Filterless, High Efficiency,
Mono 3 W Class-D Audio Amplifier
SSM2319
The SSM2319 features a high efficiency, low noise modulation
scheme that does not require any external LC output filters. The
modulation continues to provide high efficiency even at low output
power. It operates with 90% efficiency at 1.4 W into 8 Ω or 85%
efficiency at 3 W into 3 Ω from a 5.0 V supply and has an SNR
of 98 dB. Spread-spectrum pulse density modulation is used to
provide lower EMI-radiated emissions compared with other
Class-D architectures.
FEATURES
Filterless Class-D amplifier with ultraefficient spreadspectrum Σ-Δ modulation
Internal modulator synchronization (SYNC)
3 W into 3 Ω load and 1.4 W into 8 Ω load at 5.0 V supply
with <1% total harmonic distortion (THD)
90% efficiency at 5.0 V, 1.4 W into 8 Ω speaker
Signal-to-noise ratio (SNR): 98 dB
Single-supply operation: 2.5 V to 5.5 V
Ultralow shutdown current: 20 nA
Short-circuit and thermal protection with autorecovery
Available in 9-ball, 1.5 mm × 1.5 mm WLCSP
Pop-and-click suppression
Built-in resistors reduce board component count
Default fixed 12 dB or user-adjustable gain setting
SYNC can be activated in the event that end users are concerned
about clock intermodulation (beating effect) of several amplifiers in
close proximity.
The SSM2319 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.
APPLICATIONS
The device also includes pop-and-click suppression circuitry.
This minimizes voltage glitches at the output during turn-on and
turn-off, reducing audible noise on activation and deactivation.
Mobile phones
MP3 players
Portable gaming
Portable electronics
Educational toys
The default gain of the SSM2319 is 12 dB, but users can reduce
the gain by using a pair of external resistors (see the Gain section).
The SSM2319 is specified over the industrial temperature range
of −40°C to +85°C. It has built-in thermal shutdown and output
short-circuit protection. It is available in a 9-ball, 1.5 mm × 1.5 mm
wafer level chip scale package (WLCSP).
GENERAL DESCRIPTION
The SSM2319 is a fully integrated, high efficiency 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 3 W of continuous
output power with <1% THD + N driving a 3 Ω load from a
5.0 V supply.
FUNCTIONAL BLOCK DIAGRAM
0.1µF
10µF
SSM2319
0.1µF*
AUDIO IN–
AUDIO IN+
IN–
40kΩ
IN+
40kΩ
VBATT
2.5V TO 5.5V
VDD
160kΩ
OUT+
MODULATOR
(Σ-Δ)
FET
DRIVER
OUT–
0.1µF*
160kΩ
SHUTDOWN
SD
BIAS
POP/CLICK
SUPPRESSION
INTERNAL
OSCILLATOR
SYNC
SYNCO
SYNC OUTPUT
SYNC INPUT
*INPUT CAPACITORS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY VDD/2.
07550-001
GND SYNCI
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
©2008 Analog Devices, Inc. All rights reserved.
SSM2319
TABLE OF CONTENTS
Features .............................................................................................. 1
Theory of Operation ...................................................................... 14
Applications ....................................................................................... 1
Overview ..................................................................................... 14
General Description ......................................................................... 1
Gain .............................................................................................. 14
Functional Block Diagram .............................................................. 1
Pop-and-Click Suppression ...................................................... 14
Revision History ............................................................................... 2
Output Modulation Description .............................................. 14
Specifications..................................................................................... 3
Layout .......................................................................................... 15
Absolute Maximum Ratings............................................................ 5
Input Capacitor Selection .......................................................... 15
Thermal Resistance ...................................................................... 5
Power Supply Decoupling ......................................................... 15
ESD Caution .................................................................................. 5
Syncronization (SYNC) Operation .......................................... 15
Pin Configuration and Function Descriptions ............................. 6
Outline Dimensions ....................................................................... 17
Typical Performance Characteristics ............................................. 7
Ordering Guide .......................................................................... 17
Typical Application Circuits.......................................................... 12
REVISION HISTORY
8/08—Revision 0: Initial Version
Rev. 0 | Page 2 of 20
SSM2319
SPECIFICATIONS
VDD = 5.0 V, TA = 25oC, RL = 8 Ω +33 μH, SYNCI = GND (standalone mode), unless otherwise noted.
