EVAL-SSM2356Z [ADI]
2 × 2W Filterless Class-D Stereo Audio Amplifier; 2 × 2W无滤波器D类立体声音频放大器
| 型号： | EVAL-SSM2356Z |
| 厂家： | 
ADI |
| 描述： | 2 × 2W Filterless Class-D Stereo Audio Amplifier |
| 文件： | 总16页 (文件大小：634K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
2 × 2W Filterless Class-D
Stereo Audio Amplifier
SSM2356
The SSM2356 features a high efficiency, low noise modulation
scheme that requires no external LC output filters. The modulation
continues to provide high efficiency even at low output power.
It operates with 92% efficiency at 1.4 W into 8 Ω or 85% efficiency
at 2.0 W into 4 Ω from a 5.0 V supply and has an SNR of >103 dB.
FEATURES
Filterless stereo Class-D amplifier with Σ-Δ modulation
No sync necessary when using multiple Class-D amplifiers
from Analog Devices, Inc.
2 × 2W into 4 Ω load and 2x1.4 W into 8 Ω load at 5.0 V
supply with <1% total harmonic distortion (THD + N)
92% efficiency at 5.0 V, 1.4 W into 8 Ω speaker
>103 dB signal-to-noise ratio (SNR)
Single-supply operation from 2.5 V to 5.5 V
20 nA shutdown current; left/right channel control
Short-circuit and thermal protection
Spread-spectrum pulse density modulation is used to provide
lower EMI-radiated emissions compared with other Class-D
architectures. The SSM2356 includes an optional modulation
select pin (ultralow EMI emission mode) that significantly
reduces the radiated emissions at the Class-D outputs, particularly
above 100 MHz.
Available in a 16-ball, 1.66 mm × 1.66 mm WLCSP
Pop-and-click suppression
Built-in resistors that reduce board component count
User-selectable 6 dB or 18 dB gain setting
User-selectable ultralow EMI emission mode
The SSM2356 has a micropower shutdown mode with a typical
shutdown current of 20 nA. Shutdown is enabled by applying
a logic low to the
and
pins. The device also
SDNR
SDNL
includes pop-and-click suppression circuitry that minimizes
voltage glitches at the output during turn-on and turn-off,
reducing audible noise on activation and deactivation.
APPLICATIONS
Mobile phones
MP3 players
Portable gaming
Portable electronics
The fully differential input of the SSM2356 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. 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. Gain can be further
reduced to a user-defined setting by inserting series external
resistors at the inputs.
GENERAL DESCRIPTION
The SSM2356 is a fully integrated, high efficiency, stereo Class-D
audio amplifier. It is designed to maximize performance for
mobile phone applications. The application circuit requires
a minimum of external components and operates from a single
2.5 V to 5.5 V supply. It is capable of delivering 2 × 2W of contin-
uous output power with <1% THD + N driving a 4 Ω load from a
5.0 V supply.
The SSM2356 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-ball, 1.66 mm ×
1.66 mm wafer level chip scale package (WLCSP).
FUNCTIONAL BLOCK DIAGRAM
VBATT
2.5V TO 5.5V
10µF
0.1µF
VDD
VDD
SSM2356
1
1
22nF
22nF
80kΩ
OUTR+
RIGHT IN+
RIGHT IN–
GAIN
CONTROL
FET
DRIVER
MODULATOR
INR+
OUTR–
(Σ-Δ)
INR–
80kΩ
EMISSION
CTRL
BIAS
BIAS
SHUTDOWN–R
SHUTDOWN–L
EDGE
INTERNAL
OSCILLATOR
EDGE
SDNR
SDNL
CONTROL
1
1
22nF
22nF
80kΩ
80kΩ
OUTL+
OUTL–
LEFT IN+
LEFT IN–
GAIN
CONTROL
FET
DRIVER
MODULATOR
(Σ-Δ)
INL+
INL–
GAIN
GND
GND
GAIN
INPUT CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY V /2.
GAIN = 6dB OR 18dB
1
DD
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 registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2009 Analog Devices, Inc. All rights reserved.
