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Stereo CODEC with Speaker Driver
DESCRIPTION
The WM8978 is a low power, high quality stereo CODEC
designed for portable applications such as multimedia phone,
digital still camera or digital camcorder.
The device integrates preamps for stereo differential mics, and
includes drivers for speakers, headphone and differential or
stereo line output. External component requirements are
reduced as no separate microphone or headphone amplifiers
are required.
Advanced on-chip digital signal processing includes a 5-band
equaliser, a mixed signal Automatic Level Control for the
microphone or line input through the ADC as well as a purely
digital limiter function for record or playback. Additional digital
filtering options are available in the ADC path, to cater for
application filtering such as ‘wind noise reduction’.
The WM8978 digital audio interface can operate as a master or
a slave. An internal PLL can generate all required audio clocks
for the CODEC from common reference clock frequencies, such
as 12MHz and 13MHz.
The WM8978 operates at analogue supply voltages from 2.5V to
3.3V, although the digital core can operate at voltages down to
1.71V to save power. The speaker outputs and OUT3/4 line
outputs can run from a 5V supply if increased output power is
required. Individual sections of the chip can also be powered
down under software control.
WM8978
FEATURES
Stereo CODEC:
DAC SNR 98dB, THD -84dB (‘A’ weighted @ 48kHz)
ADC SNR 95dB, THD -84dB (‘A’ weighted @ 48kHz)
On-chip Headphone Driver with ‘capless’ option
-
40mW per channel into 16 / 3.3V SPKVDD
1W output power into 8 BTL speaker / 5V SPKVDD
-
Capable of driving piezo speakers
-
Stereo speaker drive configuration
Mic Preamps:
Stereo Differential or mono microphone Interfaces
-
Programmable preamp gain
-
Psuedo differential inputs with common mode
rejection
-
Programmable ALC / Noise Gate in ADC path
Low-noise bias supplied for electret microphones
Other Features:
Enhanced 3-D function for improved stereo separation
Digital playback limiter
5-band Equaliser (record or playback)
Programmable ADC High Pass Filter (wind noise reduction)
Programmable ADC Notch Filter
Aux inputs for stereo analogue input signals or ‘beep’
On-chip PLL supporting 12, 13, 19.2MHz and other clocks
Support for 8, 11.025, 12, 16, 22.05, 24, 32, 44.1 and
48kHz sample rates
Low power, low voltage
-
2.5V to 3.6V (digital: 1.71V to 3.6V)
5x5mm 32-lead QFN package
APPLICATIONS
BLOCK DIAGRAM
Stereo Camcorder or DSC
Multimedia Phone
WOLFSON MICROELECTRONICS plc
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Production Data, October 2011, Rev 4.5
Copyright
2011
Wolfson Microelectronics plc
WM8978
TABLE OF CONTENTS
Production Data
DESCRIPTION ....................................................................................................... 1
BLOCK DIAGRAM ................................................................................................ 1
FEATURES ............................................................................................................ 1
APPLICATIONS..................................................................................................... 1
TABLE OF CONTENTS ......................................................................................... 2
PIN CONFIGURATION .......................................................................................... 4
ORDERING INFORMATION .................................................................................. 4
PIN DESCRIPTION ................................................................................................ 5
ABSOLUTE MAXIMUM RATINGS ........................................................................ 6
RECOMMENDED OPERATING CONDITIONS ..................................................... 6
ELECTRICAL CHARACTERISTICS ..................................................................... 7
TERMINOLOGY ............................................................................................................ 10
SPEAKER OUTPUT THD VERSUS POWER ...................................................... 11
POWER CONSUMPTION .................................................................................... 12
AUDIO PATHS OVERVIEW ................................................................................ 14
SIGNAL TIMING REQUIREMENTS .................................................................... 15
SYSTEM CLOCK TIMING ............................................................................................. 15
AUDIO INTERFACE TIMING – MASTER MODE .......................................................... 15
AUDIO INTERFACE TIMING – SLAVE MODE ............................................................. 16
CONTROL INTERFACE TIMING – 3-WIRE MODE ...................................................... 17
CONTROL INTERFACE TIMING – 2-WIRE MODE ...................................................... 18
INTERNAL POWER ON RESET CIRCUIT .......................................................... 19
DEVICE DESCRIPTION ...................................................................................... 21
INTRODUCTION ........................................................................................................... 21
INPUT SIGNAL PATH ................................................................................................... 23
ANALOGUE TO DIGITAL CONVERTER (ADC) ........................................................... 30
INPUT LIMITER / AUTOMATIC LEVEL CONTROL (ALC)............................................ 36
OUTPUT SIGNAL PATH ............................................................................................... 47
3D STEREO ENHANCEMENT ...................................................................................... 54