Table 1.
Parameter
DEVICE CHARACTERISTICS
Output Power
Symbol
Conditions
POUT
RL = 8 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 = 3.6 V
RL = 8 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
RL = 8 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 = 3.6 V
RL = 8 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
RL = 4 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 = 4 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 = 4 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 = 3 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V
RL = 3 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V
RL = 3 Ω, THD = 1%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
RL = 3 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 5.0 V
RL = 3 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 3.6 V
RL = 3 Ω, THD = 10%, f = 1 kHz, 20 kHz BW, VDD = 2.5 V
POUT = 1.4 W, 8 Ω, VDD = 5.0 V
POUT = 1 W into 8 Ω, f = 1 kHz, VDD = 5.0 V
POUT = 0.5 W into 8 Ω, f = 1 kHz, VDD = 3.6 V
Efficiency
Total Harmonic Distortion + Noise
η
THD + N
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
Average Switching Frequency
Differential Output Offset Voltage
POWER SUPPLY
Supply Voltage Range
Power Supply Rejection Ratio
VCM
CMRRGSM
fSW
VOOS
Supply Current
VDD
PSRR
PSRRGSM
ISY
Shutdown Current
Min
Typ
Max
1.41
0.72
0.33
1.77
0.91
0.42
2.53
1.28
0.56
3.17 1
1.6
0.72
3.11
1.52
0.68
3.71
1.9
0.85
93
0.06
0.02
1.0
VCM = 2.5 V ± 100 mV at 217 Hz, output referred
VDD − 1
57
300
2.0
G = 12 dB
5.5
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
%
%
%
V
dB
kHz
mV
ISD
Guaranteed from PSRR test
VDD = 2.5 V to 5.0 V, dc input floating/ground
VRIPPLE = 100 mV at 217 Hz, inputs ac GND, CIN = 0.1 μF
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
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
SD = GND
GAIN CONTROL
Closed-Loop Gain
Differential Input Impedance
Av
ZIN
SD = VDD
12
40
dB
kΩ
SHUTDOWN CONTROL
Input Voltage High
Input Voltage Low
Turn-On Time
Turn-Off Time
Output Impedance
VIH
VIL
tWU
tSD
ZOUT
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
28
5
>100
V
V
ms
μs
kΩ
Rev. 0 | Page 3 of 20
2.5
70
Unit
85
60
3.6
3.2
2.7
3.7
3.3
2.8
20
V
dB
dB
mA
mA
mA
mA
mA
mA
nA
SSM2319
Parameter
NOISE PERFORMANCE
Output Voltage Noise
Symbol
Conditions
en
Signal-to-Noise Ratio
SYNC OPERATIONAL FREQUENCY
SNR
VDD = 3.6 V, f = 20 Hz to 20 kHz, inputs are ac grounded,
AV = 12 dB, A weighting
POUT = 1.4 W, RL = 8 Ω
1
Min
5
Typ
Max
40
μV
98
dB
MHz
12
Although the SSM2319 has good audio quality above 3 W, continuous output power beyond 3 W must be avoided due to device packaging limitations.
Rev. 0 | Page 4 of 20
Unit
SSM2319
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
Storage Temperature Range
Operating Temperature Range
Junction Temperature Range
Lead Temperature (Soldering, 60 sec)
ESD Susceptibility
Rating
6V
VDD
VDD
−65°C to +150°C
−40°C to +85°C
−65°C to +165°C
300°C
4 kV
Table 3.
Package Type
9-Ball, 1.5 mm × 1.5 mm WLCSP
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 5 of 20
PCB
1S0P
2S0P
θJA
162
76
θJB
39
21
Unit
°C/W
°C/W
SSM2319
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
BALL A1
CORNER
1
2
3
A
B
C
07550-002
SSM2319
TOP VIEW
BALL SIDE DOWN
(Not to Scale)
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No.
