Low-Voltage Power Detect Circuit With Switched Bandgap PSRR Control
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Solution Overview
Problem
High precision, low voltage power detect circuits face challenges in operating effectively under extremely low supply voltages while maintaining high power supply rejection ratio (PSRR) in advanced CMOS processes, particularly in applications like power-on-reset circuits and voltage monitors for integrated circuits (ICs).
Innovation Solution
A power detect circuit design that includes a voltage multiplier to generate a higher supply voltage, a voltage regulator, a bandgap circuit with current mirror and chopping circuitry, and a comparator, along with a voltage monitor to manage switches and ensure the bandgap circuit receives the appropriate supply voltage, enhancing PSRR and startup/recovery times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power detect circuit operates under extremely low supply voltages to improve power efficiency, then power consumption is reduced, but the power supply rejection ratio (PSRR) deteriorates and measurement precision decreases
Solution Approach 1:
The power detect circuit is segmented into multiple operational modes: a first mode for very low supply voltages using a voltage multiplier and first bandgap circuit, and a second mode for higher supply voltages using a voltage regulator and second bandgap circuit. This segmentation allows the circuit to optimize PSRR for each voltage range independently, maintaining high measurement precision while operating efficiently at low voltages.
Solution Approach 2:
The circuit dynamically changes operational parameters based on supply voltage level. A voltage monitor detects the supply voltage and controls switches to transition between operational modes, changing the reference voltage generation mechanism (first bandgap at 0.4-1.0V vs. second bandgap at higher voltages) to maintain optimal PSRR across different voltage conditions.
2Measurement precision
If a voltage multiplier is used to generate higher supply voltage for the bandgap circuit to improve PSRR, then power supply rejection ratio is enhanced, but device complexity increases
Solution Approach 1:
The circuit employs dynamic switching between different operational configurations based on supply voltage conditions. Switches controlled by a voltage monitor enable the circuit to adapt its structure - using the voltage multiplier only when necessary at low voltages, and transitioning to a simpler regulator-based configuration when supply voltage is sufficient, thereby managing complexity dynamically rather than statically.
Solution Approach 2:
The voltage multiplier functionality is extracted as a separate, optional component that is only activated when supply voltage falls below a threshold. This allows the main circuit to operate in a simpler mode during normal conditions, while the voltage multiplier serves as a specialized subsystem for low-voltage operation, reducing overall complexity by making the enhancement conditional rather than permanent.
3Measurement precision
If multiple bandgap circuits are implemented to cover different voltage ranges, then measurement precision is maintained across all voltages, but device complexity and power consumption increase
Solution Approach 1:
The reference voltage generation is segmented into two separate bandgap circuits, each optimized for specific voltage ranges. The first bandgap circuit handles very low voltages (0.4-1.0V) while the second handles higher voltages, allowing each circuit to be independently optimized for its operating range, maintaining measurement precision without requiring both circuits to operate simultaneously at full power.
Solution Approach 2:
The circuit dynamically selects which bandgap circuit to use based on supply voltage conditions. Switches controlled by the voltage monitor enable only the appropriate bandgap circuit to be active at any given time, reducing power consumption by avoiding simultaneous operation of both circuits while maintaining measurement precision across the full voltage range through selective activation.
Data Source
AI summary
A power detect circuit is disclosed. A power detect circuit includes a voltage multiplier that receives an external supply voltage and generates a second supply voltage that is greater than the former. A voltage regulator is coupled to receive the second supply voltage and outputs a regulated supply voltage. A bandgap circuit is coupled to receive the second supply voltage when a first switch is closed, and the regulated supply voltage when a second switch is closed. The bandgap circuit generates a reference voltage for the voltage regulator, as well as one or more output voltages. A comparator circuit is coupled to receive the one or more output voltages from the bandgap circuit, and may compare these one or more output voltages to the regulated supply voltage.