Cx31993 Datasheet Fix ^new^
Use the following verified register bitmasks for tracking the internal auxiliary ADC values: Play/Pause (Hook Switch): 0x00 (Direct short to ground) Volume Up: 0x1C to 0x24 Volume Down: 0x3A to 0x45 4. Summary Cheat Sheet: Datasheet Overrides Parameter / Pin Datasheet Value Verified Correct Value (Fix) MICBIAS Pull-up 4.7 kΩ Prevents mic audio clipping VBUS Decoupling 4.7 µF + 0.1 µF Eliminates USB ground hiss Reset Delay 20 ms Solves USB enumeration failure Stereo Channels Standard Pinout Invert HPL / HPR Layout Fixes swapped Left/Right audio
Digital Ground (DGND) and Analog Ground (AGND) connect at a single point (star ground) under the chip using a 0-ohm resistor or net tie. Audio & Controls HPLcap H cap P cap L HPRcap H cap P cap R
The Conexant (now Synaptics) CX31993 is a highly popular, low-power USB Type-C digital-to-analog converter (DAC) and audio codec. It is widely used in portable headphone dongles, smartphones, and DIY audio projects due to its excellent signal-to-noise ratio (SNR) and 32-bit/384kHz audio support.
Because the CX31993 uses a charge pump to create a negative rail, it generates a true ground-biased output. Cx31993 Datasheet Fix
Specific impacts for CX31993-class devices Assuming CX31993 is a multimedia/communication IC (video/audio front end, codec, or RF IF chip), the above issues can manifest as:
The standard documentation often underemphasizes the sensitivity of the analog power rail (AVDD). Insufficient filtering causes USB bus noise to bleed into the audio output.
This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later. Use the following verified register bitmasks for tracking
The Cx31993 is an incredibly capable audio DAC when configured correctly. By implementing proper USB-C CC termination resistors, stabilizing the AVDD rail with low-ESR capacitors, and isolating your analog and digital grounds, you can bypass the omissions in the factory documentation. To help tailor this guide, please let me know:
Crosstalk occurs when the return current of one audio channel interferes with the other.
3. The "Datasheet Fixes": Hardware Modifications and Circuit Optimizations It is widely used in portable headphone dongles,
The CX31993 utilizes an internal digital volume control matrix that maps poorly to standard Android ALSA drivers, resulting in a massive volume jump between steps 2 and 3.
What specific are you experiencing?
A frequent issue with cheap Cx31993 dongles is that they work perfectly via a USB-A adapter but fail to register when plugged directly into a USB-C to USB-C cable.
The official Conexant engineering brief provides a bare-minimum reference design. It often omits the robust protection and filtration networks required for real-world USB environments. Below are the critical engineering modifications required to correct these design oversights.