Datasheet ssm2356 Datasheet (ANALOG DEVICES)

2 × 2W Filterless Class-D

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
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

APPLICATIONS

Mobile phones
MP3 players
Portable gaming
Portable electronics

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 contin­uous output power with <1% THD + N driving a 4 Ω load from a

5.0 V supply.

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.

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.

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

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.

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 V
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.

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).

and

SDNR

/2. The preset gain of SSM2356 can be

DD

pins. The device also

SDNL

FUNCTIONAL BLOCK DIAGRAM

10µF

SSM2356

1

RIGHT IN+

RIGHT IN–

SHUTDOWN–R

SHUTDOWN–L

LEFT IN+

LEFT IN–

1

INPUT CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY V

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.

22nF

22nF

22nF

22nF

GAIN

80kΩ

INR+

INR–

80kΩ

1

SDNR

SDNL

1

80kΩ

INL+

INL–

80kΩ

1

GAIN

CONTROL

GAIN

CONTROL

GAIN

GAIN = 6dB OR 18dB

/2.

DD

VBATT

2.5V TO 5.5V

VDDVDD

FET

DRIVER

CONTROL

FET

DRIVER

GNDGND

EDGE

OUTR+

OUTR–

EDGE

OUTL+

OUTL–

EMISSION
CTRL

8084-001

MODULATOR

BIAS

BIAS

MODULATOR

0.1µF

(Σ-Δ)

INTERNAL

OSCILLATOR

(Σ-Δ)

Figure 1.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2009 Analog Devices, Inc. All rights reserved.

SSM2356

TABLE OF CONTENTS

Features .............................................................................................. 1

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

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

Rev. 0 | Page 2 of 16

SSM2356

SPECIFICATIONS

VDD = 5.0 V, TA = 25oC, RL = 8 Ω +33 H, EDGE = GND, Gain = 6 dB, unless otherwise noted.

Table 1.

Parameter Symbol Conditions Min Typ Max Unit

DEVICE CHARACTERISTICS

Output Power/Channel P

O

R

R

R

R

R

R

R

Efficiency η PO = 1.4 W, 8 Ω, VDD = 5.0 V, EDGE = GND

P

Total Harmonic Distortion + Noise THD + N PO = 1 W into 8 Ω, f = 1 kHz, VDD = 5.0 V 0.004 %

P

Input Common-Mode Voltage Range VCM 1.0 VDD − 1 V

Common-Mode Rejection Ratio CMRR

Channel Separation X

TAL K

Average Switching Frequency fSW 300 kHz

Differential Output Offset Voltage V

OOS

POWER SUPPLY

Supply Voltage Range V

Power Supply Rejection Ratio

DD

PSRR

(DC)
PSRR
Supply Current (stereo) I

SY

V
V

Shutdown Current ISD

GAIN CONTROL

Closed-Loop Gain Gain GAIN = VDD 18 dB
Gain GAIN = GND 6 dB
Input Impedance Z

IN

SHUTDOWN CONTROL

Input Voltage High V
Input Voltage Low V
Turn-On Time t

Turn-Off Time t
Output Impedance Z

IH

IL

WU

SD

OUT

NOISE PERFORMANCE

Output Voltage Noise en

Signal-to-Noise Ratio SNR PO = 1.4 W, RL = 8 Ω 100 dB

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.

RL = 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V 1.42 W

= 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V 0.75 W

L

= 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V 1.8 W

L

= 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V 0.94 W

L

= 4 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V 2.0 W

L

= 4 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V 1.3 W

L

= 4 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V

L

= 4 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V 1.7 W

L

2.5

1

92 %

(normal, low EMI mode)

= 1.4 W, 8 Ω, VDD = 5.0 V, EDGE = V

O

DD

90 %

(ultralow EMI mode)

= 0.5 W into 8 Ω, f = 1 kHz, VDD = 3.6 V 0.004 %

O

GSM VCM

= 2.5 V ± 100 mV at 217 Hz, output referred 55 dB

PO = 100 mW, f = 1 kHz 78 dB

Gain = 6 dB 2.0 mV

Guaranteed from PSRR test 2.5 5.5 V
VDD = 2.5 V to 5.0 V, dc input floating 70 85 dB

