A 5 V front end chip for a universal voiceband modem

A monolithic circuit designed for a 5-V, 1.2- mu m CMOS process combining a full analog front end with all of the logic functions that, along with one or two external digital signal processor (DSP) chips, can implement all of the voice-band modem standards from 300 to 14400 b/s is described. The analog portion of the circuit occupies 23 kmil/sup 2/ (14.9 mm/sup 2/). Combined with roughly 6000 gates of random logic, I/O pads, and supply buses, the die area totals 63 kmil/sup 2/ (40.7 mm/sup 2/). By being designed for operation with a single 5-V supply, analog circuits may use current high-density processes and migrate to future denser processes. Although analog circuitry will not scale as fast as digital circuitry, performance levels can be maintained. This circuit illustrates the potential for combining high-performance analog functions with complex digital functions on a single VLSI chip, using high-density processes.<
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