Abstract: This article discusses how to improve linearity (due to loading of the wiper) and mid-range frequency response of a digital potentiometer in VCO control applications by adding a single external resistor between H and W. Digital potentiometer ICs (digital pots, or digipots) are convenient for controlling voltage-controlled devices such as VCOs and as an economical alternative for a DAC. In a typical application (Figure 1), a MAX5160 digipot controls the frequency of a VCO, via a 3-wire interface. Figure 1. Adding a resistor (Rext) to this VCO-control circuit minimizes nonlinearity while enhancing the mid-range frequency resolution. The ideal relationship between wiper position and control voltage is a straight line (Figure 2). If the digipot's output resistance is high, however, the loading effect of the VCO input resistance (RIN) tends to make the relationship nonlinear and nonsymmetrical. See the "Without Rext" curve in Figure 2, for which RIN is 0.3 times the digipot's nominal output resistance. Figure 2. These curves for wiper position vs. normalized control voltage in Figure 1 show the effect of adding a simple resistor (RIN) to the circuit. Connecting a resistor (Rext) from VCONTROL to VDD reduces the loading effect of RIN. Making Rext = RIN brings the control curve closer to the ideal, and also makes it symmetrical with regard to the middle position. (See "With Rext" curve.) As an added bonus for VCO control, adding Rext = RIN provides finer resolution around the mid-range frequency, where control is usually the most critical. 相关型号   APP 2095: Jun 02, 2003 MAX5160 低功耗数字电位器 完整的数据资料 (PDF, 264kB) 免费样品 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议   下载，PDF格式 (31kB)  AN2095, AN 2095, APP2095, Appnote2095, Appnote 2095