Design Of PFD And CP In PLL

According to incomplete statistics, more than 80% information people abtain is from the visual organ. With the development of semiconduct technology, image sensor plays the role of human eyes in visual information acquisition, transfer and extention. As a highly integrated and low power image sensor, CMOS Image Sensor is gradually replacingCCD Image Sensor as the mainstream device. CP PLL circuit with its low power, high speed, low jitter and low cost advantages, has been widely used in the CIS. PFD phase (Phase Frequency Detector, PFD) and charge pump (Charge Pump, CP)are the key modules in CP PLL circuit, the former determines the accuracy and stability of the system, while the latter provides a wide frequency capture range and fast locking capabilities.The project background of PLL synthesizer has been presented first along with the characters of CPPLL. Afterwards, the classifications of the PFD and CP were introduced, followed by the design of performance indicators and the dominated issues in detail. As all the basic knowledges were exposited, the PFD structure of TSPC (true single phase clock, TSPC) dynamic D flip-flops and the CP structure with a wide input scale error amplifier associated with a self-biased CASCODE current mirror have been presented to achieve a high performance. After giving the design size of PFD and CP, the layout designs were presented and optimized in the process of 0.18μm CMOS. In the end,the chip was taped out with a testing results showing that:the PFD has correct logic function, whereas the charge pump current is stable at 100μA in the output range of 0.3V-1.7V, and the current mismatch is less than 0.4μA at output voltage range of 0.4V-1.7V, with total power consumption of 7.2mW at the power supply of 1.8V.As the hot sport of research in the image information field, the development of high performance PFD and CP in the application of Image sensor have a high research value and a promising market prospects, the design of PFD and CP in this paper has been applied into CIS successfully.