The AK4555 is a low voltage 20bit A/D & D/A converter for portable digital audio system. In the AK4555, the loss of accuracy form clock jitter is also improved by using SCF techniques for on-chip post filter. Analog signal input/output of the AK4555 are single-ended, therefore, any external filters are not required. The AK4555 is suitable for portable digital audio system, as the AK4555 is low power dissipation and a small package.