GSM VRIPPLE

= 100 mV at 217 Hz, inputs ac GND, CIN = 0.1 μF 60 dB

VIN = 0 V, no load, VDD = 5.0 V 5.75 mA

= 0 V, no load, VDD = 3.6 V 4.9 mA

IN

= 0 V, no load, VDD = 2.5 V 4.7 mA

IN

VIN = 0 V, load = 8 Ω+ 33 μH, VDD = 5.0 V
VIN = 0 V, load = 8 Ω+ 33 μH, VDD = 3.6 V

= 0 V, load = 8 Ω+ 33 μH, VDD = 2.5 V

V

IN

= SDNL= GND

SDNR

SDNR = SDNL = VDD; GAIN = GND or VDD

5.5 mA

5.1 mA

4.5 mA
20 nA

80 kΩ

1.35 V

0.35 V
SDNR/SDNL rising edge from GND to VDD
SDNR/SDNL falling edge from VDD to GND

/SDNL = GND

SDNR

= 3.6 V, f = 20 Hz to 20 kHz, inputs are ac grounded,

V

DD

7 ms
5 μs
>100 kΩ

29 μVrms

Gain = 6 dB, A-weighted

W

Rev. 0 | Page 3 of 16

SSM2356

ABSOLUTE MAXIMUM RATINGS

Absolute maximum ratings apply at 25°C, unless otherwise noted.

Table 2.

Parameter Rating

Supply Voltage 6 V
Input Voltage V
Common-Mode Input Voltage V
ESD Susceptibility 4 kV
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +85°C
Junction Temperature Range −65°C to +165°C
Lead Temperature Range

(Soldering, 60 sec)

DD

DD

300°C

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.

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. θ
according to JESD51-9 on a 4-layer printed circuit board (PCB)
with natural convection cooling.

Table 3. Thermal Resistance

Package Type θJA θJB Unit

16-ball, 1.66 mm × 1.66 mm WLCSP 66 19 °C/W

ESD CAUTION

and θJB (junction to board) are determined

JA

Rev. 0 | Page 4 of 16

SSM2356

PIN CONFIGURATION AND FUNCTION DESCRIPTIONS

BALL A1
INDICATOR

A

B

C

D

Figure 2. Pin Configuration (Top Side View)

Table 4. Pin Function Descriptions

Bump Mnemonic Description

A1 OUTL+ Noninverting Output for Left Channel.
B1 OUTL− Inverting Output for Left Channel.
C1

SDNL

Shutdown, Left Channel. Active low digital input.

D1 INL+ Noninverting Input for Left Channel.
D2 INL− Inverting Input for Left Channel.
C4

SDNR

Shutdown, Right Channel. Active low digital input.
C3 GAIN Gain select between 6 dB and 18 dB.
D3 INR− Inverting Input for Right Channel.
D4 INR+ Noninverting Input for Right Channel.

B2 GND Ground.
B4 OUTR− Inverting Output for Right Channel.

A4 OUTR+

Noninverting Output for Right Channel.
B3 GND Ground.
A2 VDD Power Supply.
A3 VDD Power Supply.
C2 EDGE Edge Control (Low Emission Mode); active high digital input.

234

1

OUTL+

VDD

OUTL–

GND

SDNL

EDGE

INL+

INL–

TOP VIEW

(BALL SIDE DO WN)

Not to Scal e

VDD

GND

GAIN

INR–

OUTR+

OUTR–

SDNR

INR+

08084-002

Rev. 0 | Page 5 of 16

SSM2356

TYPICAL PERFORMANCE CHARACTERISTICS

100

RL = 8Ω + 33µH
GAIN = 6dB

10

= 2.5V

V

DD

= 3.6V

V

DD

100

RL = 4Ω + 15µH
GAIN = 18dB

10

= 2.5V

V

DD

1

0.1

THD + N (%)

V

0.01

0.001

0.0001 0.001 0.01 0.1 1 10

OUTPUT POWER (W)

DD

Figure 3. THD + N vs. Output Power into 8 Ω, AV = 6 dB

100

RL = 8Ω + 33µH
GAIN = 18dB

= 2.5V

V

10

1

0.1

THD + N (%)

0.01

0.001

0.0001 0.001 0.01 0.1 1 10

OUTPUT POWER (W)

DD

= 3.6V

V

DD

V

DD

= 5V

= 5V

1

= 3.6V

V

0.1

THD + N (%)

0.01

0.001

0.0001 0.001 0.01 0.1 1 10

08084-101

OUTPUT POWER (W)

