Built-in four-conductor headset jack support with in-
line command sensing
Hum noise is prevented on external powered speakers
plugged into the headset jack when the system is off
Universal jack supports headsets, headphones,
external microphones, and external line-in devices
Digital Microphone Interface (DMIC) with boost
supporting two digital microphone elements and DC
offset removal
Record security prevents unwanted recordings from all
or selected input ports
Analog and digital PC Beep are supported, and Wake-
on-beep never misses a beep—even when in low-
power mode
Multiple General Purpose Input/Outputs (GPIOs) for
custom applications
Integrated Low Drop-Out (LDO) regulators
Headphone limiter supports GS Mark EN50332-2
without an external Bill Of Materials (BOM)
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Applications
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Notebooks
Ultrabooks
Desktop and all-in-one PCs
Tablets
Embedded applications
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System Compatibility
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HD Audio Specification 1.0a
Windows XP/Vista/7/8.x
Microsoft Premium Logo
Linux
Android
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01/08/15
Conexant Confidential
• www.conexant.com
004-56DSR01
CX20756 Data Sheet
Revision History
Revision History
Document No.
004-56DSR01
004-56DSR00
Release Date Change Description
01/08/15
08/05/14
Added 1.8V HD link signaling support.
Initial release.
Conexant Confidential
01/08/15
004-56DSR01
ii
CX20756 Data Sheet
Table of Contents
Table of Contents
General Description.......................................................................................................................................................i
System Compatibility ....................................................................................................................................................i
Revision History ...........................................................................................................................................................ii
System Compatibility .......................................................................................................................................................... 3
Hardware Qualification Process (HQP).............................................................................................................................. 3
General ................................................................................................................................................................................. 4
High Definition (HD) Audio Host Interface .................................................................................................................. 4
Control Signals ........................................................................................................................................................... 4
Pin Assignments and Signal Definitions........................................................................................................................... 6
Absolute Maximum Ratings.............................................................................................................................................. 12
Power Management and Power Consumption................................................................................................................ 17
Power Management.................................................................................................................................................. 17
Power Supply Minimum/Maximum Ratings .............................................................................................................. 17
Power Consumption ................................................................................................................................................. 18
Digital High-Pass Filter (HPF)................................................................................................................................... 20
Alternating Current (AC) Timing Characteristics............................................................................................................ 21
Digital Microphone Interface (DMIC) ........................................................................................................................ 21
HD Audio Clocks....................................................................................................................................................... 22
Data Output and Input .............................................................................................................................................. 23
Package Dimensions and Thermal Specifications ......................................................................................................... 24
HD Audio Interface......................................................................................................................................................26
Node ID 00: Root Node ............................................................................................................................................ 28
Node ID 01: Audio Function Group (AFG)................................................................................................................ 29
Node 16: Port A/Vendor Widget ............................................................................................................................... 36
Node 17: Port G........................................................................................................................................................ 37
Node 18: Port B Widget ............................................................................................................................................ 38
Node 19: Port D Widget............................................................................................................................................ 40
Node 1A: Port C Widget ........................................................................................................................................... 41
Figure 3: CX20756 40-QFN Pad Signals.......................................................................................................................................... 7
Figure 4: Power Supply Rejection for Class-D Amplifier Output..................................................................................................... 15
Figure 5: Power Supply Rejection for Headphone Amplifier Output ............................................................................................... 15
Figure 6: Class-D Output Power vs Load (1% THD) ...................................................................................................................... 16
Figure 8: Digital Microphone Clock Timing Waveform.................................................................................................................... 21
Figure 9: BIT_CLK and SYNC Timing Waveforms ......................................................................................................................... 22
Figure 10: Data Output and Input Timing Waveforms .................................................................................................................... 23
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