The CX31993 is a popular, low-cost USB audio codec chip commonly found in portable USB-C to 3.5mm dongle DACs. Users and hardware reviewers have consistently reported a issue—where the chip or the dongle body becomes uncomfortably warm to the touch during normal operation, sometimes leading to audible distortion or shutdown. This report examines the root causes of this thermal problem and the critical missing information in public CX31993 datasheets that would allow engineers to properly fix it.
The CX31993 datasheet (Rev 1.2) specifies a thermal resistance ($R_\theta JA$) of for the QFN-48 package. Based on this specification, system designers calculated that with a maximum power dissipation of 0.5W, the temperature rise above ambient would be a manageable 16°C. cx31993 datasheet fix hot
(5.25V – 3.3V) × 0.088A = 0.17W extra heat. In a QFN package (θja=52°C/W), that's a 9°C rise before considering any audio load. The CX31993 is a popular, low-cost USB audio