Mnemonic
Description
1A
1B
1C
2A
2B
2C
3A
3B
3C
IN−
IN+
GND
SD
Inverting Input.
Noninverting Input.
Ground.
Shutdown Input. Active low digital input.
SYNC Input.
Power Supply.
SYNC Output.
Inverting Output.
Noninverting Output.
SYNCI
VDD
SYNCO
OUT−
OUT+
Rev. 0 | Page 6 of 20
SSM2319
TYPICAL PERFORMANCE CHARACTERISTICS
100
RL = 8Ω + 33µH
GAIN = 12dB
1
THD + N (%)
0.1
0.001
0.01
0.1
1
10
OUTPUT POWER (W)
0.001
07550-003
0.001
0.0001
100
VDD = 2.5V
VDD = 3.6V
VDD = 5V
10k
100k
RL = 4Ω + 33µH
GAIN = 12dB
VDD = 5V
2W
1
THD + N (%)
THD + N (%)
1k
10
0.1
0.01
1
0.1
1W
0.5W
0.01
0.001
0.01
0.1
1
10
OUTPUT POWER (W)
0.001
07550-004
0.001
0.0001
10
1k
10k
100k
Figure 7. THD + N vs. Frequency, RL = 4 Ω + 33 μH, Gain = 12 dB, VDD = 5 V
100
RL = 3Ω + 33µH
GAIN = 12dB
VDD = 2.5V
VDD = 3.6V
VDD = 5V
RL = 3Ω + 33µH
GAIN = 12dB
VDD = 5V
10
THD + N (%)
10
100
FREQUENCY (Hz)
Figure 4. THD + N vs. Output Power into RL = 4 Ω + 33 μH, Gain = 12 dB
THD + N (%)
100
Figure 6. THD + N vs. Frequency, RL = 8 Ω + 33 μH, Gain = 12 dB, VDD = 5 V
RL = 4Ω + 33µH
GAIN = 12dB
10
10
FREQUENCY (Hz)
Figure 3. THD + N vs. Output Power into RL = 8 Ω + 33 μH, Gain = 12 dB
100
1W
0.5W
0.25W
0.1
0.01
0.01
100
1
07550-006
THD + N (%)
10
VDD = 2.5V
VDD = 3.6V
VDD = 5V
10
RL = 8Ω + 33µH
GAIN = 12dB
VDD = 5V
07550-007
100
1
3W
1
1.5W
0.75W
0.1
0.1
0.001
0.01
0.1
OUTPUT POWER (W)
1
10
0.001
07550-005
0.01
0.0001
10
100
1k
FREQUENCY (Hz)
Figure 5. THD + N vs. Output Power into RL = 3 Ω + 33 μH, Gain = 12 dB
10k
100k
07550-008
0.01
Figure 8. THD + N vs. Frequency, RL = 3Ω + 33 μH, Gain = 12 dB, VDD = 5 V
Rev. 0 | Page 7 of 20
SSM2319
100
RL = 8Ω + 33µH
GAIN = 12dB
VDD = 3.6V
RL = 8Ω + 33µH
GAIN = 12dB
VDD = 2.5V
10
10
1
1
THD + N (%)
0.1
0.1
0.5W
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 9. THD + N vs. Frequency, RL = 8 Ω + 33 μH, Gain = 12 dB, VDD = 3.6 V
100
0.001
07550-009
10
100
100
RL = 4Ω + 33µH
GAIN = 12dB
VDD = 2.5V
THD + N (%)
1W
0.5W
1
0.1
0.25W
0.125W
0.5W
0.25W
0.01
0.01
100
1k
10k
100k
Figure 10. THD + N vs. Frequency, RL = 4 Ω + 33 μH, Gain = 12 dB, VDD = 3.6 V
100
0.001
07550-010
10
FREQUENCY (Hz)
100
1k
10k
100k
Figure 13. THD + N vs. Frequency, RL = 4 Ω + 33 μH, Gain = 12 dB, VDD = 2.5 V
100
RL = 3Ω + 33µH
GAIN = 12dB
VDD = 2.5V
0.75W
10
1.5W
THD + N (%)
1
0.1
10
FREQUENCY (Hz)
RL = 3Ω + 33µH
GAIN = 12dB
VDD = 3.6V
10
THD + N (%)
100k
10
0.1
0.75W
0.38W
1
0.38W
0.2W
0.1
0.01
0.01
