Composite Resistor Technique for Process and Temperature Compensations of Low Power Ring Oscillators

A process and temperature compensation technique, namely, composite resistor, is adopted for the current controlled oscillators (CCOs). The core is a ring oscillator (RO) and oscillates at 1 MHz at room temperature (25°C) with 50% duty cycle. The temperature compensation is achieved between -20°C and 100°C, and after trimming, the inaccuracies of the output frequencies, 1 MHz, and 0.5 MHz, are below ±1% (3σ) in the same temperature range. As a result, 2 outputs are temperature compensated. The oscillator core consumes 750 nA, the biasing circuit consumes 360 nA, and the complete system consumes 1.256 μA, corresponding to 2 μW at 1.6 V battery voltage. The design, occupying 130 μm × 285 μm die area, is realized in a 0.18 μm Mixed-Signal RF Salicide (1P6M, 1.8V/3.3V) CMOS process.