Clocked Schmitt Trigger Comparator for Stable Hysteresis
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Solution Overview
Problem
Existing Schmitt trigger voltage comparators face challenges with unstable threshold voltage ratios due to PVT variations, leading to imprecise hysteresis and continuous DC current consumption, which hinders high precision and accuracy in analog circuits.
Innovation Solution
A Schmitt trigger voltage comparator circuit with a voltage reference input, current sources, a current mirror, and a sequence controller that enables zero DC current consumption by using voltage-controlled current sources and switches to control the current mirror, allowing for variable threshold voltages and precise operation across a wide range of supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional Schmitt trigger circuits are used, then the circuit structure is simple, but the threshold voltage ratios are unstable due to PVT variations leading to imprecise hysteresis
Solution Approach 1:
The patent introduces voltage reference inputs as intermediary elements that mediate the threshold voltage determination process. Instead of relying directly on transistor dimensions and PVT variations, the threshold voltages VT+ and VT- are established through voltage references that are less sensitive to process, voltage, and temperature variations, thereby improving measurement precision while adding controlled complexity
Solution Approach 2:
The patent changes the parameter determination method from fixed transistor dimensions to adjustable voltage references. By making threshold voltages dependent on reference voltages rather than physical dimensions, the system achieves better stability across PVT variations while maintaining circuit functionality
2Measurement precision
If voltage comparators are used to set threshold voltages independently of PVT issues, then measurement precision improves, but DC current consumption increases
Solution Approach 1:
The patent implements periodic action by using clocked switches and sequential operation of voltage-controlled current sources. The circuit operates in discrete phases controlled by clock signals, allowing the current sources to be activated only when needed for comparison operations, thereby achieving high precision threshold setting while reducing continuous DC current consumption to near-zero levels
Solution Approach 2:
The patent introduces dynamic operation through clock-controlled switches and time-varying current sources. The circuit transitions between active comparison phases and low-power standby phases, making the power consumption dynamic rather than static, which enables high precision during operation with ultra-low power consumption when idle
3Adaptability or versatility
If the threshold voltages are extended (VT+ increased to 80% of VDD or VT- reduced to 20% of VDD), then the hysteresis range is increased, but PVT variations cause greater instability
Solution Approach 1:
The patent uses voltage reference inputs as intermediaries to stabilize threshold voltages even when extending the hysteresis range. The references act as stable anchor points that prevent PVT variations from causing instability, allowing VT+ to be increased to 80% of VDD or VT- reduced to 20% of VDD while maintaining reliability through the mediating reference voltages
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves ultra-low power operation with zero static current consumption and high precision, enabling the Schmitt trigger voltage comparator to function effectively across varying supply voltages without glitches, thus overcoming the limitations of traditional Schmitt trigger circuits.
Implementation Method 1
a current source having a first voltage controlled current source connected to the voltage reference input and a second voltage controlled current source connected to a signal input for converting the signal input to a input current and the voltage reference input to a reference current
Implementation Method 2
a current mirror having an input connected to the output of the first voltage controlled current source configured and arranged to invert the direction of the first current and an output of the current mirror connected to the output of the second voltage controlled current source
Data Source
AI summary
A Schmitt trigger voltage comparator circuit is provided including a voltage reference input, a current source having a first voltage controlled current source connected to the voltage reference input and a second voltage controlled current source connected to a signal input for converting the signal input to a input current and the voltage reference input to a reference current, a current mirror having an input connected to the output of the first voltage controlled current source configured and arranged to invert the direction of the first current and an output of the current mirror connected to the output of the second voltage controlled current source, and a sequence controller for generating digital signals to control a first plurality of switches and a second plurality of switches. The first plurality of switches control the first and second voltage controlled current sources and the second plurality of switches control the current mirror.