Microcontroller Low-Voltage Detection Circuit
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Solution Overview
Problem
Conventional microcontrollers reset the real-time clock when the power supply voltage drops, requiring users to repeatedly set time information, which impairs user-friendliness and increases manufacturing costs due to the need for separate external RTC chips.
Innovation Solution
A microcontroller design incorporating two low-voltage detection circuits on a single chip, where the CPU stops operating at a first voltage threshold while the real-time clock continues operating until a lower second voltage threshold is reached, allowing the real-time clock to maintain operation without resetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the microcontroller is designed to reset the whole system when power supply voltage drops to prevent CPU runaway, then system stability is improved, but the real-time clock function is unnecessarily reset requiring users to re-set time information
Solution Approach 1:
The patent segments the voltage detection and reset control by introducing two separate low-voltage detection circuits with different threshold values. The first detection circuit (higher threshold) controls CPU reset, while the second detection circuit (lower threshold) controls real-time clock reset. This segmentation allows differential handling of the CPU and real-time clock during voltage drops, preventing unnecessary resets of the real-time clock while maintaining system stability.
2Use of energy by moving object
If the real-time clock operates at lower voltage than the CPU, then power consumption is reduced, but the real-time clock cannot maintain operation when voltage drops below CPU minimum operation voltage
Solution Approach 1:
The patent implements dynamic voltage threshold management by using two detection circuits with different thresholds. When voltage drops between the two thresholds, the CPU is reset while the real-time clock continues operating. When voltage drops below the lower threshold, both are reset. This dynamic approach allows the real-time clock to operate at lower voltages reliably, maintaining clock function continuity while reducing power consumption.
3Device complexity
If a single chip microcontroller is used, then device complexity is reduced, but the real-time clock cannot operate independently at lower voltages without external RTC chip
Solution Approach 1:
The patent applies local quality by giving different voltage detection thresholds to different functional blocks within the same chip. The first low-voltage detection circuit is optimized for CPU operation voltage, while the second is optimized for real-time clock operation voltage. This allows each component to operate at its optimal voltage range, providing adaptability for different voltage conditions while maintaining single-chip integration and reducing overall device complexity.
Data Source
AI summary
A microcontroller includes a first voltage detector that detects whether a power supply voltage is equal to or lower than a first voltage value to generate a first signal, a second voltage detector that detects whether the power supply voltage is equal to or lower than a second voltage value to generate a second signal, the second voltage value being lower than the first voltage value, a real-time clock that includes a memory and a clock counter responsive to a clock signal, and a Central Processing Unit (CPU) that receives the first signal. The first voltage detector, the second voltage detector, the real-time clock and the CPU are formed on a single chip. The clock counter receives the second signal. The memory stores a first value according to a second signal, and stores a second value according to a setup of time information to the clock counter.