1. Field of Invention
The present invention pertains to the IC field, more specifically, to a spread spectrum clock generating circuit.
2. Description of Related Art
The spread spectrum clock is applied widely in the integrated circuit system to reduce EMI (Electromagnetic interference).
The general way to obtain a spread spectrum clock is to gate each outputted phase of interpolators in turn, and then reconstruct the clock. However, the conventional method requires a complicated interpolation circuit with high-accuracy, a delay line circuit with all delay cells matching with each other, a multi-phase judging digital filtering circuit, a high-speed digital multiplexer circuit, and so on. As a result, the conventional method has led to a very complicated circuit, which in turn has increased the area and power consumption of circuits. In addition, due to nonlinear attribute of interpolators and delay mismatching of various hierarchies of the delay line circuit, the frequency change of finally obtained spread spectrum clock will be quite non-linear.