Power Detect Circuit With Voltage Multiplier for Low-Voltage PSRR
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Solution Overview
Problem
High precision, low voltage power detect circuits in advanced CMOS processes face challenges in operating effectively under extremely low supply voltages while balancing power efficiency and performance, requiring high precision and high power supply rejection ratio (PSRR).
Innovation Solution
A power detect circuit is designed with a voltage multiplier generating a second supply voltage, a voltage regulator producing a regulated supply voltage, and a bandgap circuit that receives either the second or regulated supply voltage based on external voltage levels, utilizing current mirror and chopping circuitry for precise voltage generation and a startup circuit for faster startup and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power detect circuit operates under extremely low supply voltages, then power efficiency is improved, but measurement precision and power supply rejection ratio deteriorate
Solution Approach 1:
The power detect circuit is segmented into multiple operational modes: a first operating mode for extremely low supply voltages using a voltage multiplier and first bandgap circuit, and a second operating mode for higher supply voltages using a voltage regulator and second bandgap circuit. This segmentation allows the circuit to optimize for power efficiency at low voltages while maintaining measurement precision when voltage conditions permit.
Solution Approach 2:
The circuit dynamically changes its operating parameters based on supply voltage levels. A voltage monitor detects the supply voltage and controls switches to transition between operating modes, thereby changing the electrical parameters (voltage multiplication factor, bandgap reference source) to match the current voltage conditions and maintain optimal performance.
2Measurement precision
If a voltage multiplier is used to generate higher supply voltage from low supply voltage, then the bandgap circuit can operate at higher voltage for better precision, but device complexity increases
Solution Approach 1:
The voltage multiplier is dynamically enabled only during startup or when the supply voltage drops below a threshold level. Once the supply voltage stabilizes above the threshold, the voltage multiplier is disabled and the circuit transitions to using the external supply voltage directly. This dynamic operation reduces the time-averaged complexity and power consumption while still providing the precision benefits when needed.
Solution Approach 2:
The voltage multiplier function is extracted as a separate, optional component that can be selectively activated. Rather than always operating the bandgap circuit through a voltage multiplier, the system extracts and uses the external supply voltage directly when conditions permit, simplifying the operational path and reducing device complexity.
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.