A High-Precision Programmable Delay Circuit with Ultra-Wide Range ( μs-Tens of Seconds)

In this paper, a novel programmable delay circuit with ultra-wide delay range and high precision is proposed for automatic control systems. This circuit is based on counting the specified number of periods of relaxation oscillator (ROSC) to generate the precise delay. To achieve the ultra-wide delay, wide-range ROSC and programmable digital control cell are adopted. Utilizing good frequency linearity of ROSC, delay with high precision is realized. A detailed theoretical analysis of delay error is derived. Compared with the conventional method, such as the timer of field programmable gate array (FPGA), this circuit features low power consumption, compact area and vibration immunity. Implemented in 0.18-μm CMOS process, a prototype of the proposed delay circuit occupies an area of 1.27×0.46 mm and consumes 211 μA current at 800KωRSET. With a supply voltage range of 2.25-5.5V, the measured delay range is from 2.0417 μs to 31.7366s, and the normalized delay error variation with VDD is 0.18%. In the delay intervals of 1.9-15.2 μs, 15.2-972.8 μs and beyond 972.8 μs, the measured values of normalized delay error without fixed error are less than 4.3%, 1% and 0.75%, respectively. Besides, the method to adjust the delay time is effortless, which is easy to use.