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
07550-011
0.001
10k
Figure 12. THD + N vs. Frequency, RL = 8 Ω + 33 μH, Gain = 12 dB, VDD = 2.5 V
RL = 4Ω + 33µH
GAIN = 12dB
VDD = 3.6V
1
0.001
1k
FREQUENCY (Hz)
10
THD + N (%)
0.125W
0.0625W
07550-013
0.001
0.01
0.25W
0.125W
07550-012
0.01
0.25W
Figure 11. THD + N vs. Frequency, RL = 3 Ω + 33 μH, Gain = 12 dB, VDD = 3.6 V
10
100
1k
FREQUENCY (Hz)
10k
100k
07550-014
THD + N (%)
100
Figure 14. THD + N vs. Frequency, RL = 3 Ω + 33 μH, Gain = 12 dB, VDD = 2.5 V
Rev. 0 | Page 8 of 20
SSM2319
2.0
3.7
RL = 8Ω + 33µH
RL = 8Ω + 33µH
GAIN = 12dB
f = 1kHz
1.8
3.5
3.3
3.1
OUTPUT POWER (W)
SUPPLY CURRENT (mA)
1.6
RL = 4Ω + 33µH
2.9
RL = 3Ω + 33µH
2.7
NO LOAD
1.4
1.2
10%
1.0
0.8
1%
0.6
0.4
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
0
2.5
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
Figure 15. Supply Current vs. Supply Voltage
Figure 18. Maximum Output Power vs. Supply Voltage,
RL = 8 Ω + 33 μH, Gain = 12 dB
4.0
100
VDD = 2.5V
90
3.5
DO NOT EXCEED 3W
CONTINUOUS OUTPUT POWER
3.0
VDD = 5V
80
70
EFFICIENCY (%)
OUTPUT POWER (W)
3.0
07550-018
0.2
07550-015
2.3
2.5
2.5
10%
2.0
1.5
1%
VDD = 3.6V
60
50
40
30
1.0
20
RL = 3Ω + 33µH
GAIN = 12dB
f = 1kHz
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
0
RL = 8Ω + 33µH
0
0.2
0.4
0.6
0.8
1.2
1.4
1.6
1.8
2.0
OUTPUT POWER (W)
Figure 19. Efficiency vs. Output Power into RL = 8 Ω + 33 μH
Figure 16. Maximum Output Power vs. Supply Voltage,
RL = 3 Ω + 33 μH, Gain = 12 dB
100
3.5
DO NOT EXCEED 3W
CONTINUOUS OUTPUT POWER
90
3.0
80
2.5
VDD = 2.5V
VDD = 3.6V
VDD = 5V
2.0
EFFICIENCY (%)
70
10%
1.5
1%
1.0
60
50
40
30
20
0
2.5
RL = 4Ω + 33µH
GAIN = 12dB
f = 1kHz
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
10
0
RL = 4Ω + 33µH
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
OUTPUT POWER (W)
Figure 20. Efficiency vs. Output Power into RL = 4 Ω + 33 μH
Figure 17. Maximum Output Power vs. Supply Voltage,
RL = 4 Ω + 33 μH, Gain = 12 dB
Rev. 0 | Page 9 of 20
07550-020
0.5
07550-017
OUTPUT POWER (W)
1.0
07550-019
0
2.5
10
07550-016
0.5
SSM2319
100
0.9
90
0.8
VDD = 3.6V
VDD = 5V
VDD = 2.5V
60
50
40
30
20
0
450
RL = 8Ω + 33µH
0.5
1.0
1.5
2.0
2.5
3.0
3.5
RL = 8Ω + 33µH
400
VDD = 5V
350
0.12
SUPPLY CURRENT (mA)
VDD = 5V
0.10
0.08
0.06
VDD = 3.6V
0.04
300
VDD = 3.6V
250
VDD = 2.5V
200
150
100
VDD = 2.5V
50
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
OUTPUT POWER (W)
0
