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Digitally Controlled Sine-Wave Generator

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描述

A similar version of this article appeared in the May 15, 2003 issue of EDN magazine.

The circuit of Figure 1 produces an accurate variable-frequency sine wave for use as a general-purpose reference signal. It includes an 8th-order elliptic, switched-capacitor lowpass filter (IC3) that is clocked with a 100kHz square wave generated by microcontroller IC2. (Any other convenient squarewave source is also acceptable.) The microcontroller is clocked by a 10MHz oscillator module. A voltage supervisor (IC1) ensures correct operation in the event of a power failure. IC3 sets the filter's cutoff frequency at 1/100 the clock frequency.

Figure 1. By removing harmonics from a square wave, this circuit generates an accurate and adjustable sine-wave output.

Figure 1. By removing harmonics from a square wave, this circuit generates an accurate and adjustable sine-wave output.

The 8th-order elliptic filter's sharp rolloff sharply reduces the harmonic amplitudes in a 1kHz square-wave input, thereby producing a near-perfect 1kHz sine wave at its output. Using divider-chain logic or a processor, you can then create a digitally adjustable sine-wave source by adjusting the clock and input frequencies while maintaining a ratio of 100:1 between them.

To prevent clipping at the positive and negative peaks, attenuate the input signal and superimpose it on a dc level of VCC/2. The result (for a 5V input) is a 2.25V peak-to-peak output.

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设计,建造,测试

图中的电路板已完全组装并经过测试。

 

细节部分

细节部分

Maxim设备 (2)

器件号 名称 产品线 购买 设计套件和评估模块
MAX7400 八阶、低通、椭圆函数、开关电容滤波器 模拟滤波器 立即购买 Not Available
MAX809 3引脚微处理器复位电路 电路监控、电压监测器及排序器 立即购买 Not Available

Maxim设备 (2)

器件号 产品线
模拟滤波器
八阶、低通、椭圆函数、开关电容滤波器
Not Available
电路监控、电压监测器及排序器
3引脚微处理器复位电路
Not Available

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