PCM2702 Based USB Sound Card

A fully functional USB sound card has been designed based on a great IC PCM2702 as the core of this construction that contains 16-bit stereo digital to analog converter with USB interface.

The sound card can be powered from USB port and holds one stereo output. Since the device is plug and play, there is no need to install any driver for Windows XP and Windows Vista since it has the drivers inside the device.

Only few additional parts are needed by PCM2702 to work. The USB port directly powers the sound card using jumper W1 or it can be powered using an external power supply using jumper W3. There are two power supplies needed by PCM2702 for the 3.3V and 5V. A fixed voltage output LDO TPS76733Q is used for the 3.3V IO2 while an adjustable voltage LDO TPS76701Q is used for the 5V IO3. Both LDO are produced by TI but any similar LDO can be used. To allow LDO good stabilization, the output voltage of IO3 should be set to a little bit lower than input voltage.

The high frequency hum can be reduced by placing the small ferrite beads.