07550-022
0
0.5
1.0
1.5
2.0
2.5
OUTPUT POWER (W)
Figure 22. Power Dissipation vs. Output Power into RL = 8 Ω + 33 μH
0.30
0
07550-025
POWER DISSIPATION (W)
0.2
Figure 24. Power Dissipation vs. Output Power into RL = 3 Ω + 33 μH
0.02
Figure 25. Supply Current vs. Output Power into RL = 8 Ω + 33 μH
800
RL = 4Ω + 33µH
RL = 4Ω + 33µH
700
0.25
VDD = 5V
VDD = 5V
SUPPLY CURRENT (mA)
POWER DISSIPATION (W)
VDD = 2.5V
0.3
OUTPUT POWER (W)
0.14
0.20
VDD = 3.6V
0.15
VDD = 2.5V
0.10
0.05
600
VDD = 3.6V
500
400
VDD = 2.5V
300
200
100
0
0.5
1.0
1.5
2.0
OUTPUT POWER (W)
2.5
3.0
07550-023
0
0.4
0
07550-021
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
Figure 21. Efficiency vs. Output Power into RL = 3 Ω + 33 μH
0
VDD = 3.6V
0.5
07550-024
RL = 3Ω + 33µH
OUTPUT POWER (W)
0.16
0.6
0.1
10
0
VDD = 5V
0.7
Figure 23. Power Dissipation vs. Output Power into RL = 4 Ω + 33 μH
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
OUTPUT POWER (W)
Figure 26. Supply Current vs. Output Power into RL = 4 Ω + 33 μH
Rev. 0 | Page 10 of 20
07550-026
EFFICIENCY (%)
70
POWER DISSIPATION (W)
80
RL = 3Ω + 33µH
SSM2319
7
RL = 3Ω + 33µH
800
VDD = 5V
5
VDD = 3.6V
VDD = 2.5V
3
2
300
1
200
0
100
–1
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
OUTPUT POWER (W)
–2
–10 –5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
TIME (ms)
Figure 27. Supply Current vs. Output Power into RL = 3 Ω + 33 μH
Figure 30. Turn-On Response
0
7
–10
6
–20
VOLTAGE (V)
PSRR (dB)
4
–40
–50
–60
2
0
–90
–1
100
1k
10k
100k
07550-028
–80
FREQUENCY (Hz)
Figure 28. Power Supply Rejection Ratio (PSRR) vs. Frequency
–10
–20
–30
–40
–50
–60
–70
–80
1k
10k
100k
FREQUENCY (Hz)
07550-029
–90
100
–2
–100
SD INPUT
–80
–60
–40
–20
0
20
40
TIME (µs)
Figure 31. Turn-Off Response
0
CMRR (dB)
3
1
–70
–100
10
OUTPUT
5
–30
–100
10
07550-030
VOLTAGE (V)
500
400
SD INPUT
4
07550-027
SUPPLY CURRENT (mA)
700
600
OUTPUT
6
Figure 29. Common-Mode Rejection Ratio (CMRR) vs. Frequency
Rev. 0 | Page 11 of 20
60
80
100
07550-031
900
SSM2319
TYPICAL APPLICATION CIRCUITS
EXTERNAL GAIN SETTINGS = 160kΩ/(40kΩ + REXT)
0.1µF
10µF
SSM2319
0.1µF*
AUDIO IN–
REXT
REXT
AUDIO IN+
IN–
IN+
VBATT
2.5V TO 5.5V
VDD
160kΩ
40kΩ
40kΩ
OUT+
MODULATOR
(Σ-Δ)
FET
DRIVER
OUT–
0.1µF*
160kΩ
SD
SHUTDOWN
POP/CLICK
SUPPRESSION
INTERNAL
OSCILLATOR
BIAS
SYNC
SYNC OUTPUT
SYNCO
GND SYNCI
07550-032
SYNC INPUT
*INPUT CAPACITORS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY VDD/2.