ANALOGUE OUTPUTS ................................................................................................. 54
DIGITAL AUDIO INTERFACES ..................................................................................... 70
AUDIO SAMPLE RATES ............................................................................................... 75
MASTER CLOCK AND PHASE LOCKED LOOP (PLL) ................................................ 75
LOOPBACK ................................................................................................................... 77
COMPANDING .............................................................................................................. 77
GENERAL PURPOSE INPUT/OUTPUT........................................................................ 79
OUTPUT SWITCHING (JACK DETECT)....................................................................... 80
CONTROL INTERFACE ................................................................................................ 82
RESETTING THE CHIP ................................................................................................ 83
POWER SUPPLIES....................................................................................................... 83
RECOMMENDED POWER UP/DOWN SEQUENCE .................................................... 83
POWER MANAGEMENT .............................................................................................. 88
REGISTER MAP .................................................................................................. 89
REGISTER BITS BY ADDRESS ................................................................................... 91
DIGITAL FILTER CHARACTERISTICS ............................................................ 108
TERMINOLOGY .......................................................................................................... 108
DAC FILTER RESPONSES ........................................................................................ 109
ADC FILTER RESPONSES ........................................................................................ 109
HIGHPASS FILTER ..................................................................................................... 110
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Production Data
WM8978
5-BAND EQUALISER .................................................................................................. 111
APPLICATION INFORMATION ......................................................................... 115
RECOMMENDED EXTERNAL COMPONENTS ......................................................... 115
PACKAGE DIAGRAM ....................................................................................... 116
IMPORTANT NOTICE ....................................................................................... 117
ADDRESS ................................................................................................................... 117
REVISION HISTORY ......................................................................................... 118
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WM8978
PIN CONFIGURATION
Production Data
ORDERING INFORMATION
ORDER CODE
WM8978CGEFL/V
WM8978CGEFL/RV
Note:
Reel quantity = 3,500
TEMPERATURE
RANGE
-40C to +100C
-40C to +100C
PACKAGE
32-lead QFN (5 x 5 mm)
(Pb-free)
32-lead QFN (5 x 5 mm)
(Pb-free, tape and reel)
MOISTURE
SENSITIVITY LEVEL
MSL3
MSL3
PEAK SOLDERING
TEMPERATURE
260 C
260 C
o
o
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Production Data
WM8978
PIN DESCRIPTION
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
NAME
LIP
LIN
L2/GPIO2
RIP
RIN
R2/GPIO3
LRC
BCLK
ADCDAT
DACDAT
MCLK
DGND
DCVDD
DBVDD
CSB/GPIO1
SCLK
SDIN
MODE
AUXL
AUXR
OUT4
OUT3
ROUT2
SPKGND
LOUT2
SPKVDD
VMID
AGND
ROUT1
LOUT1
AVDD
MICBIAS
TYPE
Analogue input
Analogue input
Analogue input
Analogue input
Analogue input
Analogue input
Digital Input / Output
Digital Input / Output
Digital Output
Digital Input
Digital Input
Supply
Supply
Supply
Digital Input / Output
Digital Input
Digital Input / Output
Digital Input
Analogue input
Analogue input
Analogue Output
Analogue Output
Analogue Output
Supply
Analogue Output
Supply
Reference
Supply
Analogue Output
Analogue Output
Supply
Analogue Output
DESCRIPTION
Left Mic Pre-amp positive input
Left Mic Pre-amp negative input
Left channel line input/secondary mic pre-amp positive input/GPIO2 pin
Right Mic Pre-amp positive input
Right Mic Pre-amp negative input
Right channel line input/secondary mic pre-amp positive input/GPIO3 pin
DAC and ADC Sample Rate Clock
Digital Audio Port Clock
ADC Digital Audio Data Output
DAC Digital Audio Data Input
Master Clock Input
Digital ground
Digital core logic supply
Digital buffer (I/O) supply
3-Wire Control Interface Chip Select / GPIO1 pin
3-Wire Control Interface Clock Input / 2-Wire Control Interface Clock
Input
3-Wire Control Interface Data Input / 2-Wire Control Interface Data Input
Control Interface Selection
Left Auxillary input
Right Auxillary input
Buffered midrail Headphone pseudo-ground, or Right line output or MONO
mix output
Buffered midrail Headphone pseudo-ground, or Left line output
Second right output, or BTL speaker driver positive output
Speaker ground (feeds speaker amp and OUT3/OUT4)
Second left output, or BTL speaker driver negative output
Speaker supply (feed speaker amp only)
Decoupling for ADC and DAC reference voltage
Analogue ground (feeds ADC and DAC)
Headphone or Line Output Right
Headphone or Line Output Left
Analogue supply (feeds ADC and DAC)
Microphone Bias
Note:
It is recommended that the QFN ground paddle should be connected to analogue ground on the application PCB. Refer to
the application note WAN_0118 on “Guidelines on How to Use QFN Packages and Create Associated PCB Footprints”.
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