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Mono CODEC with Speaker Driver
DESCRIPTION
The WM8940 is a low power, high quality mono CODEC
designed for portable applications such as digital still cameras
or camcorders.
The device integrates support for a differential or single ended
mic, and includes drivers for speakers or headphone, and
mono line output. External component requirements are
reduced as no separate microphone or headphone amplifiers
are required.
Advanced Sigma Delta Converters are used along with digital
decimation and interpolation filters to give high quality audio at
sample rates from 8 to 48ks/s. A selectable high pass filter
and four fully-programmable notch filters are available in the
ADC path. An advanced mixed signal ALC function with noise
gate is provided, while readback of PGA gain during ALC
operation is supported. The digital audio interface supports A-
law and
µ-law
companding.
An on-chip PLL is provided to generate the required Master
Clock from an external reference clock. The PLL clock can
also be output if required elsewhere in the system.
The WM8940 operates at supply voltages from 2.5 to 3.6V,
although the digital supplies can operate at voltages down to
1.71V to save power. Different sections of the chip can also be
powered down under software control using the selectable two
or three wire control interface.
WM8940 is supplied in a very small 4x4mm QFN package,
offering high levels of functionality in minimum board area,
with high thermal performance.
WM8940
FEATURES
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Mono CODEC:
Audio sample rates:8, 11.025, 16, 22.05, 24, 32, 44.1, 48kHz
DAC SNR 98dB, THD -84dB (‘A’-weighted @ 8 – 48ks/s)
ADC SNR 94dB, THD -80dB (‘A’-weighted @ 8 – 48ks/s)
On-chip Headphone/Speaker Driver
- 40mW output power into 16Ω
- BTL speaker drive 0.4W into 8Ω
Additional MONO Line output
Multiple analog or ‘Aux’ inputs, plus analog bypass path
Mic Preamps:
Differential or single end Microphone Interface
- Programmable preamp gain
- Pseudo differential inputs with common mode rejection
- Programmable ALC / Noise Gate in ADC path
Low-noise bias supplied for electret microphones
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OTHER FEATURES
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Digital Playback Limiter
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Programmable high pass filter (wind noise reduction)
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4 notch filters (narrowband noise suppression)
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On-chip PLL
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Low power, low voltage
- 2.5V to 3.6V (digital: 1.71V to 3.6V)
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4x4x0.9mm 24 lead QFN package
APPLICATIONS
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Digital still cameras and camcorders
General purpose mono audio CODEC
WOLFSON MICROELECTRONICS plc
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Production Data, Rev 4.2, April 2008
Copyright
©2008
Wolfson Microelectronics plc
WM8940
BLOCK DIAGRAM
Production Data
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Production Data
WM8940
TABLE OF CONTENTS
DESCRIPTION .......................................................................................................1
FEATURES.............................................................................................................1
APPLICATIONS .....................................................................................................1
BLOCK DIAGRAM .................................................................................................2
TABLE OF CONTENTS .........................................................................................3
PIN CONFIGURATION...........................................................................................5
ORDERING INFORMATION ..................................................................................5
PIN DESCRIPTION ................................................................................................6
ABSOLUTE MAXIMUM RATINGS.........................................................................7
RECOMMENDED OPERATING CONDITIONS .....................................................7
ELECTRICAL CHARACTERISTICS ......................................................................8
TERMINOLOGY .......................................................................................................... 10
AUDIO PATHS OVERVIEW .................................................................................11
SIGNAL TIMING REQUIREMENTS .....................................................................13
SYSTEM CLOCK TIMING ........................................................................................... 13
AUDIO INTERFACE TIMING – MASTER MODE ........................................................ 13
AUDIO INTERFACE TIMING – SLAVE MODE............................................................ 14
CONTROL INTERFACE TIMING – 3-WIRE MODE .................................................... 15
CONTROL INTERFACE TIMING – 2-WIRE MODE .................................................... 16
DEVICE DESCRIPTION.......................................................................................17
INTRODUCTION ......................................................................................................... 17
INPUT SIGNAL PATH ................................................................................................. 18
ANALOGUE TO DIGITAL CONVERTER (ADC).......................................................... 23
INPUT LIMITER / AUTOMATIC LEVEL CONTROL (ALC) .......................................... 28
OUTPUT SIGNAL PATH ............................................................................................. 41
ANALOGUE OUTPUTS............................................................................................... 45
OUTPUT SWITCH ...................................................................................................... 48
DIGITAL AUDIO INTERFACES................................................................................... 51
AUDIO SAMPLE RATES ............................................................................................. 55
MASTER CLOCK AND PHASE LOCKED LOOP (PLL) ............................................... 55
COMPANDING............................................................................................................ 58
GENERAL PURPOSE INPUT/OUTPUT...................................................................... 60
CONTROL INTERFACE.............................................................................................. 61
3-WIRE SERIAL CONTROL MODE ............................................................................ 62
READBACK IN 3-WIRE MODE ................................................................................... 62
2-WIRE SERIAL CONTROL MODE ............................................................................ 63
RESETTING THE CHIP .............................................................................................. 64
POWER SUPPLIES .................................................................................................... 64
POWER MANAGEMENT ............................................................................................ 66
POP MINIMISATION ................................................................................................... 67
REGISTER MAP...................................................................................................68
REGISTER BITS BY ADDRESS ................................................................................. 69
DIGITAL FILTER CHARACTERISTICS ...............................................................80
TERMINOLOGY .......................................................................................................... 80
DAC FILTER RESPONSES......................................................................................... 81
ADC FILTER RESPONSES......................................................................................... 81
HIGHPASS FILTER..................................................................................................... 82
NOTCH FILTERS AND LOW PASS FILTER............................................................... 83
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WM8940
Production Data
NOTCH FILTER WORKED EXAMPLE........................................................................ 84
APPLICATIONS INFORMATION .........................................................................85
RECOMMENDED EXTERNAL COMPONENTS .......................................................... 85
PACKAGE DIAGRAM ..........................................................................................86
IMPORTANT NOTICE ..........................................................................................87
ADDRESS ................................................................................................................... 87
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Production Data
WM8940
PIN CONFIGURATION
TOP VIEW
ORDERING INFORMATION
ORDER CODE
WM8940GEFL/V
WM8940GEFL/RV
Note:
Reel Quantity = 3,500
TEMPERATURE
RANGE
-25°C to +85°C
-25°C to +85°C
PACKAGE
24-lead QFN (4x4x0.9mm)
(Pb-free)
24-lead QFN (4x4x0.9mm)
(Pb-free, tape and reel)
MOISTURE SENSITIVITY
LEVEL
MSL3
MSL3
PACKAGE BODY
TEMPERATURE
260
o
C
260
o
C
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