What are the application areas of digital potentiometer sensors

　　A digital potentiometer is used to change the attenuation of the signal. R2 is a digital potentiometer and Cwiper is a parasitic capacitor, which is inherent in all digital potentiometers and limits the circuit bandwidth. When the potentiometer swings between 0 and full scale, R1 and R3 are used to limit signal attenuation caused by the digital potentiometer.

　　It should be noted that because the circuit uses an operational amplifier, it can be used for signal amplification and attenuation. Therefore, the methods for increasing bandwidth described below are independent of the selected circuit topology. To calculate the transfer function (VOUT/VIN) of the circuit, potentiometers of different modes can be used in the application field, as shown in Figure 2. In the figure, R2 is divided into R2top and R2bottom, where R2top is the resistance above the contact of the potentiometer, and R2bottom is the resistance below the contact of the potentiometer. Assuming the potentiometer used has an end-to-end resistance of 10 kΩ (ignoring the effect of contact resistance), R2top and R2bottom are ideal transfer functions relative to digital encoding, as shown in Figure 3. The two endpoints and midpoints of the transfer function: R2top=10 kΩ, R2bpttom=0kΩ when the potentiometer is coded as 0; When the potentiometer code is in the middle position, R2top=R2bottom=5 kΩ; When the potentiometer code is in the full scale position, R2top=0 kΩ, R2bottom=10 kΩ.

　　Digital potentiometers can provide logarithmic and linear change functions, logarithmic change of digital potentiometer is often used in Hi-Fi audio equipment volume regulation, can have a nonlinear response characteristics of the human ear to establish a linear change of volume control. Current applications, highly integrated digital potentiometers can provide six independent potentiometers in a single chip, and support multi-channel audio devices such as stereo, surround Dolby systems, etc. For audio equipment, it is necessary to pay attention to the transient process of tap position at each stage, if the tap position is not precisely switched to 0V, the audio signal will have crackling and popping sounds. Fortunately, the new generation of digital potentiometers includes a zero-crossing detection function, such as the DS1802, which ensures that the tap position is changed when a zero-crossing (0V) or 50ms delay is detected, thus reducing audio noise during tap position transients.

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