Reference Voltage Generating Unit for Stable Power-On Reset
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Solution Overview
Problem
The variability in trimming codes stored in nonvolatile memory when the power source is activated leads to significant variations in the reference voltage generated by semiconductor devices, affecting the timing of reset release in power-on reset circuits, which can result in unstable operation.
Innovation Solution
A semiconductor device comprising a reference voltage generating unit that produces two voltages: one adjusted by trimming data and another independent of it, with a nonvolatile memory operating based on the stable voltage to store trimming data, and a power-on reset circuit that switches logic levels based on a constant multiple of the stable reference voltage, ensuring consistent operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If trimming data is stored in nonvolatile memory and used to adjust reference voltage, then manufacturing precision is improved, but reliability deteriorates due to variability when power source is activated
Solution Approach 1:
The reference voltage generating unit is divided into two independent parts: one that generates reference voltage adjusted by trimming data, and another that generates reference voltage independent of trimming data. This segmentation allows each part to serve specific functions without interference, resolving the contradiction between precision and reliability.
Solution Approach 2:
A power-on reset circuit is introduced as an intermediary component that controls the timing of trimming data reading. By using this mediator, the system ensures that trimming data is only read after the power source voltage stabilizes, preventing variability issues while maintaining precision benefits.
2Ease of operation
If trimming code is read from nonvolatile memory at power-on, then ease of operation is improved, but manufacturing precision deteriorates due to indefinite code values
Solution Approach 1:
The power-on reset circuit performs preliminary action by detecting power source voltage stabilization before allowing trimming data to be read from nonvolatile memory. This preliminary check ensures that memory operations occur only under stable conditions, preventing indefinite code values while maintaining fast initialization.
Solution Approach 2:
The system applies preliminary anti-action by preventing the reading of trimming data until the power source voltage reaches a stable state. This preemptive measure counteracts the potential harm of reading indefinite code values, ensuring manufacturing precision is maintained without sacrificing operational ease.
3Manufacturing precision
If reference voltage is adjusted by trimming data, then manufacturing precision is improved, but object-affected harmful factors increase due to sensitivity to power source voltage variations
Solution Approach 1:
The reference voltage generation is segmented into two paths: one path uses trimming data for precision adjustment, while the other path provides a stable baseline reference voltage independent of trimming data. This segmentation isolates the precision function from power source voltage sensitivity, allowing both goals to be achieved simultaneously.
Data Source
AI summary
To prevent the influence of variations in reference voltage until a power source is activated in a semiconductor device including a reference voltage generating circuit that can be adjusted by trimming data.In a semiconductor device, a reference voltage generating unit generates a first reference voltage adjusted in accordance with trimming data and a second reference voltage that does not depend on the trimming data based on an external power source voltage. A nonvolatile memory operates in accordance with a voltage based on the first reference voltage and stores the trimming data. A power-on reset circuit switches logic levels of a reset signal when the external power source voltage reaches a constant multiple of the second reference voltage at the time of activation of power source. A control circuit causes the reference voltage generating unit to read the trimming data stored in the nonvolatile memory in response to the switching of the logic levels of the reset signal.