Current-Comparator Relaxation Oscillator for 10 nA Low-Power Timing
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Solution Overview
Problem
Existing oscillators in portable and battery-operated devices face challenges in minimizing current consumption while being insensitive to temperature and power-supply voltage fluctuations, especially for low energy requirements and weak current sources.
Innovation Solution
The proposed oscillator arrangement employs a current comparator with two current branches, utilizing a current mirror and a control unit with a multivibrator to manage charging and discharging currents, reducing the number of current branches and incorporating a reference voltage source proportional to absolute temperature for temperature compensation, thereby minimizing current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional oscillators are used in portable devices, then oscillation function is achieved, but current consumption is too high
Solution Approach 1:
The patent merges the reference voltage generation function into the comparator structure itself by using a current mirror with two current branches. One branch receives the signal from the charge storage device while the other branch generates the temperature-compensated reference voltage. This integration eliminates separate reference voltage circuits that would increase current consumption, achieving ultra-low power operation at 10 nA while maintaining temperature insensitivity through the PTAT reference voltage mechanism.
2Temperature
If temperature compensation is implemented using voltage dividers, then temperature stability is improved, but current consumption increases
Solution Approach 1:
The patent replaces the conventional voltage divider-based temperature compensation mechanism with a current mirror-based system. Instead of using resistive voltage dividers that consume significant current, the invention uses a current mirror with two current branches where one branch generates a reference voltage proportional to absolute temperature (PTAT). This substitution reduces current consumption to ultra-low levels while achieving complete temperature compensation for the oscillation frequency.
3Ease of operation
If multiple current branches are used for charging and discharging, then oscillation control is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal current mirror structure with two current branches that serve multiple functions. The same current mirror circuitry is used for both charging and discharging operations, and for generating both the signal-dependent current and the temperature-compensated reference voltage. This multi-functional design simplifies the overall device complexity while maintaining precise oscillation control through the comparator that switches between charging and discharging phases.
Data Source
AI summary
An oscillator arrangement is specified, in which a relaxation oscillator is refined to the extent that the comparator (2) to be used for comparing the voltage across a charge storage device (1) with a switching threshold (VTH) is a current comparator with two current branches (5, 6). One of these two current branches is used in the present case for guiding a charging or discharging current of the charge storage device (1). In this way, a current branch is eliminated, so that the proposed principle is preferably suitable for so-called ultra low power applications.