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WM9082
PDM Input Mono 3W Class D Speaker Driver
DESCRIPTION
FEATURES
The WM9082 is a high-performance sigma-delta Class D
speaker driver. Audio input is supported using a stereo PDM
interface; clock and control-code detection circuitry supports
all of the audio and control functions via a 2-wire interface.
The digital audio interface provides excellent noise
immunity, eliminating traditional input-filtering components.
The flexible 2-wire interface minimises the PCB footprint and
simplifies software development.
The combined audio and control interface configuration is
ideal for enabling the WM9082 to be located close to the
speaker; this reduces the length of the output connections,
giving good EMC performance and removing the need for
output filter components.
The sigma-delta architecture provides good power efficiency
and improved EMI performance with respect to traditional
PWM Class D designs.
Sigma-Delta Class-D speaker driver
-
92dB SNR - ‘A’ weighted
2.5W into 4 (5V supply, 1% THD)
-
1.3W into 4 (3.6V supply, 1% THD)
-
1.25W into 8 (5V supply, 1% THD)
-
650mW into 8 (3.6V supply, 1% THD
Stereo PDM digital audio input
Supports 32kHz, 44.1kHz, 48kHz sample rates (128fs input)
Automatic Left/Right channel selection
First-order high pass filter (HPF)
RF noise suppression
Pop and click suppression
Programmable output slew rates for low EMI
Short-circuit and thermal protection
9-ball CSP package
A first-order high-pass filter can be selected on the input
signal to remove DC offsets and help to prevent speaker
damage. Other features include a low-power mute state,
and output slew-rate control.
APPLICATIONS
Short-circuit and thermal protection is provided.
The WM9082 is supplied in a 9-ball 1.56 x 1.46mm CSP
package, with 0.5mm ball pitch.
Mobile Handsets
Portable Media Players (PMP)
Notebooks / Laptop computers
LCD televisions
BLOCK DIAGRAM
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Production Data, August 2012, Rev 4.1
Copyright 2012 Wolfson Microelectronics plc
WM9082
Production Data
TABLE OF CONTENTS
DESCRIPTION ....................................................................................................... 1
FEATURES ............................................................................................................ 1
APPLICATIONS..................................................................................................... 1
BLOCK DIAGRAM ................................................................................................ 1
TABLE OF CONTENTS ......................................................................................... 2
PIN CONFIGURATION .......................................................................................... 3
ORDERING INFORMATION .................................................................................. 3
PIN DESCRIPTION ................................................................................................ 3
ABSOLUTE MAXIMUM RATINGS ........................................................................ 4
RECOMMENDED OPERATING CONDITIONS ..................................................... 4
ELECTRICAL CHARACTERISTICS ..................................................................... 5
TERMINOLOGY ............................................................................................................... 6
TYPICAL PERFORMANCE ................................................................................... 7
SIGNAL TIMING REQUIREMENTS ...................................................................... 8
PDM AUDIO INTERFACE TIMING .................................................................................. 8
DEVICE DESCRIPTION ........................................................................................ 9
INTRODUCTION .............................................................................................................. 9
PDM AUDIO INTERFACE ................................................................................................ 9
DEVICE CONTROL CODES .......................................................................................... 10
INITIAL POWER-UP .................................................................................................................................. 12
CONFIGURATION EVENTS ..................................................................................................................... 12
START-UP EVENTS ................................................................................................................................. 13
STANDBY EVENTS .................................................................................................................................. 14
SHUTDOWN EVENTS .............................................................................................................................. 14
STATE TRANSITION DIAGRAM ............................................................................................................... 15
SPEAKER DRIVER ........................................................................................................ 16
RESETS AND SHUTDOWN .......................................................................................... 16
APPLICATIONS INFORMATION ........................................................................ 17
RECOMMENDED EXTERNAL COMPONENTS ............................................................ 17
PCB LAYOUT CONSIDERATIONS ............................................................................... 20
PACKAGE DIMENSIONS .................................................................................... 21
PACKAGE DIAGRAM FOR DEVICES MARKED LT9 ................................................... 21
PACKAGE DIAGRAM FOR DEVICES MARKED JC5 ................................................... 22
IMPORTANT NOTICE ......................................................................................... 23
ADDRESS: ..................................................................................................................... 23
REVISION HISTORY ........................................................................................... 24
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WM9082
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PIN CONFIGURATION
The WM9082 is supplied in a 9-ball CSP format. The pin configuration is illustrated below, showing
the top-down view from above the chip.