Figure 32. Differential Input Configuration, User-Adjustable Gain
EXTERNAL GAIN SETTINGS = 160kΩ/(40kΩ + REXT )
0.1µF
10µF
SSM2319
0.1µF
REXT
REXT
AUDIO IN+
IN–
IN+
VBATT
2.5V TO 5.5V
VDD
160kΩ
40kΩ
40kΩ
OUT+
MODULATOR
(Σ-Δ)
FET
DRIVER
OUT–
0.1µF
160kΩ
BIAS
POP/CLICK
SUPPRESSION
INTERNAL
OSCILLATOR
GND
SYNC
SYNCO
SYNC OUTPUT
SYNCI
SYNC INPUT
Figure 33. Single-Ended Input Configuration, User-Adjustable Gain
Rev. 0 | Page 12 of 20
07550-033
SHUTDOWN
SD
SSM2319
SSM2319
SSM2319
SSM2319
STANDALONE
MASTER
SLAVE
INTERNAL
OSCILLATOR
FET
DRIVER
SYNC
OUT+
MODULATOR
(Σ-Δ)
OUT–
SYNC
OUTPUT
INTERNAL
OSCILLATOR
SYNCO
FET
DRIVER
SYNC
OUT+
MODULATOR
(Σ-Δ)
OUT–
SYNC
OUTPUT
FET
DRIVER
INTERNAL
OSCILLATOR
SYNC
SYNCO
SYNCI
SYNCI
SYNCI
SYNC
INPUT
SYNC
INPUT
SYNC
INPUT
TO SLAVE
OUT–
SYNC
OUTPUT
SYNCO
07550-035
OUT+
MODULATOR
(Σ-Δ)
FROM MASTER
NOTES
1. TRACE LENGTH FROM SYNCI TO SYNCO IS LESS THAN 1mm.
Figure 34. Synchronization Operation Modes
SSM2319
MASTER
SLAVE 1
SSM2319
SLAVE 2
OUT+
MODULATOR
(Σ-Δ)
INTERNAL
OSCILLATOR
FET
DRIVER
SYNC
OUT+
MODULATOR
(Σ-Δ)
OUT–
SYNC
OUTPUT
SYNCO
INTERNAL
OSCILLATOR
FET
DRIVER
SYNC
OUT+
MODULATOR
(Σ-Δ)
OUT–
SYNC
OUTPUT
SYNCO
INTERNAL
OSCILLATOR
FET
DRIVER
SYNC
SYNCI
SYNCI
SYNCI
SYNC
INPUT
SYNC
INPUT
SYNC
INPUT
Figure 35. Typical SYNC Master-Slave Daisy-Chain Configuration
Rev. 0 | Page 13 of 20
OUT–
SYNC
OUTPUT
SYNCO
07550-036
SSM2319
SSM2319
THEORY OF OPERATION
OVERVIEW
OUTPUT MODULATION DESCRIPTION
The SSM2319 mono 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 SSM2319 does not require an output filter. Instead, it 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
SSM2319 uses a 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 reduces the amplitude of spectral
components at high frequencies, reducing EMI emission that
may 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 SSM2319 amplifiers.
The SSM2319 uses 3-level Σ-Δ output modulation. Each output
is able to 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 the
constant presence of noise, a differential pulse is generated
in response to this stimulus. A small amount of current flows
into the inductive load when the differential pulse is generated.
GAIN
When the user wants to send an input signal, an output pulse is
generated to follow the input voltage. The differential pulse density
is increased by raising the input signal level. Figure 36 depicts
3-level Σ-Δ output modulation with and without input stimulus.
