Research Of A High Precision Chip For Time Interval Measurement

Time measurement with high precision is becoming more and more important, especially in the scientific, military and industrial fields. In order to improve the precision of time measurement, the tapped delay line method is used to develop the TDC chip. It uses CMOS inverter as the basic delay, which is very small in CMOS technology. The core of this chip is formed of 31 inverters. In order to simplify the usage of the chip, a SPI interface and 64 bytes of registers are integrated inside the chip. The registers are used to store the result of measurement, and with the help of the SPI interface, it becomes very easy to exchange data.After describing the logic diagram of the chip, every module of the chip is introduced in detail, from circuit design to simulation and the results of simulation meet the design destination.The layout of the TDC chip is designed with 0.5μm, three metal and two ploy CMOS technology of Shanghua Company, and is fabricated in Shanghua Company. The package of the chip is 40-DIP. The precision of the chip can reach as high as 300ps, the measurement rang is from 1μs to 2.0ms, and the dead time is less than 1ms.There are also some problems need to solve. Above all, the precision depends on the technology used. In order to develop a method which has little to do with manufacture processing technology, a new method with two delay lines is raised. The basic delays of the two delay lines are not the same, there is a very small difference between the two delay lines, and this difference is used as the smallest step of measurement. This method is introduced in the end.