As systems grow smaller, it becomes increasingly attractive to replace mechanical potentiometers with smaller and less expensive silicon equivalents (EPOTs). A common interface for such EPOTs consists of a chip select, increment, and Active-Low up/down line. CS activates the device, and on a rising edge of Active-Low INC steps the wiper in a direction indicated by the Active-Low U/D pin. The simple circuit of Figure 1 employs two pushbuttons (one for up and one for down) and a few tiny silicon devices to implement a debounced, ESD-protected EPOT system. Figure 1. These three ICs form a solid-state potentiometer (EPOT). The normally open pushbutton switches feed into an ESD-protected switch debouncer in a SOT23 package (MAX6817) which has internal pullup resistors on the inputs and buffered, non-inverting CMOS outputs. In the absence of a switch closure, the normally open switches hold the MAX6817 outputs high. In turn, that condition ensures a low state for the active-low, push-pull output of the MAX6308; an SC70 reset device with two reset inputs that are independent of the Vcc pin. The reset device must have extra reset inputs rather than a manual reset input, because the glitch-immunity protection of MR inputs is not sufficient to guarantee proper operation. The MAX5161 is a 32-tap, linear-taper EPOT in a SOT23 package, with the standard (Active-Low INC)-Active-Low U/D interface. (The CS input is pulled high internally.) Its tsetup requirement is 50ns, meaning the Acitve-Low U/D signal must be stable for 50ns preceding a rising edge at the Active-Low INC pin. That requirement is met with the delay introduced by transient-filtering circuitry internal to the MAX6308. The delay (shown in Figure 2 as tf) is typically 10µsec to 30µsec. Active-Low INC goes high again only after the reset timeout interval expires. For the MAX6308, that interval (treset) is preset at the factory with a value as short as 1msec. Figure 2. Closing either pushbutton in Figure 1 increments the potentiometer output in a direction indicated by the MAX5161's Active-Low U/D input. A similar version of this article appeared in the September 26, 2002 issue of EDN magazine. 관련 부품   APP 1802: Dec 05, 2002 MAX5161 저전력 디지털 포텐쇼미터 전체 데이터 시트 (PDF, 264kB) 무료 샘플 MAX6308 5핀, 다중 입력, 프로그래밍 가능한 리셋 IC 전체 데이터 시트 (PDF, 124kB) 무료 샘플 MAX6817 ±15kV ESD 보호, 단일/듀얼/옥탈, CMOS 스위치 디바운서 전체 데이터 시트 (PDF, 712kB) 무료 샘플 자동 업데이트 관심 분야의 애플리케이션 노트가 나올 때 자동으로 업데이트를 원하십니까? 그렇다면 EE-Mail™을 신청하십시오. We Want Your Feedback! 의견을 보내주세요! 위 내용이 도움이 되셨나요? 여러분의 의견을 기다립니다 — Maxim은 보내주신 정정이나 제안사항을 반영하고 있습니다. 이 페이지를 평가하고 의견을 보내주십시오.   다운로드, PDF 형식 (32kB)  AN1802, AN 1802, APP1802, Appnote1802, Appnote 1802