A data acquisition board, in order to provide flexibility, must be able to accommodate various input voltage ranges. Handling low amplitude signals generally requires an increase in the number of bits of resolution, increasing cost. This application note describes a simple circuit that uses a low cost 10-bit ADC but increases the virtual accuracy to 13-bit. Figure 1. 1 LSB (least significant bit) for an ADC is FSR/2n, where n is the number of bit. FSR (full-scale range) depends from the amplitude of the voltage reference. The input voltage range of the external reference for MAX159, a low power, 108ksps serial ADC available in µMAX®-8 package, is 0 to VDD + 50mV. This large input range permits to accommodate different input range using a scaling technique. The output of a low-cost 3-pin voltage reference is scaled using a digitally programmable voltage divider (MAX5420). This device provides four precision divider ratios of 1, 2, 4, 8. The ratio accuracy span from 0.025% to 0.5% according to the grade (A, B, C). The ratio is selected using the digital inputs D1, D0 as follows: Table 1. DIGITAL INPUTS   D1 D0 DIVIDER RATIO 0 0 1 0 1 2 1 0 4 1 1 8 The reference voltage MAX6141 provides an output voltage of 4.096V. The size of 1 LSB using a divider ratio of 1 will be 4.096/1024 = 4mV. This size change according the following table: Table 2. VREF (V) DIVIDER RATIO LSB (mV) VIRTUAL ACCURACY TO 4.096V FS 4.096 1 4 10-bit 2.048 2 2 11-bit 1.024 4 1 12-bit 0.512 8 0.5 13-bit The effective resolution remains at 10 bits. But compared to a 4.096V FSR system, the virtual accuracy is improved. The size of 1 LSB remains greater than the typical converter noise floor (300µV), also with divider ratio of 8. This ensures that the ADC performances are not limited by the LSB's reduced size. µMAX is a registered trademark of Maxim Integrated Products, Inc. 의견을 보내주세요! 위 내용이 도움이 되셨나요? 여러분의 의견을 기다립니다 — Maxim은 보내주신 정정이나 제안사항을 반영하고 있습니다. 이 페이지를 평가하고 의견을 보내주십시오. 자동 업데이트 관심있는 분야의 애플리케이션 노트가 나올 때 자동으로 업데이트 받고 싶으세요? 그렇다면 EE-Mail™을 신청하십시오. 추가 정보   APP 2013: Jun 20, 2003 MAX159 8핀 µMAX 패키지로 제공되는 +2.7V, 저전력, 2채널, 108ksps, 직렬 10비트 ADC 전체 데이터 시트 (PDF, 248kB) 무료 샘플 MAX5420 디지털 방식으로 프로그래밍 가능한 PGA용 정밀 분배기 전체 데이터 시트 (PDF, 208kB) 무료 샘플   다운로드, PDF 형식 (27kB)  AN2013, AN 2013, APP2013, Appnote2013, Appnote 2013