The TLV320AIC27 comprises a stereo 18-bit codec (that is, 2 ADCs and 4 DACs), plus a comprehensive analog mixer with four sets of stereo inputs, plus one phone input, two microphone inputs, and one PC-beep input. Additionally, on-chip reference circuits generate the necessary bias voltages for the device, and a bidirectional serial interface allows transfer of control data, DAC, and ADC words to and from the AC'97 controller. The TLV320AIC27 is fully compliant with Revision 2.1 of the AC'97 specification. The TLV320AIC27 has the ADC and DAC functions implemented using oversampled, or sigma-delta, converters and uses on-chip digital filters to convert these one-bit signals to and from the 48 ksps, 16/18-bit PCM words that the AC'97 controller requires. The digital and analog sections of the device are powered separately to optimize performance, and 3.3-V digital and 5-V analog supplies may be used on the same device to further optimize performance. Digital IOs are 5-V tolerant when the analog supplies are 5 V. Therefore, the TLV320AIC27 may be connected to a controller running on 5-V supplies, but use 3.3 V for the digital section of the TLV320AIC27. The TLV320AIC27 is also capable of operating with a 3.3-V supply only (digital and analog).