
0.5
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
0
06542-016
0
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Figure 19. Efficiency vs. Output Power into 4 Ω
100
1.8
f = 1kHz
A = 18dB
1.6 RV = 8Ω, 33µH
L
RL = 8Ω, 33µH
90
80
1.4
70
1.2
1.0
EFFICIENCY (%)
OUTPUT POWER (W)
0.4
OUTPUT POWER (W)
Figure 16.Maximum Output Power vs. Supply Voltage, RL = 4 Ω, AV = 6 dB
10%
0.8
1%
0.6
VDD = 2.5V
VDD = 5V
VDD = 3.6V
60
50
40
30
0.4
20
0.2
10
3.0
3.5
4.0
SUPPLY VOLTAGE (V)
4.5
5.0
06542-017
0
2.5
0.2
Figure 17. Maximum Output Power vs. Supply Voltage, RL = 8 Ω, AV = 18 dB
Rev. 0 | Page 8 of 16
0
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
OUTPUT POWER (W)
Figure 20. Efficiency vs. Output Power into 8 Ω
1.8
06542-020
0
2.5
06542-019
10
SSM2306
2.2
1.4
VDD = 5V
RL= 8Ω, 33µH
FOR BOTH CHANNELS
1.8
POWER DISSIPATION (W)
POWER DISSIPATION (W)
1.2
VDD = 3.6V
RL = 4Ω, 33µH
FOR BOTH CHANNELS
2.0
1.0
0.8
0.6
0.4
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
OUTPUT POWER (W)
0
06542-021
0
OUTPUT POWER (W)
Figure 24. Power Dissipation vs. Output Power at VDD = 3.6 V, RL = 4 Ω
Figure 21. Power Dissipation vs. Output Power at VDD = 5 V, RL = 8 Ω
900
1.0
VDD = 3.6V
RL = 8Ω, 33µH
FOR BOTH CHANNELS
0.9
700
0.7
600
ISY (mA)
0.6
0.5
0.4
VDD = 3.6V
500
VDD = 2.5V
400
www.BDTIC.com/ADI
200
0.2
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
OUTPUT POWER (W)
0
0
2.4
1300
0.8
1.0
1.2
1.4
1.6
VDD = 5V
RL = 4Ω, 33µH
ISY IS FOR BOTH CHANNELS
1200
VDD = 3.6V
1100
2.2
1000
2.0
900
1.8
800
ISY (mA)
1.6
1.4
1.2
VDD = 2.5V
700
600
0.8
400
0.6
300
0.4
200
0.2
100
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
OUTPUT POWER (W)
Figure 23. Power Dissipation vs. Output Power at VDD = 5 V, RL = 4 Ω
0
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
PO (W)
Figure 26. Supply Current vs. Output Power into 4 Ω
Rev. 0 | Page 9 of 16
2.2
06542-026
500
1.0
06542-023
POWER DISSIPATION (W)
0.6
Figure 25. Supply Current vs. Output Power into 8 Ω
VDD = 5V
RL = 4Ω, 33µH
FOR BOTH CHANNELS
2.6
0.4
PO (W)
Figure 22. Power Dissipation vs. Output Power at VDD = 3.6 V, RL = 8 Ω
2.8
0.2
06542-025
100
0.1
0
VDD = 5V
300
0.3
06542-022
POWER DISSIPATION (W)
RL = 8Ω, 33µH
ISY IS FOR BOTH CHANNELS
800
0.8
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
06542-024
0.2
0
SSM2306
0
7
–10
6
–20
5
4
VOLTAGE (V)
–40
–50
–60
SD INPUT
2
1
–70
OUTPUT
0
–80
100
1k
10k
100k
FREQUENCY (Hz)
–2
–10
06542-027
10
0
20
30
40
50
60
70
80
90
140
160
180
TIME (ms)
Figure 27. PSRR vs. Frequency
0
10
06542-030
–1
–90
–100
3
06542-031
PSRR (dB)
–30
Figure 30. Turn-On Response
7
RL = 8Ω, 33µH
OUTPUT
6
–10
SD INPUT
5
–20
VOLTAGE (V)
–40
–50
0
–70
–1
10
100
1k
10k
100k
FREQUENCY (Hz)
0
VDD = 3.6V
VRIPPLE = 1V rms
–20 RL = 8Ω, 33µH
–60
–80
–100
–120
100
1k
10k
FREQUENCY (Hz)
100k
06542-029
CROSSTALK (dB)
–40
10
–2
–20
0
20
40
60
80
100
120
TIME (ms)
Figure 31. Turn-Off Response
Figure 28. CMRR vs. Frequency
–140
2
www.BDTIC.com/ADI
–60
–80
3
1
06542-028
CMRR (dB)
4
–30
Figure 29. Crosstalk vs. Frequency
Rev. 0 | Page 10 of 16
SSM2306
TYPICAL APPLICATION CIRCUITS
10µF
0.1µF
SSM2306
22nF1
RIGHT IN+
REXT
VDD
22nF1
OUTR+
SD
22nF1
REXT
BIAS
22nF1
OUTR–
INTERNAL
OSCILLATOR
OUTL+
INL+
FET
DRIVER
MODULATOR
INL–
LEFT IN–
FET
DRIVER
MODULATOR
REXT
SHUTDOWN
LEFT IN+
VDD
INR+
INR–
RIGHT IN–
VBATT
2.5V TO 5.0V
OUTL–
REXT
GND
06542-037
GND
1 INPUT
CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY VDD/2.
