Feedback pins. These must be routed back from the headphone jack terminals to provide active DC offset correction and load sensing.
If you applied these datasheet fixes and still face issues, check the following hardware bugs: The DAC is recognized by the computer but outputs no sound
Before diving into hardware fixes, you must understand what the Cx31993 chip is capable of achieving under optimal conditions. Up to 32-bit / 384kHz PCM.
The CX31993 features an internal low-dropout (LDO) regulator. It requires a dedicated 1.0µF to 2.2µF decoupling capacitor to ground to stabilize the core logic. USB Interface
The reference design sometimes omits the mandatory 5.1kΩ pull-down resistors on the Configuration Channel ( CC1 and CC2 ) lines of the physical USB-C port. Without these, modern host devices (like iPads, MacBooks, or newer Android phones) will not supply power ( VBUS ).
The internal analog-to-digital reference voltage (VREF) pin is incredibly sensitive to ripple voltage. Standard datasheets recommend a single 1µF capacitor. In noisy USB environments, this is insufficient.
Analog and Digital grounds. These must be tied together at a single point (star ground) right under the IC using a ferrite bead or a 0-ohm resistor to prevent ground loops. 2. USB Interface Lines
When designing a new revision of a Cx31993 circuit board, adhere to these layout rules to permanently avoid the need for post-production fixes: Requirement / Specification Minimum 4-layer PCB recommended Separates digital signals from analog audio routes Grounding Strategy Split AGND and DGND, joined at a single star point
Here are the typical issues reported by users and the solutions derived from the device's datasheet and community knowledge.
VBUS (5V) from USB-C has a 10µF bulk capacitor and a ferrite bead filter.