SSM2356
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications Information.............................................................. 13
Overview ..................................................................................... 13
Gain Selection............................................................................. 13
Pop-and-Click Suppression ...................................................... 13
EMI Noise.................................................................................... 13
Output Modulation Description .............................................. 14
Layout .......................................................................................... 14
Input Capacitor Selection.......................................................... 14
Proper Power Supply Decoupling............................................ 14
Outline Dimensions....................................................................... 15
Ordering Guide .......................................................................... 15
Applications....................................................................................... 1
General Description......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
Thermal Resistance ...................................................................... 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics ............................................. 6
Typical Application Circuits.......................................................... 12
REVISION HISTORY
5/09—Revision 0: Initial Version
Rev. 0 | Page 2 of 16
SSM2356
SPECIFICATIONS
VDD = 5.0 V, TA = 25oC, RL = 8 Ω +33 μH, EDGE = GND, Gain = 6 dB, unless otherwise noted.
Table 1.
Parameter
Symbol Conditions
PO RL = 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 5.0V
Min Typ
Max
Unit
DEVICE CHARACTERISTICS
Output Power/Channel
1.42
0.75
1.8
0.94
2.0
1.3
2.51
1.7
92
W
W
W
W
W
W
W
W
%
RL = 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 3.6V
RL = 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 5.0V
RL = 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 3.6V
RL = 4 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 5.0V
RL = 4 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 3.6V
RL = 4 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 = 3.6V
PO = 1.4 W, 8 Ω, VDD = 5.0 V, EDGE = GND
(normal, low EMI mode)
Efficiency
η
PO = 1.4 W, 8 Ω, VDD = 5.0 V, EDGE = VDD
90
%
(ultralow EMI mode)
Total Harmonic Distortion + Noise
THD + N PO = 1 W into 8 Ω, f = 1 kHz, VDD = 5.0V
PO = 0.5 W into 8 Ω, f = 1 kHz, VDD = 3.6 V
0.004
0.004
%
%
Input Common-Mode Voltage Range VCM
1.0
55
VDD − 1
V
Common-Mode Rejection Ratio
Channel Separation
Average Switching Frequency
Differential Output Offset Voltage
POWER SUPPLY
CMRRGSM VCM = 2.5 V 100 mV at 217 Hz, output referred
XTALK
fSW
dB
dB
kHz
mV
PO = 100 mW, f = 1 kHz
78
300
2.0
VOOS
Gain = 6 dB
Supply Voltage Range
VDD
Guaranteed from PSRR test
2.5
5.5
V
Power Supply Rejection Ratio
PSRR
(DC)
V
DD = 2.5 V to 5.0 V, dc input floating
70
85
dB
PSRRGSM VRIPPLE = 100 mV at 217 Hz, inputs ac GND, CIN = 0.1 μF
60
dB
Supply Current (stereo)
ISY
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
5.75
4.9
4.7
5.5
5.1
4.5
20
mA
mA
mA
mA
mA
mA
nA
VIN = 0 V, load = 8 Ω + 33 μH, VDD = 5.0 V
VIN = 0 V, load = 8 Ω + 33 μH, VDD = 3.6 V
VIN = 0 V, load = 8 Ω + 33 μH, VDD = 2.5 V
SDNR = SDNL= GND
Shutdown Current
ISD
GAIN CONTROL
Closed-Loop Gain
Gain
Gain
ZIN
GAIN = VDD
GAIN = GND
SDNR = SDNL = VDD; GAIN = GND or VDD
18
6
80
dB
dB
kΩ
Input Impedance
SHUTDOWN CONTROL
Input Voltage High
Input Voltage Low
Turn-On Time
VIH
VIL
tWU
tSD
1.35
0.35
7
V
V
ms
μs
kΩ
SDNR/SDNL rising edge from GND to VDD
SDNR/SDNL falling edge from VDD to GND
SDNR/SDNL = GND
Turn-Off Time
5
Output Impedance
ZOUT
>100
NOISE PERFORMANCE
Output Voltage Noise
en
VDD = 3.6 V, f = 20 Hz to 20 kHz, inputs are ac grounded,
Gain = 6 dB, A-weighted
PO = 1.4 W, RL = 8 Ω
29
μVrms
dB
Signal-to-Noise Ratio
SNR
100
1 Note that, although the SSM2356 has good audio quality above 2 W per channel, continuous output power beyond 2 W per channel must be avoided due to device
packaging limitations.
