Digital potentiometer, also known as digitally programmable resistor, is a new type of integrated circuit for CMOS digital and analog mixed signal processing that replaces traditional mechanical potentiometers (analog potentiometers). The digital potentiometer is controlled by a digital input and produces an analog output. Depending on the digital potentiometer, the maximum tap current can be from a few hundred microamperes to a few milliamperes.
◆ Produced by the principle of sensor, with good linearity, precision and temperature stability.
◆ Using software to realize the function, it can be customized according to the change of use requirements.
◆ The working mode is non-contact, avoiding the wear of traditional potentiometer, long life and high reliability.
◆ Due to the elimination of the brush substrate in the traditional potentiometer, the effective stroke reaches 360 °, realizing measurement without blind spots.
◆ There are many types of output signals (0-5V / 0-10V / 4-20mA / serial digital signal output), which is convenient for signal collection and processing.
◆ The effective stroke and output signal can be changed through software to meet various special requirements.
◆ Wide range of application and flexible use.
The digital potentiometer eliminates the resistance substrate and brush, and is a semiconductor integrated circuit. Its advantages are: high adjustment accuracy; no noise, extremely long working life; no mechanical wear; used in automatic control systems to achieve accurate measurement of angular position, and can also use the characteristics of the output feedback signal linearly proportional to the angle change , Through the drive shaft to achieve output adjustment function.
Digital potentiometers generally have a bus interface, which can be programmed through a single-chip microcomputer or logic circuit. It is suitable for forming various programmable analog devices, such as programmable gain amplifiers, programmable filters, programmable linear regulated power supplies and tone / volume control circuits, which truly “put analog devices on the bus” The new design concept of the analog function block of the bus control system).
Because digital potentiometers can replace mechanical potentiometers, the two have similarities in principle. The digital potentiometer belongs to the integrated three-terminal variable resistance device and its equivalent circuit. When the digital potentiometer is used as a voltage divider, its high end, low end, and sliding end are respectively represented by VH, VL, and VW; when used as an adjustable resistor, they are represented by RH, RL, and RW, respectively.
The digital control part of the digital potentiometer includes 4 digital circuit modules including up-down counter, decoding circuit, preservation and recovery control circuit and non-volatile memory. The in / out counters can be used to realize up / down counting under the control of input pulses and control signals. The counter provides the accumulated data directly to the decoding circuit control switch array, and also transfers the data to the internal memory. save. When the external count pulse signal stops or the chip select signal is invalid, only one output terminal of the decoding circuit is valid, so only one MOS tube is selected to be turned on.
The memory of the digital control part is a kind of non-volatile memory after power-off. When the circuit is powered off and then powered on again, the original control data is still stored in the digital potentiometer. The resistance value from the middle tap to the two ends is still The result of the last adjustment. Therefore, the use effect of digital potentiometer and mechanical potentiometer is basically the same. However, since the switch works in a “connect before disconnect” mode, the resistance value of the digital potentiometer may have a certain difference from the expected value during the input count is valid, and the expected value can only be reached after the adjustment is completed.
Digital potentiometers are being rapidly promoted at home and abroad, and are widely used in testing instruments, PCs, mobile phones, household appliances, modern office equipment, industrial control, medical equipment and other fields. For example: refrigerators, programmable controllers, power supplies, power meters, automatic detection equipment, fiber optic networks, LCD screen adjustment, voltage control, replacing mechanical potentiometers, matching linear impedance, adjusting VCOM settings.
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