Figure 32. Stereo Differential Input Configuration
www.BDTIC.com/ADI
10µF
0.1µF
SSM2306
22nF
RIGHT IN
REXT
VDD
OUTR+
MODULATOR
SD
22nF
REXT
BIAS
OUTR–
INTERNAL
OSCILLATOR
INL+
INL–
OUTL+
MODULATOR
FET
DRIVER
OUTL–
REXT
GND
GND
06542-038
22nF
FET
DRIVER
REXT
SHUTDOWN
LEFT IN
VDD
INR+
INR–
22nF
VBATT
2.5V TO 5.0V
Figure 33. Stereo Single-Ended Input Configuration
Rev. 0 | Page 11 of 16
SSM2306
APPLICATION NOTES
OVERVIEW
EMI NOISE
The SSM2306 stereo, Class-D, audio amplifier features a filterless
modulation scheme that greatly reduces the external components count, conserving board space and, thus, reducing systems
cost. The SSM2306 does not require an output filter; instead, it
relies on the inherent inductance of the speaker coil and the
natural filtering capacity of the speaker and human ear to fully
recover the audio component of the square wave output.
The SSM2306 uses a proprietary modulation and spreadspectrum technology to minimize EMI emissions from the
device. Figure 34 shows SSM2306 EMI emission starting from
100 kHz to 30 MHz. Figure 35 shows SSM2306 EMI emission
from 30 kHz to 2 GHz. These figures clearly depict the SSM2306
EMI behavior as being well below the FCC regulation values,
starting from 100 kHz and passing beyond 1 GHz of frequency.
Although the overall EMI noise floor is slightly higher, frequency
spurs from the SSM2306 are greatly reduced.
70
60
= HORIZONTAL
= VERTICAL
= REGULATION VALUE
50
LEVEL (dB(µV/m))
Although most Class-D amplifiers use some variation of pulsewidth modulation (PWM), the SSM2306 uses sigma-delta (Σ-Δ)
modulation to determine the switching pattern of the output
devices. This provides 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 radiate by the use of speakers
and long cable traces. The SSM2306 also offers protection
circuits for overcurrent and overtemperature protection.
40
30
20
GAIN SELECTION
100
10k
Figure 34. EMI Emissions from SSM2306
70
60
= HORIZONTAL
= VERTICAL
= REGULATION VALUE
LEVEL (dB(µV/m))
50
Voltage transients at the output of audio amplifiers can occur with
the activation or deactivation of shutdown. Furthermore, voltage
transients as low as 10 mV are audible as an audio pop in the
speaker. Likewise, clicks and pops are classified as undesirable
audible transients generated by the amplifier system, and as
such, as not coming from the system input signal. These types
of transients generate when the amplifier system changes its
operating mode. For example, the following can be sources of
audible transients:
•
•
•
•
10
FREQUENCY (MHz)
External Gain Settings = 344 kΩ/(43 kΩ + REXT)
POP-AND-CLICK SUPPRESSION
1
06542-039
www.BDTIC.com/ADI
0
0.1
06542-040
10
The SSM2306 has a pair of internal resistors that set an 18 dB
default gain for the amplifier. It is possible to adjust the SSM2306
gain by using external resistors at the input. To set a gain lower
than 18 dB, refer to Figure 32 for the differential input configuration and Figure 33 for the single-ended configuration. Calculate
the external gain configuration as
40
30
20
10
0
10
100
1k
FREQUENCY (MHz)
Figure 35. EMI Emissions from SSM2306
System power-up/power-down
Mute/unmute
Input source change
Sample rate change
The SSM2306 has a pop-and-click suppression architecture that
reduces these output transients, resulting in noiseless activation and
deactivation.
The measurements for Figure 34 and Figure 35 were taken with
a 1 kHz input signal, producing 0.5 W output power into an 8 Ω
load from a 3.6 V supply. Cable length was approximately 5 cm.
To detect EMI, a magnetic probe was used touching the 2-inch
output trace to the load.