ORDERING INFORMATION
ORDER CODE
TEMPERATURE RANGE
PACKAGE
MOISTURE
SENSITIVITY LEVEL
PEAK SOLDERING
TEMPERATURE
-40C to +85C
9-ball CSP
(Pb-free, tape and reel)
MSL1
260 C
WM9082ECSN/R
o
Note:
Reel quantity = 5,000
PIN DESCRIPTION
PIN NO
NAME
A1
SPKOUTP
A2
DNC
A3
TYPE
DESCRIPTION
Analogue Output
Positive BTL speaker output
GND
Supply
Ground
B1
SPKVDD
Supply
Class D output driver supply
B2
SPKGND
Supply
Ground
B3
DVDD
Supply
Digital supply
C1
SPKOUTN
Analogue Output
Negative BTL speaker output
C2
IN2
Digital Input
PDM input (CLK or Left DATA input)
C3
IN1
Digital Input
PDM input (CLK or Right DATA input)
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ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are stress ratings only. Permanent damage to the device may be caused by continuously
operating at or beyond these limits. Device functional operating limits and guaranteed performance specifications are given
under Electrical Characteristics at the test conditions specified.
ESD Sensitive Device. This device is manufactured on a CMOS process. It is therefore generically susceptible
to damage from excessive static voltages. Proper ESD precautions must be taken during handling and storage
of this device.
Wolfson tests its package types according to IPC/JEDEC J-STD-020B for Moisture Sensitivity to determine acceptable storage
conditions prior to surface mount assembly. These levels are:
MSL1 = unlimited floor life at 24
consecutive 0’s is received on the PDM audio interface.)
Table 8 WM9082 Standby Events
Note that repeated instances of any Control Code will not cause more than one state transition until
audio data or a different Control Code has been received. This prevents the WM9082 from cycling
between the “ON” state and the “STANDBY” state in the event of repeated Control Codes.
SHUTDOWN EVENTS
If the CLK input is not present at any time, this results in a transition to the “OFF” state. The WM9082
will remain in the “OFF” state until the CLK input restarts.
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WM9082
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STATE TRANSITION DIAGRAM
The WM9082 operating states and transitions are illustrated in Figure 3.
Figure 3 State Transition Diagram
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SPEAKER DRIVER
The speaker outputs SPKOUTP and SPKOUTN operate in a BTL configuration. These pins provide a
differential output for direct connection to the loudspeaker. In a typical application, no other external
components are required for the loudspeaker connection.
The sigma-delta architecture of the Class D driver is more linear and power efficient than traditional
PWM implementations, resulting in reduced power consumption and improved EMI characteristics.
The speaker driver is disabled during start-up and following receipt of selected Control Codes which
can be used to configure the WM9082. The driver is automatically re-enabled on receipt of any audio
data.
RESETS AND SHUTDOWN
A power on reset circuit ensures correct start-up and shut-down when the DVDD supply rail is
enabled or disabled.
The WM9082 is held in the “OFF” state when there is no CLK signal detected on the IN1 or IN2 pins;
the Shutdown current in the “OFF” state is noted in the “Electrical Characteristics” section.
Short circuit and thermal protection is also provided. In the event of an output short-circuit or an overtemperature condition, the WM9082 will protect itself by disabling the Class D speaker driver. The
WM9082 will automatically recover and continue normal operation when the fault condition is cleared.
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WM9082
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APPLICATIONS INFORMATION
RECOMMENDED EXTERNAL COMPONENTS
POWER SUPPLY DECOUPLING
Electrical coupling exists particularly in digital logic systems where switching in one sub-system
causes fluctuations on the power supply. This effect occurs because the inductance of the power
supply acts in opposition to the changes in current flow that are caused by the logic switching. The
resultant variations (or ‘spikes’) in the power supply voltage can cause malfunctions and unintentional
behaviour in other components. A decoupling (or ‘bypass’) capacitor can be used as an energy
storage component which will provide power to the decoupled circuit for the duration of these power
supply variations, protecting it from malfunctions that could otherwise arise.