DD

V

= 5V

DD

08084-104

Figure 6. THD + N vs. Output Power into 4 Ω, AV = 18 dB

100

VDD = 5V
GAIN = 6dB

= 8Ω + 33µH

R

L

10

1

0.1

THD + N (%)

0.01

0.001

0.0001
10 100 1k 10k 100k

08084-102

0.25W

0.5W

FREQUENCY (Hz)

1W

08084-105

Figure 4. THD + N vs. Output Power into 8 Ω, A

100

RL = 4Ω + 15µH
GAIN = 6dB

= 2.5V

V

10

1

0.1

THD + N (%)

0.01

0.001

0.0001 0.001 0.01 0.1 1 10

OUTPUT POWER (W)

DD

= 3.6V

V

DD

= 18 dB

V

V

DD

Figure 5. THD + N vs. Output Power into 4 Ω, AV = 6 dB

= 5V

08084-103

Rev. 0 | Page 6 of 1

Figure 7. THD + N vs. Frequency, V

100

VDD = 5V
GAIN = 18d B

= 8Ω + 33µH

R

L

10

1

0.1

THD + N (%)

0.01

0.5W

0.001
10 100 1k 10k 100k

0.25W

FREQUENCY (Hz)

Figure 8. THD + N vs. Frequency, V

= 5 V, RL = 8 Ω, AV = 6 dB

DD

1W

= 5 V, RL = 8 Ω, AV = 18 dB

DD

6

08084-106

SSM2356

100

10

VDD = 5V
GAIN = 6dB

= 4Ω + 15µH

R

L

100

10

V

= 3.6V

DD

GAIN = 18d B

= 8Ω + 33µH

R

L

1

0.1

THD + N (%)

0.01

0.001
10 100 1k 10k 100k

FREQUENCY (Hz)

2W

0.5W

1W

Figure 9. THD + N vs. Frequency, VDD = 5 V, RL = 4 Ω, AV = 6 dB

100

VDD = 5V
GAIN = 18d B

= 4Ω + 15µH

R

L

10

1

2W

0.1

THD + N (%)

0.01

0.001
10 100 1k 10k 100k

0.5W

1W

FREQUENCY (Hz)

Figure 10. THD + N vs. Frequency, VDD = 5 V, RL = 8 Ω, AV = 18 dB

100

VDD = 3.6V
GAIN = 6dB

= 8Ω + 33µH

R

L

10

1

0.1

THD + N (%)

0.01

0.25W

0.001
10 100 1k 10k 100k

08084-107

Figure 12. THD + N vs. Frequency, V

100

VDD = 3.6V
GAIN = 6dB

= 4Ω + 15µH

R

L

10

1

0.1

THD + N (%)

0.01

0.001
10 100 1k 10k 100k

08084-108

0.25W

0.5W

0.125W

FREQUENCY (Hz)

= 3.6 V, RL = 8 Ω, AV = 18 dB

DD

1W

0.5W

FREQUENCY (Hz)

08084-110

08084-111

Figure 13. THD + N vs. Frequency, VDD = 3.6 V, RL = 4 Ω, AV = 6 dB

100

VDD = 3.6V
GAIN = 18d B

= 4Ω + 15µH

R

L

10

1

0.125W

0.5W

= 3.6 V, RL = 8 Ω, AV = 6 dB

DD

0.1

THD + N (%)

0.01

0.001

0.25W

10 100 1k 10k 100k

FREQUENCY (Hz)

Figure 11. THD + N vs. Frequency, V

08084-109

Rev. 0 | Page 7 of 1

1

0.1

THD + N (%)

0.01

0.001
10 100 1k 10k 100k

0.25W

0.5W

FREQUENCY (Hz)

Figure 14. THD + N vs. Frequency, V

1W

= 3.6 V, RL = 4 Ω, AV = 18 dB

DD

6

08084-112

SSM2356

100

VDD = 2.5V
GAIN = 6dB

= 8Ω + 33µH

R

L

10

100

10

V

= 2.5V

DD

GAIN = 18d B

= 4Ω + 15µH

R

L

0.5W

1

0.1

THD + N (%)

0.01

0.001

0.0625W

0.125W

10 100 1k 10k 100k

0.25W

FREQUENCY (Hz)

Figure 15. THD + N vs. Frequency, VDD = 2.5 V, RL = 8 Ω, AV = 6 dB

100

VDD = 2.5V
GAIN = 18d B

= 8Ω + 33µH

R

L

10

1

0.1

THD + N (%)

