The MC145482 is a 13bit linear PCM CodecFilter with 2s complement data format, and is offered in 20pin SOG and SSOP packages. This device performs the voice digitization and reconstruction as well as the band limiting and smoothing required for the voice coding in digital communication systems. This device is designed to operate in both synchronous and asynchronous applications and contains an onchip precision reference voltage. This device has an input operational amplifier whose output is the input to the encoder section. The encoder section immediately lowpass filters the analog signal with an active RC filter to eliminate very high frequency noise from being modulated down to the passband by the switched capacitor filter. From the active RC filter, the analog signal is converted to a differential signal. From this point, all analog signal processing is done differentially. This allows processing of an analog signal that is twice the amplitude allowed by a singleended design, which reduces the significance of noise to both the inverted and noninverted signal paths. Another advantage of this differential design is that noise injected via the power supplies is a commonmode signal that is cancelled when the inverted and noninverted signals are recombined. This dramatically improves the power supply rejection ratio. After the differential converter, a differential switched capacitor filter band passes the analog signal from 200 Hz to 3400 Hz before the signal is digitized by the differential 13bit linear A/D converter. The digital output is 2s complement format.