Coupling also occurs in a lower-frequency form when ripple is present on the power supply rail
caused by changes in the load current or by limitations of the power supply regulation method. In
audio components such as the WM9082, these variations can alter the performance of the signal
path, leading to degradation in signal quality. A decoupling (or ‘bypass’) capacitor can be used to filter
these effects, by presenting the ripple voltage with a low impedance path that does not affect the
circuit to be decoupled.
These coupling effects are addressed by placing a capacitor between the supply rail and the
corresponding ground reference. In the case of systems comprising multiple power supply rails,
decoupling should be provided on each rail.
The recommended power supply decoupling capacitors for WM9082 are listed below in Table 9.
POWER SUPPLY
DECOUPLING CAPACITOR
DVDD
0.1F ceramic
SPKVDD
4.7F ceramic
Table 9 Power Supply Decoupling Capacitors
All decoupling capacitors should be placed as close as possible to the WM9082 device.
Due to the wide tolerance of many types of ceramic capacitors, care must be taken to ensure that the
selected components provide the required capacitance across the required temperature and voltage
ranges in the intended application. For most application the use of ceramic capacitors with capacitor
dielectric X5R is recommended.
CLASS D SPEAKER CONNECTIONS
The WM9082 incorporates a Class D speaker driver, which offers high amplifier efficiency at large
signal levels. As the Class D output is a sigma-delta modulated signal, the choice of speakers and
tracking of signals is important for ensuring good performance and reducing EMI.
The efficiency of the speaker drivers is affected by the series resistance between the WM9082 and
the speaker (e.g. PCB track loss and inductor ESR) as shown in Figure 4. This resistance should be
as low as possible to maximise efficiency.
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Figure 4 Speaker Connection Losses
The Class D output requires external filtering in order to recreate the audio signal. This may be
nd
implemented using a 2 order LC filter, or else may be achieved by using a loudspeaker whose
internal inductance provides the required filter response. An LC filter should be used if the
loudspeaker characteristics are unknown or unsuitable, or if the length of the loudspeaker connection
is likely to lead to EMI problems.
A suitable LC filter implementation is illustrated in Figure 5.
Figure 5 Class D Output Filter Components
A simple equivalent circuit of a loudspeaker consists of a serially connected resistor and inductor, as
shown in Figure 6. This circuit provides a low pass filter for the speaker output. If the loudspeaker
characteristics are suitable, then the loudspeaker itself can be used in place of the filter components
described earlier. This is known as ‘filterless’ operation.
Figure 6 Speaker Equivalent Circuit for Filterless Operation
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WM9082
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For filterless Class D operation, it is important to ensure that a speaker with suitable inductance is
chosen. For example, if we know the speaker impedance is 8Ω and the desired cut-off frequency is
20kHz, then the optimum speaker inductance may be calculated as:
8 loudspeakers typically have an inductance in the range 20H to 100H, however, it should be
noted that a loudspeaker inductance will not be constant across the relevant frequencies for Class D
operation (up to and beyond the Class D switching frequency).
The Class D outputs of the WM9082 operate at much higher frequencies than is recommended for
most speakers; care should be taken to ensure that the cut-off frequency of the loudspeaker’s filtering
is low enough to suppress the high frequency energy of the Class D switching and, in so doing, to
prevent speaker damage.
A simple test can be used to confirm if the loudspeaker is compatible with filterless operation. Under
quiescent input conditions (idle digital audio input while in the ON state), the SPKVDD current is
measured with the speaker disconnected, and measured again with the speaker connected. If the
SPKVDD current increases by more than 10mA when the speaker is connected, then the speaker
alone is not effective as a filter, and it is recommended to consider changing the speaker or adding
LC filter components.
RECOMMENDED EXTERNAL COMPONENTS DIAGRAM
Figure 7 provides a summary of recommended external components for WM9082. Note that the
actual requirements may differ according to the specific target application.
Figure 7 WM9082 Recommended External Components Diagram
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WM9082
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PCB LAYOUT CONSIDERATIONS
Poor PCB layout will degrade the performance and be a contributory factor in EMI, ground bounce
and resistive voltage losses. All external components should be placed as close to the WM9082
device as possible, with current loop areas kept as small as possible.