Rev. 0 | Page 12 of 16
SSM2306
LAYOUT
INPUT CAPACITOR SELECTION
As output power continues to increase, careful layout is needed
for proper placement of PCB traces and wires between the amplifier, load, and power supply. A good practice is to use short, wide
PCB tracks to decrease voltage drops and minimize inductance.
Make track widths at least 200 mil for every inch of track length
for lowest DCR, and use 1 oz. or 2 oz. of copper PCB traces to
further reduce IR drops and inductance. Poor layout increases
voltage drops, consequently affecting efficiency. Use large traces
for the power supply inputs and amplifier outputs to minimize
losses due to parasitic trace resistance. Proper grounding guidelines help to improve audio performance, minimize crosstalk
between channels, and prevent switching noise from coupling
into the audio signal.
The SSM2306 does not require input coupling capacitors if the
input signal is biased from 1.0 V to VDD − 1.0 V. Input capacitors
are required if the input signal is not biased within this recommended input dc common-mode voltage range, if high-pass
filtering is needed (see Figure 32), or if using a single-ended
source (see Figure 33). If high-pass filtering is needed at the
input, the input capacitor together with the input resistor of the
SSM2306 form a high-pass filter whose corner frequency is
determined by the following equation:
To maintain high output swing and high peak output power, the
PCB traces that connect the output pins to the load and supply
pins should be as wide as possible to maintain the minimum
trace resistances. It is also recommended to use a large area
ground plane for minimum impedances.
Good PCB layouts isolate critical analog paths from sources of
high interference; furthermore, separate high frequency circuits
(analog and digital) from low frequency ones. Properly designed
multilayer printed circuit boards can reduce EMI emission and
increase immunity to RF field by a factor of 10 or more compared
with double-sided boards. A multilayer board allows a complete
layer to be used for the ground plane, whereas the ground plane
side of a double-sided board is often disrupted with signal crossover. If the system has separate analog and digital ground and
power planes, the analog ground plane should be underneath
the analog power plane, and, similarly, the digital ground plane
should be underneath the digital power plane. There should be
no overlap between analog and digital ground planes or analog
and digital power planes.
fC = 1/(2π × RIN × CIN)
Input capacitors can have very important effects on the circuit
performance. Not using input capacitors degrades the output
offset of the amplifier as well as the PSRR performance.
PROPER POWER SUPPLY DECOUPLING
To ensure high efficiency, low total harmonic distortion (THD),
and high PSRR, proper power supply decoupling is necessary.
Noise transients on the power supply lines are short duration
voltage spikes. Although the actual switching frequency can
range from 10 kHz to 100 kHz, these spikes can contain frequency components that extend into the hundreds of megahertz.
The power supply input needs to be decoupled with a good
quality, low ESL and low ESR capacitor, usually around 4.7 μF.
This capacitor bypasses low frequency noises to the ground
plane. For high frequency transients noises, use a 0.1 μF capacitor
as close as possible to the VDD pin of the device. Placing the
decoupling capacitor as close as possible to the SSM2306 helps
maintain efficiency performance.
www.BDTIC.com/ADI
Rev. 0 | Page 13 of 16
SSM2306
OUTLINE DIMENSIONS
3.00
BSC SQ
0.60 MAX
0.45
PIN 1
INDICATOR
TOP
VIEW
13
12
2.75
BSC SQ
0.80 MAX
0.65 TYP
12° MAX
16
1
EXPOSED
PAD
0.50
BSC
0.90
0.85
0.80
0.50
0.40
0.30
PIN 1
INDICATOR
*1.65
1.50 SQ
1.35
9 (BOTTOM VIEW) 4
8
5
0.25 MIN
1.50 REF
0.05 MAX
0.02 NOM
SEATING
PLANE
0.30
0.23
0.18
0.20 REF
*COMPLIANT TO JEDEC STANDARDS MO-220-VEED-2
EXCEPT FOR EXPOSED PAD DIMENSION.
Figure 36. 16-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
3 mm × 3 mm Body, Very Thin Quad
(CP-16-3)
Dimensions shown in millimeters
ORDERING GUIDE
Model
SSM2306CPZ-R2 1
SSM2306CPZ-REEL1
SSM2306CPZ-REEL71
1
Temperature Range
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
Package Description
16-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
16-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
16-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
Package Option
CP-16-3
CP-16-3
CP-16-3
www.BDTIC.com/ADI
Z = RoHS Compliant Part.
Rev. 0 | Page 14 of 16
Branding
A1R
A1R
A1R
SSM2306
NOTES
www.BDTIC.com/ADI
Rev. 0 | Page 15 of 16
SSM2306
NOTES
www.BDTIC.com/ADI
©2007 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D06542-0-4/07(0)
Rev. 0 | Page 16 of 16