Rev. 0 | Page 3 of 16
SSM2356
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings apply at 25°C, unless otherwise noted.
THERMAL RESISTANCE
θJA (junction to air) is specified for the worst-case conditions,
that is, a device soldered in a circuit board for surface-mount
packages. θJA and θJB (junction to board) are determined
according to JESD51-9 on a 4-layer printed circuit board (PCB)
with natural convection cooling.
Table 2.
Parameter
Rating
Supply Voltage
Input Voltage
6 V
VDD
VDD
4 kV
−65°C to +150°C
−40°C to +85°C
−65°C to +165°C
300°C
Common-Mode Input Voltage
ESD Susceptibility
Storage Temperature Range
Operating Temperature Range
Junction Temperature Range
Table 3. Thermal Resistance
Package Type
θJA
θJB
Unit
16-ball, 1.66 mm × 1.66 mm WLCSP
66
19
°C/W
Lead Temperature Range
(Soldering, 60 sec)
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.
Rev. 0 | Page 4 of 16
SSM2356
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
BALL A1
INDICATOR
1
2
3
4
OUTL+ VDD VDD OUTR+
OUTL– GND GND OUTR–
SDNL EDGE GAIN SDNR
INL+ INL– INR– INR+
A
B
C
D
TOP VIEW
(BALL SIDE DOWN)
Not to Scale
Figure 2. Pin Configuration (Top Side View)
Table 4. Pin Function Descriptions
Bump
Mnemonic
Description
A1
OUTL+
Noninverting Output for Left Channel.
Inverting Output for Left Channel.
B1
OUTL−
C1
SDNL
Shutdown, Left Channel. Active low digital input.
D1
D2
C4
C3
D3
D4
B2
B4
INL+
INL−
Noninverting Input for Left Channel.
Inverting Input for Left Channel.
Shutdown, Right Channel. Active low digital input.
Gain select between 6 dB and 18 dB.
Inverting Input for Right Channel.
Noninverting Input for Right Channel.
Ground.
SDNR
GAIN
INR−
INR+
GND
OUTR−
Inverting Output for Right Channel.
A4
B3
A2
A3
C2
OUTR+
GND
Noninverting Output for Right Channel.
Ground.
VDD
Power Supply.
VDD
Power Supply.
EDGE
Edge Control (Low Emission Mode); active high digital input.
Rev. 0 | Page 5 of 16
SSM2356
TYPICAL PERFORMANCE CHARACTERISTICS
100
100
10
R
= 8Ω + 33µH
R = 4Ω + 15µH
L
GAIN = 18dB
L
V
= 3.6V
DD
GAIN = 6dB
V
= 2.5V
V
= 2.5V
DD
DD
10
1
1
V
= 3.6V
DD
0.1
0.1
V
= 5V
DD
0.01
0.001
0.01
0.001
V
= 5V
DD
0.0001
0.001
0.01
0.1
1
10
0.0001
0.001
0.01
0.1
1
10
OUTPUT POWER (W)
OUTPUT POWER (W)
Figure 3. THD + N vs. Output Power into 8 Ω, AV = 6 dB
Figure 6. THD + N vs. Output Power into 4 Ω, AV = 18 dB
100
10
100
10
R
= 8Ω + 33µH
V
= 5V
L
DD
GAIN = 6dB
= 8Ω + 33µH
V
= 3.6V
DD
GAIN = 18dB
R
L
V
= 2.5V
DD
1
1
1W
0.1
0.25W
0.1
0.01
0.001
0.0001
V
= 5V
DD
0.01
0.001
0.5W
0.0001
0.001
0.01
0.1
1
10
10
100
1k
FREQUENCY (Hz)
10k
100k
OUTPUT POWER (W)
Figure 4. THD + N vs. Output Power into 8 Ω, AV = 18 dB
Figure 7. THD + N vs. Frequency, VDD = 5 V, RL = 8 Ω, AV = 6 dB
100
100
R
= 4Ω + 15µH
V
= 5V
L
DD
GAIN = 18dB
= 8Ω + 33µH
GAIN = 6dB
R
L
V
= 2.5V
DD
10
10
1
1
V
= 3.6V
1W
DD
0.1
0.1
0.01
0.001
