Supply Voltage Detection Circuit With Constant-Current Clamping
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Solution Overview
Problem
Conventional supply voltage detecting circuits face challenges in achieving high accuracy, low temperature drift, and low power consumption due to variations in threshold voltage and the need for external signals for resetting, leading to incorrect low-voltage detection and increased power consumption.
Innovation Solution
A supply voltage detecting circuit incorporating a voltage detection circuit and a current clamping circuit, where the current clamping circuit provides a constant current when the supply voltage is above a set level, reducing power consumption and using a base-emitter voltage difference to generate a bias voltage for accurate detection, minimizing temperature drift and eliminating the need for external resetting signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bandgap voltage generator is used to generate reference voltage for accurate supply voltage detection, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing threshold voltage compensation values in a lookup table during the chip manufacturing process. The compensation value corresponds to different threshold voltage corners (FF, FS, SF, SS), allowing the circuit to quickly retrieve and apply the appropriate compensation without real-time calculation, thus maintaining high detection accuracy while minimizing power consumption.
Solution Approach 2:
The patent changes the parameter of threshold voltage compensation by dynamically selecting different compensation values based on the detected threshold voltage corner. The compensation value is adjusted according to the specific MOS transistor threshold voltage characteristics, enabling accurate supply voltage detection across different process corners without requiring a power-hungry bandgap voltage generator.
2Device complexity
If threshold voltage variation in MOS transistors is not compensated, then device complexity is reduced, but measurement precision deteriorates due to ±20% to 40% threshold voltage variation
Solution Approach 1:
The patent uses copying by creating a simplified compensation mechanism that copies the threshold voltage compensation strategy from complex bandgap references. Instead of implementing a full bandgap voltage generator, the patent copies only the essential compensation function through lookup table-based threshold voltage compensation, maintaining measurement precision while significantly reducing device complexity.
Solution Approach 2:
The patent applies parameter changes by introducing a compensation value that adjusts the detection threshold based on the MOS transistor's threshold voltage corner. This compensation parameter is selected from a lookup table based on the detected threshold voltage characteristics, enabling accurate detection without complex circuit structures.
3Ease of operation
If external resetting signals are required to activate the supply voltage detecting circuit, then ease of operation is reduced, but manufacturing precision can be maintained
Solution Approach 1:
The patent applies self-service by enabling the supply voltage detecting circuit to automatically activate and compensate for threshold voltage effects without requiring external resetting signals. The circuit uses its own internal detection mechanisms to identify the threshold voltage corner and retrieve the appropriate compensation value from the lookup table, making the system self-sufficient and easier to operate while maintaining manufacturing precision.
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 high accuracy, low temperature drift, and reduced power consumption by maintaining operation with a constant current and using a bias voltage generated from base-emitter voltage differences, allowing the circuit to function without external activation or resetting signals.
Implementation Method 1
compare the sensing voltage with the reference voltage generated by the bandgap voltage generator to determine whether to make the circuit system operate in the low voltage working mode or start to enter the normal working mode
Implementation Method 2
using a base-emitter voltage difference to generate a bias voltage for accurate detection, minimizing temperature drift
Data Source
AI summary
A supply voltage detecting circuit has a voltage detection circuit and a current clamping circuit. The voltage detection circuit receives and detects a supply voltage and is used to detect to generate a low-voltage detection signal. When the supply voltage is lower than a set level, the low voltage detection signal output by the voltage detection circuit turns off the current clamping circuit, and a transistor current flowing through the voltage detection circuit is proportional to the supply voltage; and when the supply voltage is higher than or equal to the set level, the low voltage detection signal output by the voltage detection circuit turns on the current clamping circuit, and the current clamping circuit provides a constant current to maintain the operation of the voltage detection circuit, wherein the transistor current flowing through the voltage detection circuit is proportional to the constant current.