The Study Of Key Technologies Of The Digitali/F Converter

I/F converter, i.e. the current-frequency converter, is the device or equipment which converts the input current signal into the output frequency signal in accordance with a linear proportional relationship. In this paper, digital I/F converter with non-linearity of less than5×10-5and high-performance has been designed based on24-bit high-performance A/D converter and digital signal controller.First, the bipolar input current signal through the front-end signal conditioning circuit is converted to the voltage signal which can be identified by the A/D converter (including polarity and size); and the voltage signal is converted to digital by the A/D converter; the digital filter is designed for the sampling signal to reduce the noise component of the useful signal; then according to linear proportional relationship, the size of the output frequency signal is calculated; finally, the calculated frequency signals are output by the PWM or TMR’s output pin of controller, according to the digital frequency synthesis algorithm.This paper studies the key technologies of digital I/F converter, such as the front-end signal conditioning circuits, digital filtering of A/D sampling values, variable gain nonlinearity compensation and digital frequency synthesis algorithm. Using the ADuC847microcontroller of ADI and the MC56F8037digital signal controller of Freescale, digital I/F converter was designed to meet the desired performance indicators. ADuC847completes the A/D conversion for an analog voltage signal which is the outputs of front-end signal conditioning circuit, and variable gain nonlinear compensation for ADC on chip. MC56F8037realizes the digital filtering for A/D sampling values, calculates the output frequency value, completes the digital frequency synthesis and outputs the frequency signals of positive or negative channel. The positive and negative of frequency signals is that positive or negative frequency signal is output by two different pins.Finally, the paper summarizes the hardware and software anti-jamming measures of digital I/F converter involved in the design process.