Abstract: Step-up/step-down DC-DC converter converts 2V to 16V input to a 9V output at up 500mA. The circuit employs the MAX761 internal-switch boost DC-DC converter and a Zetex FZT749 PNP transistor. The topology is boost followed by LDO. The circuit shown in Figure 1 is a low-cost step-up/step-down DC-DC converter. By definition, its input voltage can range above and below the regulated output voltage. The circuit includes a simple switch-mode boost converter (IC1) that contains a comparator, normally used to detect low battery voltage. In this example, the comparator controls an external, low-cost pnp transistor operating as a linear regulator. Figure 1. This step-up/step-down converter maintains a regulated output (set to 9V for the R3/R4 values shown) as the input voltage varies between 2V and 16V. IC1 steps up VIN (2V min) to the level of VX as determined by the jumper block JU1. A 2-3 jumper selects the internal divider, producing VX = 12V, and a 2-1 jumper selects feedback resistors R1 and R2, producing VX = 1.5V(R1 + R2)/R2. VX should be set 1V to 2V above the desired output voltage. Linear regulator Q1 steps down VX to an output level set by R3 and R4: VOUT = 1.5V(R3 + R4)/R4 where VX>VOUT. When VIN>VX, the switching regulator stops and the linear regulator alone controls VOUT. C6 reduces output ripple. This circuit allows a wide range of input and output voltages, and delivers output currents up to 500mA (Figure 2). Figure 2. For VOUT = 9V, the maximum output current in Figure 1 varies with input voltage, as shown. A similar idea appeared in the 7/16/98 issue of Electronic Design. We Want Your Feedback! 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 1810: Jul 16, 1998 MAX761 12V/15V 또는 전압 조정 가능, 고효율, Low-IQ, 스텝 업 DC-DC 컨버터 전체 데이터 시트 (PDF, 136kB) 무료 샘플   다운로드, PDF 형식 (33kB)  AN1810, AN 1810, APP1810, Appnote1810, Appnote 1810