Abstract: This application note discusses how to build a negative voltage reference without using external resistors or a negative supply by simply combining a simple charge-pump inverter and a positive output voltage reference. Switched-capacitor charge-pumps, which occupy less space than do their inductor-based counterparts, are popular for providing inverted voltages in small hand-held equipment. Combining a switched-capacitor charge-pump with a precision reference, for example, yields an inverted reference from a positive power supply (Figure 1). Unlike the more typical combination of a positive 3-terminal reference and an op-amp inverter, this one delivers accurate inversions without the need for precision resistors and a negative supply. Figure 1. A precision negative reference. The charge-pump inverter (U2) delivers -5V by inverting the output of a 5V precision reference (U1). U1 accepts inputs between 5.2V and 12.5V. Replacing it with a 2.5V reference that accepts 2.7V to 12.5V, as in the MAX6125, produces a -2.5V output. This circuit is very compact. It needs only three surface-mount capacitors, and the ICs occupy tiny SOT23 packages. Output-voltage accuracy depends partly on the initial accuracy of U1. The MAX6150/MAX6125 devices, for example, offer 1% accuracy. To this you must add the error due to the circuit's output voltage drop, which is less than 2mV for 90µA of load current (Figure 2). Figure 2. The load-regulation error of the circuit's output. For a -2.5V output, the circuit draws low quiescent currents that range from 86µA for a 2.7V input to 105µA for a 12.5V input. For -5V outputs, the circuit draws 127µA for 5.2V inputs and 140µA for 12.5V inputs (Figure 3). Figure 3. The circuit's supply current as a function of load current. A similar version of this article appeared in the June 10, 1999 issue of EDN magazine. 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 824: Oct 15, 2001 MAX6125 SOT23, 저가, 저전압강하, 3단자 기준 전압 전체 데이터 시트 (PDF, 728kB) 무료 샘플 MAX6150 SOT23, 저가, 저전압강하, 3단자 기준 전압 전체 데이터 시트 (PDF, 728kB) 무료 샘플   다운로드, PDF 형식 (43kB)  AN824, AN 824, APP824, Appnote824, Appnote 824