Data terminal equipment (DTE), such as wireless LAN and wireless local loop, may require data and power on the same cable. A high voltage power source of 24V is required to reduce the voltage drop in the cable. Isolation is provided by the 12V power-supply. For a system with one or two ports, a custom-designed DC-DC converter is more suitable than power modules, or "bricks", since bricks tend to be bulkier and are more expensive. They are more suitable for systems that support more ports, where the power demand is higher. The MAX668 is an excellent choice for the design of a DC-DC step-up converter. The MAX668, a current-mode controller, operates in the PWM mode at medium and heavy loads, providing high-efficiency and low-noise. With power levels greater than 20W, efficiencies of more than 90% are achievable. Figure 1. The circuit of Figure 2 has a 24V output and can deliver current up to 3 amperes, enough to power a system with two ports. A switching frequency of 500kHz was chosen as a compromise between switching loss and the size of inductor L1. Increasing the value of gate resistance R7 will reduce EMI noise, but increase switching loss. A value of 4.7Ω was chosen as a compromise. At an input voltage of 12V, a full load of 3 amperes and an output of 24V, the conversion efficiency was 93%. Figure 2. 関連製品   APP 910: Dec 27, 2001 MAX668 1.8V～28V入力、PWMステップアップコントローラ､µMAXパッケージ フルデータシート (PDF, 216kB) 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(35kB)  AN910, AN 910, APP910, Appnote910, Appnote 910