Application of A/D Converter ADS7822 in High-Speed ​​Data Acquisition

1 Introduction

ADS7822 is a 12-bit serial high-speed A/D converter with a sampling rate of 75kHz and low power consumption (0.54mW at 75kHz and 0.06mW at 7.5kHz).

2 Pin arrangement and functional block diagram:

The pin functions are described as follows:

The pin arrangement of ADS7822 is shown in Figure 1, and the functional block diagram is shown in Figure 2.

3 Electrical Characteristics of ADS7822

The timing of ADS7822 is shown in Figure 3, and its maximum rated electrical parameters and typical electrical parameters are shown in Tables 1 and 2.

4 Design of Transmission Shift Force Data Acquisition System

4.1 System Hardware Design

The system uses Philips' LPC932 microcontroller as the controller, and sends the gearbox shift force data detected by the pull-pressure sensor to the high-speed A/D converter through an amplifier (AD632). The conversion result is sent to the microcontroller and then to a portable PC through a serial port to complete functions such as data display and waveform drawing. [page]

The system block diagram is shown in Figure 4:

4.2 System Programming

As shown in Figure 3, the conversion result of ADS7822 can read 12-bit serial data continuously after 3 DCLOCKs. Each low level of DCLOCK reads one bit of data, and the upper 4 bits D11~D8 are stored in R1, and the lower 8 bits are stored in R2. The program flowchart is shown in Figure 5.

The serial port data transmission program and the corresponding data format conversion code and the software interface implemented by the PC using VC++6.0 are omitted. The AD conversion subroutine list is as follows (CLK is the clock signal, CS is the chip select signal, DAT is the serial data signal; the high 8 bits of data are stored in R1, and the low 4 bits of data are stored in R2):

5 Conclusion

The gearbox shift force intelligent tester based on serial communication designed using the ADS7822A/D converter has been used in industrial sites. Practice has proved that the design has the advantages of simple and reliable structure, high real-time performance and strong anti-interference.