Sequential Capacitor Oscillator for Low-Voltage Temperature Compensation
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Solution Overview
Problem
Conventional oscillators require a minimum supply voltage of two threshold voltages plus overhead, which can be limiting in applications with limited voltage supply, such as RFID tags, due to the need for stacking opposing temperature-dependent components to maintain frequency over a temperature range.
Innovation Solution
The oscillator design avoids the need for stacking by varying the charging time of each charging circuit based on transistor threshold voltages, allowing a supply voltage of only one threshold voltage plus an overdrive voltage, using a cascading arrangement of charging circuits with current sources connected to capacitors to achieve temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional oscillators stack opposing temperature-dependent components to maintain frequency over temperature range, then temperature compensation is achieved, but minimum supply voltage increases to two threshold voltages plus overhead
Solution Approach 1:
The oscillator is divided into multiple independent charging circuits (first, second, third charging circuits) that can be triggered in sequence. Each charging circuit operates autonomously to charge its associated capacitor, eliminating the need to stack threshold voltages while maintaining temperature compensation through the coordinated operation of these segmented circuits.
Solution Approach 2:
The charging circuits are arranged to be triggered in a predetermined sequence (first charging circuit triggers second, which triggers third). This preliminary arrangement of trigger relationships allows the system to achieve temperature compensation through timing relationships rather than voltage stacking, reducing the minimum supply voltage requirement.
2Stability of the object's composition
If conventional oscillators use stacked threshold voltage components for temperature compensation, then frequency range is maintained over temperature, but power consumption increases beyond available power in limited voltage applications
Solution Approach 1:
The oscillator uses dynamic triggering relationships where charging circuits are activated in sequence based on the charging state of previous circuits. This dynamic operation allows the system to maintain frequency stability through temporal coordination rather than static voltage stacking, thereby reducing continuous power consumption in limited voltage applications.
3Temperature
If conventional oscillators stack two threshold voltages plus overhead for temperature compensation, then temperature compensation is achieved, but the minimum supply voltage requirement limits operational range in low-voltage applications
Solution Approach 1:
The invention changes the fundamental parameter used for temperature compensation from voltage-based (stacking threshold voltages) to time-based (sequential triggering of charging circuits). By varying the charging time of each circuit according to transistor threshold voltages, the system achieves temperature compensation while operating at lower supply voltages, thereby expanding adaptability to low-voltage applications such as RFID tags.
Data Source
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AI summary
The disclosure relates to a temperature-controlled oscillator. Embodiments disclosed include a temperature-compensated oscillator (100) comprising: a first capacitive charging circuit (101) connected between a supply voltage connection (104) and a common connection (105), comprising a first transistor (106) and a first capacitor (107), the first transistor (106) arranged to switch states when the first capacitor (107) is charged above a threshold voltage of the first transistor (106); a second capacitive charging circuit (102) connected between the supply voltage connection (104) and the common connection (105), comprising a second transistor (109) and a second capacitor (110) arranged to begin discharging when the first transistor (106) switches states, the second transistor (109) arranged to switch states when the second capacitor (110) is discharged below a voltage equal to a supply voltage (VDD) at the supply voltage connection (104) minus a threshold voltage of the second transistor (109); and a third capacitive charging circuit (103) connected between the supply voltage connection (104) and the common connection (105), comprising a third transistor (111) and a third capacitor (112) arranged to begin discharging when the second transistor (109) switches states, the third transistor (111) arranged to switch states when the third capacitor (112) discharges below a threshold voltage of the third transistor (111).