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. 関連製品   APP 1802: Dec 05, 2002 MAX5161 低電力ディジタルポテンショメータ フルデータシート (PDF, 160kB) 無料 サンプル MAX6308 5ピン、マルチ入力、プログラマブルリセットIC フルデータシート (PDF, 128kB) 無料 サンプル MAX6817 ±15kV ESD保護、シングル/デュアル/オクタル(8回路)、CMOSスイッチデバウンサ フルデータシート (PDF, 200kB) 無料 サンプル 自動アップデート お客様が関心のある分野でアプリケーションノートが新規に掲載された際に自動通知Eメールの受信を希望する場合は、EE-Mail™にご登録ください。 We Want Your Feedback! フィードバックをお寄せください。 内容に満足されましたか、あるいは満足されていませんか？もっと良いページにできると思いますか？あるいは、単なるコメントでも結構です。フィードバックをお待ちしています。—マキシムはお客様からいただく訂正、提案を元に改善していきます。 このページを評価し、フィードバックを送信する。   ダウンロード、PDFフォーマット(32kB)  AN1802, AN 1802, APP1802, Appnote1802, Appnote 1802