The CX31993 lacks an internal heat pad on its QFN package. Unlike desktop DACs that dissipate heat via the PCB ground plane, the CX31993 relies entirely on the dongle’s epoxy casing. If the manufacturer used a 2-layer PCB (most cheap dongles do), heat has nowhere to go. The chip thermally throttles at ~85°C, but the plastic case will burn your fingers long before that.
🔇 Even with extremely sensitive multi-driver IEMs, the background hiss on this chip is practically non-existent. It is exceptionally quiet.
This is often not a hardware failure but a handshake or driver stack issue. Because the CX31993 is strictly "Plug and Play" (UAC 2.0 compliant) and usually does not require custom drivers on Windows or Android, the operating system’s USB Audio driver sometimes "holds" the previous state. The chip's internal controller struggles to renegotiate the USB connection speed without a full power cycle resetting the registers. cx31993 datasheet fix hot
The CX31993 is a high-performance, low-power USB Type-C audio SoC often used in budget "dongle" DACs. Up to 32-bit / 384kHz. Signal-to-Noise Ratio (SNR): 128dB. Dynamic Range: 120dB. Output Power: ~65mW into 32Ω.
The Conexant CX31993 has become a darling in the portable audio world. Found in countless ultra-compact USB-C to 3.5mm dongle DACs (often labeled as "Hi-Res Audio" or "32bit/384kHz"), this chip offers impressive specs for its size and price. It supports PCM up to 384kHz and has a built-in headphone amplifier capable of driving many IEMs and headphones. The CX31993 lacks an internal heat pad on its QFN package
Because the CX31993 uses a QFN package, its primary method of cooling is through the exposed ground pad (ePAD) on the bottom of the chip. Budget dongles often skimp on copper layers to save costs.
The CX31993 datasheet specifies internal Low Dropout (LDO) regulators to step down the 5V USB power to 3.3V and 1.2V for the digital core. Linear regulators dissipate excess voltage entirely as heat. The chip thermally throttles at ~85°C, but the
The QFN-20 package has an exposed thermal pad (pin 21, center). The datasheet mandates: "The thermal pad must be soldered to a ground plane with at least 6 vias to the opposite layer." Most low-cost PCBs have no vias, only a small pad. Heat gets trapped inside the chip.