A 5.8nW, 45ppm/°C On-Chip CMOS Wake-up Timer Using a Constant Charge Subtraction Scheme

Area of Science:

• Integrated Circuit Design
• Low-Power Electronics
• Sensor Technology

Background:

• Conventional RC relaxation oscillators suffer from temperature-dependent comparator delays, limiting their use in precise timing applications.
• Compact wireless sensors require ultra-low power components for extended operational life and miniaturization.

Purpose of the Study:

• To develop an ultra-low power oscillator for reliable wake-up timers in compact wireless sensors.
• To mitigate temperature-induced variations in oscillation period for improved timing accuracy.

Main Methods:

• Implementation of a constant charge subtraction scheme to eliminate comparator delay from the oscillation period.
• Design and fabrication of the oscillator in 0.18µm CMOS technology.

Main Results:

• Achieved ultra-low power consumption of 5.8nW at room temperature.
• Demonstrated excellent temperature stability of 45ppm/°C across a -10°C to 90°C range.
• Exhibited low voltage line sensitivity of 1%.

Conclusions:

• The proposed constant charge subtraction technique effectively removes temperature dependence, enabling stable low-power oscillator operation.
• This design is highly suitable for power-constrained wake-up timer applications in wireless sensor networks.