OUTPUT = 0V
OUT+
0V
+5V
OUT–
0V
+5V
VOUT
The SSM2319 has a default gain of 12 dB that can be reduced by
using a pair of external resistors with a value calculated as follows:
0V
–5V
OUTPUT > 0V
OUT+
External Gain Settings = 160 kΩ/(40 kΩ + REXT)
Voltage transients at the output of the audio amplifiers can 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 can be generated
when the amplifier system changes its operating mode. For
example, audible transient sources include system power-up/
power-down, mute/unmute, an input source change, and a sample
rate change. The SSM2319 has a pop-and-click suppression
architecture that reduces these output transients, resulting in
noiseless activation and deactivation.
0V
+5V
VOUT
0V
OUTPUT < 0V
OUT+
OUT–
VOUT
+5V
0V
+5V
OUT–
POP-AND-CLICK SUPPRESSION
+5V
+5V
0V
+5V
0V
0V
–5V
07550-034
The SSM2319 also offers protection circuits for overcurrent and
temperature protection.
However, most of the time, the output differential voltage is 0 V,
due to the Analog Devices, Inc., patented 3-level, Σ-Δ output
modulation feature. This feature ensures that the current flowing
through the inductive load is small.
Figure 36. 3-Level Σ-Δ Output Modulation With and Without Input Stimulus
Rev. 0 | Page 14 of 20
SSM2319
LAYOUT
POWER SUPPLY DECOUPLING
As output power continues to increase, care must be taken to
lay out PCB traces and wires properly between 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 lowest DCR and use 1 oz or 2 oz of copper PCB
traces to further reduce IR drops and inductance. A 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.
To ensure high efficiency, low 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, low ESR capacitor, usually
of 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
SSM2319 helps to maintain efficient performance.
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 to the 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 layouts isolate critical analog paths from
sources of high interference. High frequency circuits (analog
and digital) should be separated from low frequency circuits.
SYNCRONIZATION (SYNC) OPERATION
SYNC is the feature that allows an external clock signal to control
the modulator of the SSM2319. The SSM2319 can act in standalone
mode, act as a master device, or act as a slave device. Although
the inherent random switching frequency of the Analog Devices
patented 3-level PDM modulation virtually eliminates the need for
SYNC, this feature can be activated in the event that end users are
concerned about clock intermodulation (beating effect) of several
amplifiers in close proximity.
Properly designed multilayer PCBs can reduce EMI emissions
and increase immunity to the RF field by a factor of 10 or more
when 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.
Another use for the SYNC feature is its ability to adjust modulator
frequency to move harmonic interference to a less sensitive
frequency band in certain applications with very delicate
interference requirements.
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.
Modulator synchronization is initiated after the internal shutdown signal is released. SYNCO buffers the internal oscillator
clock with a delay of 127 clock cycles.
INPUT CAPACITOR SELECTION
The SSM2319 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 using a single-ended source. If highpass filtering is needed at the input, the input capacitor, along
with the input resistor of the SSM2319, form a high-pass filter
whose corner frequency is determined by
fC = 1/{2π × (40 kΩ + REXT) × CIN}
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 PSRR performance.
Although the synchronization frequency operates from 5 MHz to
12 MHz, the optimal operating range is 6 MHz to 9 MHz.
When synchronizing several SSM2319 amplifiers, configure
them in a daisy-chain configuration, as shown in Figure 35.
Using this configuration causes a small delay in the SYNCO-toSYNCO transitions of multiple SSM2319s, preventing large
surges of instantaneous current and reducing excessive loading
of the power supply.
When configuring one device to act as a master device, it is
mandatory that the connection from SYNCO to SYCNI be less
than 1 mm. As in many digital systems, to maintain signal integrity
when interfacing several clocking systems, users must insert series
dumping resistors close to the SYNCO pin if long trace lengths
are used for synchronization connections. A typical value used
is 750 Ω. The series dumping resistor should be placed as close
to the SYNCO pin as possible. If careful layout practices are
followed to minimize signal trace routing from the SYNCO pin
of one device to the SYNCI pin of another, a dumping resistor is
not necessary. If the SYNC feature is not used, or if the SYNC
feature is not interfacing the SYNCO pin to an external device,
it is recommended that the SYNCO pin be floated.