0.01
0.001
0.25W
0.5W
V
= 5V
DD
0.0001
0.001
0.01
0.1
1
10
10
100
1k
FREQUENCY (Hz)
10k
100k
OUTPUT POWER (W)
Figure 5. THD + N vs. Output Power into 4 Ω, AV = 6 dB
Figure 8. THD + N vs. Frequency, VDD = 5 V, RL = 8 Ω, AV = 18 dB
Rev. 0 | Page 6 of 16
SSM2356
100
10
100
10
V
= 5V
V
= 3.6V
DD
GAIN = 6dB
= 4Ω + 15µH
DD
GAIN = 18dB
R
R
= 8Ω + 33µH
L
L
1
1
0.5W
2W
0.1
0.1
0.01
0.001
0.01
0.001
0.5W
0.125W
0.25W
1W
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 9. THD + N vs. Frequency, VDD = 5 V, RL = 4 Ω, AV = 6 dB
Figure 12. THD + N vs. Frequency, VDD = 3.6 V, RL = 8 Ω, AV = 18 dB
100
100
V
= 5V
V
= 3.6V
DD
GAIN = 18dB
= 4Ω + 15µH
DD
GAIN = 6dB
R
R
= 4Ω + 15µH
L
L
10
10
1
1
2W
1W
0.5W
0.1
0.1
0.25W
0.01
0.001
0.01
0.001
1W
0.5W
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
Figure 10. THD + N vs. Frequency, VDD = 5 V, RL = 8 Ω, AV = 18 dB
Figure 13. THD + N vs. Frequency, VDD = 3.6 V, RL = 4 Ω, AV = 6 dB
100
100
V
= 3.6V
V
= 3.6V
DD
GAIN = 6dB
DD
GAIN = 18dB
R
= 8Ω + 33µH
R
= 4Ω + 15µH
L
L
10
1
10
1
1W
0.5W
0.1
0.1
0.25W
0.125W
0.01
0.001
0.01
0.001
0.5W
0.25W
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
Figure 11. THD + N vs. Frequency, VDD = 3.6 V, RL = 8 Ω, AV = 6 dB
Figure 14. THD + N vs. Frequency, VDD = 3.6 V, RL = 4 Ω, AV = 18 dB
Rev. 0 | Page 7 of 16
SSM2356
100
100
10
V
= 2.5V
V
= 2.5V
DD
GAIN = 6dB
DD
GAIN = 18dB
R = 4Ω + 15µH
L
R
= 8Ω + 33µH
L
10
1
0.5W
1
0.25W
0.1
0.1
1.25W
0.0625W
0.01
0.001
0.01
0.001
0.25W
0.125W
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
Figure 15. THD + N vs. Frequency, VDD = 2.5 V, RL = 8 Ω, AV = 6 dB
Figure 18. THD + N vs. Frequency, VDD = 2.5 V, RL = 4 Ω, AV = 18 dB
100
7.0
V
= 2.5V
I
FOR BOTH CHANNELS
DD
GAIN = 18dB
SY
GAIN = 6dB
R
= 8Ω + 33µH
L
6.5
6.0
5.5
5.0
4.5
4.0
10
1
4Ω + 15µH
0.25W
8Ω + 33µH
0.1
0.0625W
NO LOAD
0.01
0.001
0.125W
10
100
1k
FREQUENCY (Hz)
10k
100k
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
Figure 16. THD + N vs. Frequency, VDD = 2.5 V, RL = 8 Ω, AV = 18 dB
Figure 19. Supply Current vs. Supply Voltage, AV = 6 dB
100
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
V
= 2.5V
I
FOR BOTH CHANNELS
DD
GAIN = 6dB
= 4Ω + 15µH
SY
GAIN = 18dB
R
L
10
1
0.5W
4Ω + 15µH
8Ω + 33µH
0.1
0.25W
NO LOAD
0.01
0.001
0.125W
10
100
1k
FREQUENCY (Hz)
10k
100k
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
Figure 17. THD + N vs. Frequency, VDD = 2.5 V, RL = 4 Ω, AV = 6 dB
Figure 20. Supply Current vs. Supply Voltage, AV = 18 dB
Rev. 0 | Page 8 of 16
SSM2356
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
f = 1kHz
GAIN = 6dB
f = 1kHz
GAIN = 18dB
R
= 8Ω + 33µH
R
= 4Ω + 15µH
L
L
10%
10%
1%
1%
2.5
3.0
3.5
4.0
4.5
5.0
2.5
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Figure 21. Maximum Output Power vs. Supply Voltage, RL = 8 Ω, AV = 6 dB
