An ultra-low power temperature compensated sleep mode timer has been developed at the University of Michigan. Energy-constrained systems such as wireless sensor nodes typically have an active mode and a sleep mode. In sleep mode, a timer is required to keep track of when to wake up the system. However, such a timer should ideally have ultra-low power requirements, and also exhibit temperature compensation.
The ultra-low power temperature compensated sleep mode timer developed at the University of Michigan achieves the aforementioned desired features. The key idea of the design is to bias each stage of an oscillator circuit with a linear complimentary-to-ambient-temperature (CTAT) voltage produced by a stack of diode connected transistors. As a result, bias voltage decreases linearly as temperature increases. Using a combination of NMOS transistors for supply voltage regulation, and PMOS transistors as threshold voltage devices, a higher temperature coefficient can be achieved. The higher temperature coefficient translates into temperature compensation of oscillator frequency. Overall, the timer comprises a set of stages that each oscillate at low frequency and demonstrate low power requirements.
- Sensors for oil-borehole exploration
- Low overhead
- Low area
- High efficiency