0.01

0.001

0.0625W

0.125W

10 100 1k 10k 100k

0.25W

FREQUENCY (Hz)

Figure 16. THD + N vs. Frequency, VDD = 2.5 V, RL = 8 Ω, AV = 18 dB

100

VDD = 2.5V
GAIN = 6dB

= 4Ω + 15µH

R

L

10

0.5W

1

0.1

THD + N (%)

0.25W

0.01

0.125W

0.001
10 100 1k 10k 100k

FREQUENCY (Hz)

Figure 17. THD + N vs. Frequency, V

= 2.5 V, RL = 4 Ω, AV = 6 dB

DD

1

0.1

THD + N (%)

0.01

0.001
10 100 1k 10k 100k

08084-113

1.25W

0.25W

FREQUENCY (Hz)

08084-116

Figure 18. THD + N vs. Frequency, VDD = 2.5 V, RL = 4 Ω, AV = 18 dB

7.0
ISY FOR BOTH CHANNEL S

GAIN = 6dB

6.5

6.0

5.5

5.0

SUPPLY CURRENT (mA)

4.5

4.0

2.5 3.0 3.5 4.0 4.5 5.0 5.5

08084-114

8Ω + 33µH

4Ω + 15µH

NO LOA D

SUPPLY VOLTAGE (V)

08084-117

Figure 19. Supply Current vs. Supply Voltage, AV = 6 dB

7.5
ISY FOR BOTH CHANNEL S

GAIN = 18d B

7.0

6.5

6.0

5.5

5.0

SUPPLY CURRENT (mA)

4.5

4.0

2.5 3.0 3.5 4.0 4.5 5.0 5.5

08084-115

8Ω + 33µH

Figure 20. Supply Current vs. Supply Voltage, A

4Ω + 15µH

NO LOAD

SUPPLY VOLTAGE (V)

= 18 dB

V

08084-118

Rev. 0 | Page 8 of 16

SSM2356

2.0
f = 1kHz

GAIN = 6dB

1.8

= 8Ω + 33µH

R

L

1.6

1.4

1.2

1.0

0.8

OUTPUT POWER (W)

0.6

0.4

0.2

0

2.53.03.54.04.55.0

10%

1%

SUPPLY VOLTAGE (V)

08084-119

Figure 21. Maximum Output Power vs. Supply Voltage, RL = 8 Ω, AV = 6 dB

1.8
f = 1kHz

GAIN = 18d B

1.6

= 8Ω + 33µH

R

L

1.4

1.2

1.0

0.8

0.6

OUTPUT POWER (W)

0.4

0.2

0

2.53.03.54.04.55.0

10%

1%

SUPPLY VOLTAGE (V)

08084-120

Figure 22. Maximum Output Power vs. Supply Voltage, RL = 8 Ω, AV = 18 dB

3.5
f = 1kHz

GAIN = 6dB

= 4Ω + 15µH

R

3.0

L

2.5

2.0

1.5

OUTPUT POWER (W)

1.0

0.5

0

2.53.03.54.04.55.0

Figure 23. Maximum Output Power vs. Supply Voltage, R

10%

1%

SUPPLY VOLTAGE (V)

= 4 Ω, AV = 6 dB

L

08084-121

3.5
f = 1kHz

GAIN = 18d B

= 4Ω + 15µH

R

3.0

L

2.5

2.0

1.5

OUTPUT POWER (W)

1.0

0.5

0

2.53.03.54.04.55.0

10%

SUPPLY VOLTAGE (V)

1%

08084-122

Figure 24. Maximum Output Power vs. Supply Voltage, RL = 4 Ω, AV = 18 dB

100

VDD = 2.5V

90

= 5V

= 3.6V

80

70

60

50

40

EFFICIE NCY (%)

30

20

10

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

V

DD

OUTPUT PO WER (W)

V

DD

GAIN = 6dB

= 8Ω + 33µH

R

L

FOR BOTH CHANNEL S

P

OUT

08084-123

Figure 25. Efficiency vs. Output Power into 8 Ω

100

90

80

= 3.6V

V

70

V

= 2.5V

DD

60

50

40

EFFICIE NCY (%)

30

20

10

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

DD

OUTPUT PO WER (W)

