When designing a PCB footprint for the CX31993 (typically a 24-pin or 32-pin QFN package), implement the following corrections to bypass datasheet layout errors. Audio Output Inversion Fix
This comprehensive guide serves as an unofficial datasheet fix, addressing the most common hardware implementation errors, missing register documentation, and circuit stability issues. 1. Hardware and Schematic Corrections Cx31993 Datasheet Fix
The Conexant/Synaptics CX31993 is one of the most popular USB-C DAC (Digital-to-Analog Converter) chips on the market. It powers countless budget-friendly audio dongles, offering impressive 32-bit/384kHz audio decoding. However, engineers, DIY hobbyists, and audiophiles frequently encounter integration and performance issues due to errors, omissions, or misinterpretations of the standard CX31993 datasheet. When designing a PCB footprint for the CX31993
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. offering impressive 32-bit/384kHz audio decoding. However
Ensure the MIC_BIAS resistor is set exactly to the capsule's requirements (usually 2.2kΩ to 4.7kΩ connected to the internal bias rail). Place a small ferrite bead or a 10pF to 33pF capacitor between the MIC_IN pin and GND right at the headphone jack to filter out cellular RF interference.
| Incorrect Claim | Correct Information | |----------------|----------------------| | Pin 7 = Analog GND | Pin 7 = (headphone detection, active low) | | Pin 11 = VDDIO | Pin 11 = VOUT_REF (common mode reference for output) | | Pin 14 = MIC bias | Pin 14 = VBUS (USB 5V input – shared with pin 13) | | Supports 32-bit/384 kHz natively | Max 32-bit / 384 kHz but only via USB 2.0 HS; many dongles limit to 96 kHz due to crystal choice |
The DAC connects to the phone, but audio plays through the phone speakers instead of the headphones. The Fix: Ensure the Jack Detection pin ( DETcap D cap E cap T