Figure 24. Maximum Output Power vs. Supply Voltage, RL = 4 Ω, AV = 18 dB
1.8
100
V
= 2.5V
f = 1kHz
DD
GAIN = 18dB
90
80
70
60
50
40
30
20
10
0
1.6
R
= 8Ω + 33µH
L
V = 5V
DD
V
= 3.6V
DD
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
10%
1%
GAIN = 6dB
R
= 8Ω + 33µH
L
P
FOR BOTH CHANNELS
OUT
2.5
3.0
3.5
4.0
4.5
5.0
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
OUTPUT POWER (W)
SUPPLY VOLTAGE (V)
Figure 22. Maximum Output Power vs. Supply Voltage, RL = 8 Ω, AV = 18 dB
Figure 25. Efficiency vs. Output Power into 8 Ω
3.5
100
90
80
70
60
50
40
30
20
10
0
f = 1kHz
GAIN = 6dB
R
= 4Ω + 15µH
3.0
2.5
2.0
1.5
1.0
0.5
0
L
V
= 5V
DD
V
= 3.6V
DD
V
= 2.5V
DD
10%
1%
GAIN = 6dB
R
= 4Ω + 15µH
L
P
FOR BOTH CHANNELS
OUT
2.5
3.0
3.5
4.0
4.5
5.0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
OUTPUT POWER (W)
SUPPLY VOLTAGE (V)
Figure 23. Maximum Output Power vs. Supply Voltage, RL = 4 Ω, AV = 6 dB
Figure 26. Efficiency vs. Output Power into 4 Ω
Rev. 0 | Page 9 of 16
SSM2356
0.8
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
GAIN = 6dB
= 8Ω + 33µH
V
= 5V
R
DD
L
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
I
, P FOR BOTH CHANNELS
SY OUT
V
= 3.6V
DD
V
= 2.5V
DD
0
0
1
0.5
1.0
1.5
2.0
2.5
3.0
3.5
10
100
1k
10k
100k
100k
18
OUTPUT POWER (W)
FREQUENCY (Hz)
Figure 27. Supply Current vs. Output Power into 8 Ω
Figure 30. CMRR vs. Frequency
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
GAIN = 6dB
= 4Ω + 15µH
V
= 5V
R
I
DD
L
, P FOR BOTH CHANNELS
SY OUT
V
= 3.6V
DD
V
= 2.5V
DD
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
OUTPUT POWER (W)
10
100
1k
10k
FREQUENCY (Hz)
Figure 28. Supply Current vs. Output Power into 4 Ω
Figure 31. PSRR vs. Frequency
0
–20
6
V
V
= 5V
= 500mV rms
= 8Ω + 33µH
DD
OUT
5
4
R
L
SD INPUT
–40
3
–60
2
OUTPUT
RIGHT TO LEFT
1
–80
0
–100
–120
–1
–2
LEFT TO RIGHT
10
100
1k
10k
100k
–2
0
2
4
6
8
10
12
14
16
FREQUENCY (Hz)
TIME (ms)
Figure 29. Crosstalk v. Frequency
Figure 32. Turn-On Response
Rev. 0 | Page 10 of 16
SSM2356
7
6
5
4
3
OUTPUT
2
1
0
–1
–2
SD INPUT
–110 –90
–70
–50
–30
–10
10
30
50
70
TIME (µs)
Figure 33. Turn-Off Response
Rev. 0 | Page 11 of 16
SSM2356
TYPICAL APPLICATION CIRCUITS
VBATT
2.5V TO 5.5V
10µF
0.1µF
VDD
VDD
SSM2356
22nF
22nF
R
80kΩ
EXT
EXT
OUTR+
RIGHT AUDIO IN+
RIGHT AUDIO IN–
GAIN
CONTROL
FET
DRIVER
MODULATOR
INR+
INR–
OUTR–
(Σ-Δ)
R
80kΩ
BIAS
BIAS
SHUTDOWN–R
SHUTDOWN–L
SDNR
SDNL
EDGE
INTERNAL
OSCILLATOR
EDGE
CONTROL
22nF
22nF
R
R
80kΩ
80kΩ
EXT
OUTL+
OUTL–
LEFT AUDIO IN+
LEFT AUDIO IN–
GAIN
CONTROL
FET
DRIVER
MODULATOR
(Σ-Δ)
INL+
INL–
EXT
GAIN
GND
GND
GAIN
EXTERNAL GAIN SETTINGS = 160kΩ/(80kΩ + R
= 640kΩ/(80kΩ + R
) {GAIN = GND}
) {GAIN = VBATT}
EXT
EXT
Figure 34. Stereo Differential Input Configuration
VBATT
2.5V TO 5.5V
10µF
0.1µF
VDD
VDD
SSM2356
22nF
22nF
R
R
80kΩ
EXT
EXT
OUTR+
RIGHT AUDIO IN+
SHUTDOWN–R
GAIN
FET
MODULATOR