= 5V

V

DD

GAIN = 6dB

= 4Ω + 15µH

R

L

FOR BOTH CHANNEL S

P

OUT

08084-124

Figure 26. Efficiency vs. Output Power into 4 Ω

Rev. 0 | Page 9 of 16

SSM2356

0.8
GAIN = 6dB

= 8Ω + 33µH

R

L

0.7

, P

I

SY

0.6

0.5

0.4

VDD = 2.5V

0.3

SUPPLY CURRENT (A)

0.2

0.1

0

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Figure 27. Supply Current vs. Output Power into 8 Ω

1.6
GAIN = 6dB

R

= 4Ω + 15µH

L

1.4

, P

I

SY

1.2

1.0

0.8

V

DD

0.6

SUPPLY CURRENT (A)

0.4

0.2

0

0 1.0 2.0 3.0 4.0 5.0 6.0 6.50.5 1.5 2.5 3.5 4. 5 5.5

Figure 28. Supply Current vs. Output Power into 4 Ω

0

VDD = 5V
V

OUT

R

= 8Ω + 33µH

L

–20

–40

FOR BOTH CHANNEL S

OUT

V

DD

OUTPUT PO WER (W)

FOR BOTH CHANNEL S

OUT

V

DD

= 2.5V

OUTPUT PO WER (W)

= 500mV rms

= 3.6V

= 3.6V

0

V

= 5V

DD

08084-125

–10

–20

–30

–40

–50

CMRR (dB)

–60

–70

–80

–90

–100

10 1k 100k100 10k

FREQUENCY (Hz)

08084-129

Figure 30. CMRR vs. Frequency

0

V

= 5V

DD

08084-126

–10

–20

–30

–40

–50

PSRR (dB)

–60

–70

–80

–90

–100

10 1k 100k100 10k

FREQUENCY (Hz)

08084-130

Figure 31. PSRR vs. Frequency

6

5

4

3

SD INPUT

–60

–80

CHANNEL SEPARATIO N (dB)

–100

–120

1 10 100 1k 10k 100 k

FREQUENCY (Hz)

RIGHT TO LEFT

LEFT TO RIGHT

Figure 29. Crosstalk v. Frequency

08084-133

Rev. 0 | Page 10 of 16

2

VOLTAGE (V)

1

0

–1

–2

–2 181614121086420

OUTPUT

TIME (ms)

08084-131

Figure 32. Turn-On Response

SSM2356

7

6

5

4

3

2

VOLTAGE (V)

1

0

–1

–2

–110 –90 –70 –50 –30 –10 10 30 50 70

TIME (µs)

OUTPUT

SD INPUT

08084-132

Figure 33. Turn-Off Response

Rev. 0 | Page 11 of 16

SSM2356

TYPICAL APPLICATION CIRCUITS

SSM2356

R

EXT

INR+

INR–

R

EXT

SDNR

SDNL

R

EXT

INL+

INL–

R

EXT

GAIN

EXTERNAL G AIN SETT INGS = 160kΩ/(80kΩ + R

Figure 34. Stereo Differential Input Configuration

RIGHT AUDIO IN+

RIGHT AUDIO IN–

SHUTDOWN–R

SHUTDOWN–L

LEFT AUDIO IN+

LEFT AUDIO IN–

22nF

22nF

22nF

22nF

80kΩ

80kΩ

80kΩ

80kΩ

CONTROL

CONTROL

GAIN

GAIN

GAIN

10µF

0.1µF

MODULATOR

BIAS

BIAS

MODULATOR

= 640kΩ/(80kΩ + R

(Σ-Δ)

INTERNAL

OSCILLAT OR

(Σ-Δ)

) {GAIN = GND}

EXT

) {GAIN = VBATT }

EXT

VBATT

2.5V TO 5. 5V

VDDVDD

FET

DRIVER

CONTROL

FET

DRIVER

GNDGND

EDGE

OUTR+

OUTR–

EDGE

OUTL+

OUTL–

08084-003

RIGHT AUDIO IN+

SHUTDOWN–R

SHUTDOWN–L

LEFT AUDIO IN+

10µF

22nF

22nF

22nF

22nF

SSM2356

R

EXT

R

EXT

R

EXT

R

EXT

GAIN

EXTERNAL GAIN SETTINGS = 160kΩ/(80kΩ + R

INR+

INR–

SDNR

SDNL

INL+

INL–

80kΩ

80kΩ

80kΩ

80kΩ

CONTROL

CONTROL

GAIN

GAIN

GAIN

= 640kΩ/(80kΩ + R

Figure 35. Stereo Single-Ended Input Configuration

MODULATOR

BIAS

BIAS

MODULATOR

0.1µF

(Σ-Δ)

