The Design Of An Application-Specific Controller For Pyroelectric Infrared Detector

The principle and structure of pyroelectric infrared detector consisted of pyroelectric infrared sensor, Fresnel lens and an application-specific controller, which is compatible with 0.6μm 1P1M N-well CMOS technology, is introduced in the paper. As a mix-mode chip, the application-specific controller including analog signal and digital signal processing block can be applied to receiving, amplifying, processing, controlling signals of PIR, and offer a wide application in some fields.In analog circuits, by sub-threshold MOSFET, a self-bias current source is presented, which has a high power supply restrain ratio and a Complementary To Absolute Temperature characters. According to negative temperature coefficient of VBE and positive temperature coefficient of VT, a framework of band-gap voltage reference is investigated .The reference offer a source of PIR, distributed three voltage, one as upper-threshold voltage of dual-threshold comparator, the other as lower-threshold voltage of comparator, the other as direct current voltage for second band-pass filter amplifier. First and second band-gap filters amplify small signals and shift direct current voltage, which filter interference and noise by frequency. Then, comparator restrains noise and interference through 700mV voltage window.In digital circuits, an outer RC circuit, combined with inter ring oscillator obtain series of oscillation pulses for system clock and delay clock. System clock provides several synchronism clocks for every sub-circuit. Reset circuit assumes that digital circuits have an initial state and self start. The signal processing circuit for CDS sensor shields infrared signals in the daylight. Zero-cross circuit makes sure output synchronism signals drive silicon control. Then, control and output circuit make certain that all actions of control signals, driver signals and output signals are true.Results from HSPICE simulation and Foundation show that the band-gap voltage reference of IC is 3.126V, has a PSRR of 65dB , an accuracy of 23ppm/℃in [0℃,70℃], and the band-pass filter has an gain of 73dB, whose band-pass frequency is 0.1Hz~10Hz. Comparator's window is 700mV. Time sequence and functions of digital circuits are normal. Every sub-circuit can meet requirement of design.