INR+
OUTR–
CONTROL
DRIVER
(Σ-Δ)
INR–
80kΩ
BIAS
BIAS
SDNR
EDGE
INTERNAL
OSCILLATOR
EDGE
CONTROL
SHUTDOWN–L
SDNL
22nF
22nF
R
R
80kΩ
80kΩ
EXT
EXT
OUTL+
OUTL–
LEFT AUDIO IN+
GAIN
CONTROL
FET
DRIVER
MODULATOR
(Σ-Δ)
INL+
INL–
GAIN
GND
GND
GAIN
EXTERNAL GAIN SETTINGS = 160kΩ/(80kΩ + R
= 640kΩ/(80kΩ + R
) {GAIN = GND}
) {GAIN = VBATT}
EXT
EXT
Figure 35. Stereo Single-Ended Input Configuration
Rev. 0 | Page 12 of 16
SSM2356
APPLICATIONS INFORMATION
•
•
•
•
System power-up/power-down
Mute/unmute
Input source change
Sample rate change
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 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 = VDD, placing the device in low
emissions mode.
60
The SSM2356 also integrates overcurrent and temperature
protection.
50
40
30
20
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.
[1] HORIZONTAL
[2] VERTICAL
10
0
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 = VDD), refer to Figure 34 for the differential input
configuration and Figure 35 for the single-ended configuration.
Calculate the external gain configuration as follows:
FCC CLASS-B LIMIT
30
130 230 330 430 530 630 730 830 930 1000
FREQUENCY (MHz)
Figure 36. EMI Emissions from SSM2356, 1-Channel, 12 cm Cable,
EDGE = GND
When GAIN = GND
60
50
40
30
20
External Gain Settings = 160 kΩ/(80 kΩ + REXT
)
)
When GAIN = VDD
External Gain Settings = 640 kΩ/(80 kΩ + REXT
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.
10
[1] HORIZONTAL
[2] VERTICAL
FCC CLASS-B LIMIT
0
30
130 230 330 430 530 630 730 830 930 1000
FREQUENCY (MHz)
Such transients may be generated when the amplifier system
changes its operating mode. For example, the following can be
sources of audible transients:
Figure 37. EMI Emissions from SSM2356, 1-Channel, 12 cm Cable,
EDGE = VDD
Rev. 0 | Page 13 of 16
SSM2356
The measurements for Figure 36 and Figure 37 were taken in
an FCC-certified EMI laboratory with a 1 kHz input signal,
producing 0.5 W output power into an 8 Ω load from a 5 V
supply. Cable length was 12 cm, unshielded twisted pair
speaker cable. Note that reducing the supply voltage greatly
reduces radiated emissions.
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.
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 that a large ground
plane be used for minimum impedances. In addition, good PCB
layout isolates critical analog paths from sources of high inter-
ference. High frequency circuits (analog and digital) should be
separated from low frequency circuits.
OUTPUT MODULATION DESCRIPTION
The SSM2356 uses three-level, Σ-Δ output modulation. Each
output can swing from GND to VDD and vice versa. Ideally, when
no input signal is present, the output differential voltage is 0 V
because there is no need to generate a pulse. In a real-world
situation, there are always noise sources present.