Rev. 0 | Page 15 of 20
SSM2319
•
SYNCI = external clock. SYNCO is a buffered clock output
sourced from an external clock signal. One clock cycle after
the internal modulator detect signal is released, an irregular
pulse appears on MCLK before the first buffered output signal
begins on SYNCO, as shown in Figure 39.
The SYNC operating modes include the following:
SD
INTERNAL REF
SIGNAL MOD
SYNCI = GND or VDD. SYNCO stops generating pulses.
The modulator is controlled by an internal clock signal, as
shown in Figure 37.
SYNCI
SYNCO
MCLK
SYNCI = CLKIN
Figure 39. SYNCI = External Clock
SD
REF
INTERNAL
SIGNAL MOD
•
SYNCI = GND, transitions to clock. When the SYNCI pin is
connected to GND first but then transitions to a clock signal,
SYNCO generates several internal clock signals before finally
being synchronized to the external clock signal, as shown
in Figure 40.
SYNCI
07550-037
SYNCO
MCLK
SYNCI = GND
Figure 37. SYNCI = GND or VDD
SYNCI = SYNCO. SYNCO is the delayed clock signal of
SYNCI, as shown in Figure 38.
SYNCI
SYNCO
SD
MCLK
INTERNAL REF
SIGNAL MOD
SYNCI = GND TO CLKIN
Figure 40. SYNCI = GND to Clock Input
SYNCI
•
SYNCO
MCLK
SYNCI = SYNCO
SYNCI = CLK, transitions to GND. When SYNCI is
connected to a clock signal but then transitions to GND,
the SYNCO pin immediately stops generating a clock signal.
After a short clock loss detect time, the internal modulator
synchronizes to the internal clock signal, as shown
in Figure 41.
07550-038
•
SD
INTERNAL REF
SIGNAL MOD
07550-040
•
Initial SYNC startup. An internal reference signal, REF, is
released after one complete internal clock cycle (MCLK).
After REF is released, another internal signal, MOD, waits
127 internal clock cycles. This operates as a training signal
to determine the SYNCI/SYNCO connection. During this
time, SYNCO is the internal clock signal.
Figure 38. SYNCI = SYNCO
SD
INTERNAL REF
SIGNAL MOD
SYNCI
SYNCO
CLK LOSS
DETECT
MCLK
SYNCI = CLKIN TO GND
Figure 41. SYNCI = Clock Input to GND
Rev. 0 | Page 16 of 20
07550-041
•
07550-039
Operating Modes
SSM2319
OUTLINE DIMENSIONS
1.490
1.460 SQ
1.430
SEATING
PLANE
3
2
A
0.350
0.320
0.290
B
C
0.50
BALL PITCH
TOP VIEW
(BALL SIDE DOWN)
0.385
0.360
0.335
1
BOTTOM VIEW
0.270
0.240
0.210
(BALL SIDE UP)
101507-C
A1 BALL
CORNER
0.655
0.600
0.545
Figure 42. 9-Ball Wafer Level Chip Scale Package [WLCSP]
(CB-9-2)
Dimensions shown in millimeters
ORDERING GUIDE
Model
SSM2319CBZ-R2 1
SSM2319CBZ-REEL1
SSM2319CBZ-REEL71
EVAL-SSM2319Z1
1
Temperature Range
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
Package Description
9-Ball Wafer Level Chip Scale Package [WLCSP]
9-Ball Wafer Level Chip Scale Package [WLCSP]
9-Ball Wafer Level Chip Scale Package [WLCSP]
Evaluation Board
Z = RoHS Compliant Part.
Rev. 0 | Page 17 of 20
Package Option
CB-9-2
CB-9-2
CB-9-2
SSM2319
NOTES
Rev. 0 | Page 18 of 20
SSM2319
NOTES
Rev. 0 | Page 19 of 20
SSM2319
NOTES
©2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D07550-0-8/08(0)
Rev. 0 | Page 20 of 20