CLASS D LOUDSPEAKER CONNECTION
Long, exposed PCB tracks or connection wires will emit EMI. The distance between the WM9082 and
the loudspeaker should therefore be kept as short as possible. Where speakers are connected to the
PCB via a cable form, it is recommended that a shielded twisted pair cable is used. The shield should
be connected to the main system, with care taken to ensure ground loops are avoided.
Further reduction in EMI can be achieved using PCB ground (or VDD) planes and also by using
passive LC components to filter the Class D switching waveform. When passive filtering is used, low
ESR components should be chosen in order to minimise the series resistance between the WM9082
and the speaker, maximising the power efficiency.
LC passive filtering will usually be effective at reducing EMI at frequencies up to around 30MHz. To
reduce emissions at higher frequencies, ferrite beads can also be used. These should be positioned
as close to the device as possible.
These techniques for EMI reduction are illustrated in Figure 8.
SPKOUTP
WM9082
SPKOUTN
WM9082
SPKOUTN
WM9082
SPKOUTN
EMI
Long, exposed tracks emit EMI
SPKOUTP
Short connection wires will reduce EMI emission
SPKOUTP
Shielding using PCB ground (or VDD) planes
will reduce EMI emission
SPKOUTP
LOW ESR
WM9082
SPKOUTN
LOW ESR
WM9082
SPKOUTN
SPKOUTP
LC filtering will reduce EMI emission
up to around 30MHz
Ferrite beads will reduce EMI emission
at frequencies above 30MHz.
Figure 8 EMI Reduction Techniques
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WM9082
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PACKAGE DIMENSIONS
PACKAGE DIAGRAM FOR DEVICES MARKED LT9
B: 9 BALL W-CSP PACKAGE 1.560 X 1.460 X 0.635mm BODY, 0.50 mm BALL PITCH
A
4
D
DETAIL 1
A2
3
2
DM085.B
1
2
A1
CORNER
A
E1
B
E
4
e
3
C
4X
e
DETAIL 2
0.05
D1
BOTTOM VIEW
TOP VIEW
f1
SOLDER BALL
f2
h
1
Z
A1
DETAIL 1
DETAIL 2
Symbols
A
A1
A2
D
D1
E
E1
e
f1
f2
MIN
0.618
0.230
0.388
1.550
1.450
Dimensions (mm)
NOM
MAX
0.635
0.652
0.235
0.240
0.412
0.400
1.570
1.560
1.000 BSC
1.470
1.460
1.000 BSC
0.500 BSC
NOTE
3
0.275
0.225
h
0.320
NOTES:
1. PRIMARY DATUM -Z- AND SEATING PLANE ARE DEFINED BY THE SPHERICAL CROWNS OF THE SOLDER BALLS.
2. A1 CORNER IS IDENTIFIED BY INK/LASER MARK ON TOP PACKAGE.
3. ‘e’ REPRESENTS THE BASIC SOLDER BALL GRID PITCH.
4. THIS DRAWING IS SUBJECT TO CHANGE WITHOUT NOTICE.
5. FOLLOWS JEDEC DESIGN GUIDE MO-211-C.
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WM9082
Production Data
PACKAGE DIAGRAM FOR DEVICES MARKED JC5
B : 9 B A L L W -C S P P A C K A G E 1 .5 7 0 X 1 .4 7 0 X 0 .6 4 9 m m B O D Y , 0 .5 0 m m B A L L P IT C H
A
4
D
D E T A IL 1
A2
2
3
D M 0 8 5 .C
1
2
A1
CORNER
A
E1
B
E
4
e
3
C
4 X
e
D E T A IL 2
0 .0 2 5
D1
B O T T O M V IE W
T O P V IE W
f1
SOLDER BALL
f2
h
1
Z
A1
D E T A IL 1
D E T A IL 2
S y m b o ls
A
A1
A2
D
D1
E
E1
e
f1
M IN
0 .6 1 0
0 .2 1 2
0 .3 8 7
1 .5 4 5
1 .4 4 5
D im e n s io n s
NOM
0 .6 4 9
0 .2 4 9
0 .4 0 0
1 .5 7 0
1 .0 0 0 B S C
1 .4 7 0
1 .0 0 0 B S C
0 .5 0 0 B S C
(m m )
MAX
0 .6 8 8
0 .2 8 6
0 .4 1 3
1 .5 9 5
NO TE
1 .4 9 5
3
0 .2 7 3
f2
0 .2 2 3
h
0 .2 6 1
0 .3 1 1
0 .3 6 1
NO TES:
1 . P R IM A R Y D A T U M -Z - A N D S E A T IN G P L A N E A R E D E F IN E D B Y T H E S P H E R IC A L C R O W N S O F T H E S O L D E R B A L L S.
