An 18b Oversampling A/D Converter for Digital Audio

IN RECEN'T YEARS, there has bceii significant progress in thc I'ii~ld o f consumer digital audio. Recently, L)AT players c.inplov I6b A-to-U and D-to-A conversion. In thc professional audio market, thrrtis a need for higher rrsolution conversion so that 16b quality can be maintained when man); tracks are mixed togetlirr. This paper will present a monolithic J6b A/D converter that achicvcs 105dl3 SjU and 0.00370 TIiDW by using oversainpling and drcimation trchniques. Thc convrrtrr consists of a lront (-rid f,Sl and two dccimator/filtcr 1Cs t o reduce thc sampling rate . Thy lront rnd contains a 4b quantiwr and runs at Ilz. whiclr is 1211 tirnrh fastc,r than thr. final sampling rate of 481i11z. When combined with the two dccimator/filtcr ICs, a compli,tc* I8b A/U converter IS rcalizrd. t'igurv I shows the overall block diagram of thc converter. l h c front (.rid IS1 is a no opvralional amplifiers, a %b 1 an cxtrrrid resistor net work w!hich forms the loop D j A convcrtt>r. The loop f'iltrr c o n s i s t s of a I.th-order I'iltcr composed of thrixiactivr integrators wit t i r r a l zi'roi: and a pa