Due to this constant presence of noise, a differential pulse is
generated, when required, in response to this stimulus. A small
amount of current flows into the inductive load when the differ-
ential pulse is generated. However, most of the time, output
differential voltage is 0 V, due to the Analog Devices three-level,
Σ-Δ output modulation. This feature ensures that the current
flowing through the inductive load is small.
Properly designed multilayer PCBs can reduce EMI emission
and increase immunity to the 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 by
signal crossover.
If the system has separate analog and digital ground and power
planes, the analog ground plane should be directly beneath the
analog power plane, and, similarly, the digital ground plane should
be directly beneath the digital power plane. There should be no
overlap between analog and digital ground planes or between
analog and digital power planes.
When the user wants to send an input signal, an output pulse is
generated to follow input voltage. The differential pulse density
is increased by raising the input signal level. Figure 38 depicts
three-level, Σ-Δ output modulation with and without input
stimulus.
OUTPUT = 0V
+5V
OUT+
INPUT CAPACITOR SELECTION
0V
+5V
The SSM2356 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 recom-
mended input dc common-mode voltage range, if high-pass
filtering is needed, or if a single-ended source is used. If high-
pass filtering is needed at the input, the input capacitor and the
input resistor of the SSM2356 form a high-pass filter whose
corner frequency is determined by the following equation:
OUT–
0V
+5V
VOUT
0V
–5V
OUTPUT > 0V
+5V
OUT+
OUT–
VOUT
0V
+5V
0V
+5V
0V
fC = 1/(2π × RIN × CIN)
OUTPUT < 0V
The input capacitor can significantly affect the performance of
the circuit. Not using input capacitors degrades both the output
offset of the amplifier and the dc PSRR performance.
+5V
OUT+
OUT–
VOUT
0V
+5V
0V
0V
PROPER POWER SUPPLY DECOUPLING
–5V
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. These spikes can contain frequency components
that extend into the hundreds of megahertz. The power supply
input must be decoupled with a good quality, low ESL, low ESR
capacitor, greater than 4.7 ꢀF. This capacitor bypasses low freq-
uency noises to the ground plane. For high frequency transient
noises, use a 0.1 ꢀF capacitor as close as possible to the VDD
pin of the device. Placing the decoupling capacitor as close as
possible to the SSM2356 helps to maintain efficient
Figure 38. Three-Level, Σ-Δ Output Modulation With and
Without Input Stimulus
LAYOUT
As output power continues to increase, care must be taken to
lay out PCB traces and wires properly among the amplifier,
load, and power supply. A good practice is to use short, wide
PCB tracks to decrease voltage drops and minimize inductance.
Ensure that track widths are at least 200 mil for every inch of
track length for the lowest dc resistance (DCR), and use 1 oz. or
2 oz. copper PCB traces to further reduce IR drops and
inductance. A poor layout increases voltage drops, consequently
performance.
Rev. 0 | Page 14 of 16
SSM2356
OUTLINE DIMENSIONS
0.660
0.600
0.540
1.700
1.660 SQ
1.620
SEATING
PLANE
4
3
2
1
A
BALL A1
IDENTIFIER
1.20
BSC
B
C
D
0.290
0.260
0.230
0.40
BSC
0.07
0.430
0.400
0.370
TOP VIEW
(BALL SIDE DOWN)
BOTTOM VIEW
(BALL SIDE UP)
COPLANARITY
0.230
0.200
0.170
Figure 4. 16-Ball Wafer Level Chip Scale Package [WLCSP]
(CB-16-4)
Dimensions shown in millimeters
ORDERING GUIDE
Model
Temperature Range Package Description
Package Option Branding
SSM2356CBZ-REEL1
SSM2356CBZ-REEL71
EVAL-SSM2356Z1
−40°C to +85°C
−40°C to +85°C
16-Ball Wafer Level Chip Scale Package [WLCSP]
16-Ball Wafer Level Chip Scale Package [WLCSP]
Evaluation Board
CB-16-4
CB-16-4
Y1R
Y1R
1 Z = RoHS Compliant Part.
Rev. 0 | Page 15 of 16
SSM2356
NOTES
©2009 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D08084-0-5/09(0)
Rev. 0 | Page 16 of 16
相关型号：
EVAL-SSM2377Z
Filterless, High Efficiency, Mono 2.5 W Class-D Audio Amplifier Pop-and-click suppression
ADI
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