2 . A 1 C O R N E R IS ID E N T IF IE D B Y IN K /L A S E R M A R K O N T O P P A C K A G E .
3 . ‘e ’ R E P R E S E N T S T H E B A S IC S O L D E R B A L L G R ID P IT C H .
4 . T H IS D R A W IN G IS S U B J E C T T O C H A N G E W IT H O U T N O T IC E .
5 . F O L L O W S J E D E C D E S IG N G U ID E M O -2 1 1 -C .
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WM9082
IMPORTANT NOTICE
Wolfson Microelectronics plc (“Wolfson”) products and services are sold subject to Wolfson’s terms and conditions of sale,
delivery and payment supplied at the time of order acknowledgement.
Wolfson warrants performance of its products to the specifications in effect at the date of shipment. Wolfson reserves the
right to make changes to its products and specifications or to discontinue any product or service without notice. Customers
should therefore obtain the latest version of relevant information from Wolfson to verify that the information is current.
Testing and other quality control techniques are utilized to the extent Wolfson deems necessary to support its warranty.
Specific testing of all parameters of each device is not necessarily performed unless required by law or regulation.
In order to minimize risks associated with customer applications, the customer must use adequate design and operating
safeguards to minimise inherent or procedural hazards. Wolfson is not liable for applications assistance or customer
product design. The customer is solely responsible for its selection and use of Wolfson products. Wolfson is not liable for
such selection or use nor for use of any circuitry other than circuitry entirely embodied in a Wolfson product.
Wolfson’s products are not intended for use in life support systems, appliances, nuclear systems or systems where
malfunction can reasonably be expected to result in personal injury, death or severe property or environmental damage.
Any use of products by the customer for such purposes is at the customer’s own risk.
Wolfson does not grant any licence (express or implied) under any patent right, copyright, mask work right or other
intellectual property right of Wolfson covering or relating to any combination, machine, or process in which its products or
services might be or are used. Any provision or publication of any third party’s products or services does not constitute
Wolfson’s approval, licence, warranty or endorsement thereof. Any third party trade marks contained in this document
belong to the respective third party owner.
Reproduction of information from Wolfson datasheets is permissible only if reproduction is without alteration and is
accompanied by all associated copyright, proprietary and other notices (including this notice) and conditions. Wolfson is
not liable for any unauthorisedٛ alteration of such information or for any reliance placed thereon.
Any representations made, warranties given, and/or liabilities accepted by any person which differ from those contained in
this datasheet or in Wolfson’s standard terms and conditions of sale, delivery and payment are made, given and/or
accepted at that person’s own risk. Wolfson is not liable for any such representations, warranties or liabilities or for any
reliance placed thereon by any person.
ADDRESS:
Wolfson Microelectronics plc
26 Westfield Road
Edinburgh
EH11 2QB
United Kingdom
Tel :: +44 (0)131 272 7000
Fax :: +44 (0)131 272 7001
Email :: sales@wolfsonmicro.com
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WM9082
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REVISION HISTORY
DATE
REV
05/07/10
1.0
First Release
DESCRIPTION OF CHANGES
20/04/11
2.0
Product status updated to preliminary technical data
21/04/11
2.0
Updated pinout changing VREFC to DNC. All associated diagrams
and tables also updated to reflect the change
PAGE
CHANGED BY
1, 4, 16,
WF
18
28/04/11
2.0
PSRR typical electrical characteristics values added
5
BM
03/05/11
2.0
In Description, removed ‘The recommended configuration requires
only 3 external capacitors’
1
WF
12/08/11
2.1/2.2
Electrical Characteristics updated.
PH
Additional Control Codes defined for slew rate control &
performance mode.
Updates to filterless speaker description & recommendations
15/09/11
2.2
Electrical Characteristics updated
PH
Default slew rate / operating mode conditions updated
25/10/11
3.0
Product status updated to pre-production
18/05/12
4.0
Electrical Characteristics updated
JMacD
PH
Typical performance graphs added
10/08/12
4.1
Package Diagram DM085C added.
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