Monolithic Capacitive Accelerometer Readout Circuit If Variable Pwm And Design

Microsilicon sensors are the tendency of the development of sensors. With the development of CMOS technology, Micro-Electro-Mechanical Systems (MEMS) have become more and more attractive. This paper presents a new capacitive accelerator readout circuit used pulse width modulated (PWM) in single chip.A new PWM circuit is presented in this paper, which is kept the pulse width constant but the pulse cycle adjusted with the modulated signal, so that the duty cycle is changed with the modulated signal. On the contrary, in conventional PWM's the pulse cycle is kept constant, but the pulse width is adjusted with the modulated signal. PWM has a numbers of applications ranging from industrial control to switch power.In this paper, some methods to test the tiny capacitor are introduced, and the feasibility of that using PWM to test the capacitive accelerator is analyzed. The main think is that used capacitive accelerator composed an oscillator, which outputs a frequency adjusted pulse which is sensitive to the change of capacitor. Then the pulse is modulated by PWM. After the modulated signal through a low pass filter, we can get the change of the frequency that related to the capacitor. Because the capacitor changes with the acceleration, the acceleration is got.The whole PWM circuit contains two subcircuit, the front-end is PWM module that make up of the counter that based on nine MOSFET True-Single-Phase-Clock D flip-flop; the back-end is demodulated module, which is consist of a three order Chebyshev low-pass filter used trans-conductor capacitor. All the subcircuits are simulated. At last, an approving simulated result of the whole circuit is given too.With the development toward sub-micron and deep sub-micron technologies, CMOS will have extremely wide market prospects, because its low cost and easy of implementation. Hence all the simulation of this paper uses the CSMC 0.6μm standard CMOS process.