While the full NDA-protected datasheet is restricted, publicly available specifications and reverse-engineered data reveal the following key parameters:
The datasheet figures reveal a limitation: the CX31993 is optimized for IEMs (In-Ear Monitors) and low-impedance headphones. With a max output of 1.2Vrms, it struggles to drive high-impedance studio headphones (e.g., Sennheiser HD600 series at 300Ω). On a 300Ω load, the power output drops to roughly 0.5mW, resulting in low volume.
In the wake of the smartphone headphone jack removal and the shift toward ultra-thin laptops, the humble USB-C to 3.5mm adapter has become an essential daily driver for millions of users. At the heart of many of the best-performing, budget-friendly dongles lies a specific integrated circuit: the Conexant CX31993. cx31993 datasheet
For engineers and audio enthusiasts searching for the "CX31993 datasheet," the goal is usually the same: to verify power output (mW), Total Harmonic Distortion (THD+N), and compatibility with high-impedance headphones. While the full manufacturer datasheet is often restricted under NDA (Non-Disclosure Agreement) with Synaptics (which acquired Conexant), this article aggregates the publicly available technical specifications, electrical characteristics, and circuit design implications of the CX31993.
A reference implementation for a USB-C dongle: Output Power:
Since the official PDF is restricted, the hardware community has mapped the CX31993 in USB-C dongles (like the Ugreen 50744 and CableCreation). The chip is usually a 3mm x 3mm QFN.
Pin 1: VBUS (5V input) Pin 2: GND (Power ground) Pin 3: HP_DET (Headphone detection – detects 3.5mm insertion) Pin 4: MIC_BIAS (Provides 1.8V for electret microphone) Pin 5: MIC_IN (Mono microphone input from TRRS sleeve) Pin 6: AGND (Analog ground) Pin 7: HPOUT_R (Right channel output) Pin 8: HPOUT_L (Left channel output) Pin 9: VCOM (Common mode voltage reference – decoupling cap required) Pin 10: DVDD (Digital core voltage – 1.2V regulated internally) Pin 11: USB_DM (USB Data Minus) Pin 12: USB_DP (USB Data Plus) Pin 13: XTAL_IN (24MHz crystal input) Pin 14: XTAL_OUT (24MHz crystal output) Pin 15: RST_N (Reset – active low) Pin 16: VDDIO (I/O voltage – 3.3V) ADC (for microphone):
Design Note: Pins 13 & 14 are critical. The CX31993 requires a precise 24MHz crystal oscillator with ±50ppm tolerance. Using a ceramic resonator instead will cause jitter and sample rate mismatch.