INTERNAL

OSCIL LATO R

(Σ-Δ)

) {GAIN = GND}

EXT

) {GAIN = VBATT}

EXT

VBATT

2.5V TO 5. 5V

VDDVDD

FET

DRIVER

CONTROL

FET

DRIVER

GNDGND

EDGE

OUTR+

OUTR–

EDGE

OUTL+

OUTL–

08084-004

Rev. 0 | Page 12 of 16

SSM2356

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- modulation to determine
the switching pattern of the output devices, resulting in a number
of important benefits. Σ- modulators do not produce a sharp
peak with many harmonics in the AM frequency band, as pulse­width modulators often do. Σ- 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- 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

), refer to Figure 34 for the differential input

DD

configuration and Figure 35 for the single-ended configuration.
Calculate the external gain configuration as follows:

When GAIN = GND

External Gain Settings = 160 kΩ/(80 kΩ + R

When GAIN = V

DD

External Gain Settings = 640 kΩ/(80 kΩ + R

EXT

EXT

)

)

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:

• System power-up/power-down

• Mute/unmute

• Input source change

• Sample rate change

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 spread­spectrum 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 per­formed in a certified FCC Class-B laboratory in normal
emissions mode (EDGE = GND). Figure 37 shows SSM2356
EMI emission with EDGE = V
emissions mode.

60

50

40

30

(dBµV)

20

10

0

30 130 230 330 430 530 630 730 830 930 1000

Figure 36. EMI Emissions from SSM2356, 1-Channel, 12 cm Cable,

60

50

40

30

(dBµV)

20

10

0

30 130 230 330 430 530 630 730 830 930 1000

Figure 37. EMI Emissions from SSM2356, 1-Channel, 12 cm Cable,

, placing the device in low

DD

[1] HORIZONTAL

[2] VERTICAL

FCC CLASS-B LI MIT

FREQUENCY (MHz)

EDGE = GND

[1] HORIZONTAL

[2] VERTICAL

FCC CLASS-B LI MIT

FREQUENCY (MHz)

EDGE = V

DD

08084-005

08084-006

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.

OUTPUT MODULATION DESCRIPTION

The SSM2356 uses three-level, Σ- output modulation. Each
output can swing from GND to V
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 differ­ential pulse is generated. However, most of the time, output
differential voltage is 0 V, due to the Analog Devices three-level,
Σ- output modulation. This feature ensures that the current
flowing through the inductive load is small.

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- output modulation with and without input
stimulus.

OUTPUT = 0V

OUT+

OUT–

VOUT

OUTPUT > 0V

OUT+

OUT–

VOUT

OUTPUT < 0V

OUT+

OUT–

VOUT

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

and vice versa. Ideally, when

DD

+5V

0V

+5V

0V
+5V

0V

–5V

+5V

0V

+5V

0V

+5V

0V

+5V

0V

+5V

0V

0V

–5V

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 inter­ference. High frequency circuits (analog and digital) should be
separated from low frequency circuits.

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.

INPUT CAPACITOR SELECTION

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 recom­mended input dc common-mode voltage range, if high-pass
filtering is needed, or if a single-ended source is used. If high­pass 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:

f

= 1/(2π × RIN × CIN)

C

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.

8084-007

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. 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 µF. This capacitor bypasses low freq­uency noises to the ground plane. For high frequency transient
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 SSM2356 helps to maintain efficient
performance.

Rev. 0 | Page 14 of 16

SSM2356

R

OUTLINE DIMENSIONS

0.660

0.600

0.540

SEATING
PLANE

0.290

0.260

0.230

1.20

BSC

3

2

4

1

A

B

C

BALL A1

IDENTIFIE

1.700

1.660 SQ

1.620

D

040209-B

TOP VIEW

(BALL SIDE DOWN )

0.430

0.400

0.370

0.07
COPLANARITY

0.230

0.200

0.170

0.40

BSC

BOTTOM VIEW

(BALL SIDE UP)

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 −40°C to +85°C 16-Ball Wafer Level Chip Scale Package [WLCSP] CB-16-4 Y1R
SSM2356CBZ-REEL71 −40°C to +85°C 16-Ball Wafer Level Chip Scale Package [WLCSP] CB-16-4 Y1R
EVAL-SSM2356Z1 Evaluation Board

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