Power-Down Detection Circuit With Boosted Reference Switching
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Solution Overview
Problem
Existing power down detection circuits in flash memory devices face challenges in accurately detecting a drop in supply voltage due to instability in reference voltage generation, leading to potential reset failures when the supply voltage drops below the expected power down detection level.
Innovation Solution
The power down detection circuit incorporates a boost circuit and a switching component that stabilizes the reference voltage generation by switching from the supply voltage to a boosted voltage before the supply voltage reaches the power down detection level, ensuring accurate detection by maintaining the reference voltage within a stable range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the supply voltage VCC drops to the power down detection level, then the comparator should detect the voltage drop and output a reset signal, but the reference voltage VREF generated by the BGR circuit becomes lower than expected and the detection fails
Solution Approach 1:
The patent applies preliminary action by detecting when the supply voltage VCC approaches the power down detection level (using a first detection circuit before the actual power down level), and in advance switching the power supply of the BGR circuit from VCC to a boosted voltage VXX. This preliminary switching ensures that the reference voltage VREF remains stable and at its expected level right when it is most needed for accurate detection, preventing the detection failure that would otherwise occur.
2Device complexity
If the BGR circuit generates reference voltage based on supply voltage VCC, then the circuit structure remains simple, but the reference voltage varies when supply voltage drops causing detection failure
Solution Approach 1:
The patent introduces an intermediary boosted voltage VCC_BGR (generated by a charge pump circuit from the supply voltage VCC) as a mediator to power the BGR circuit. Instead of directly using the unstable supply voltage VCC during voltage drops, the intermediary boosted voltage ensures the BGR circuit receives sufficient and stable power, maintaining reference voltage stability without requiring a completely complex voltage regulation system.
Solution Approach 2:
The patent applies parameter changes by dynamically changing the power supply voltage parameter for the BGR circuit based on the supply voltage status. When VCC is normal, the BGR uses VCC; when VCC approaches the power down level, the BGR switches to using the boosted voltage VXX. This parameter change ensures the reference voltage remains within the expected range for accurate detection.
Data Source
AI summary
A power down detection circuit that may detect a supply voltage decrease more accurately is provided. The power down detection circuit includes a BGR circuit generating a reference voltage VREF, a resistance division circuit generating a first internal voltage VCC_DIV1 and a second internal voltage VCC_DIV2 based on a supply voltage VCC, a first comparator outputting a reset signal PDDRST when detecting VCC_DIV1<VREF, a second comparator outputting a switching signal SEL when detecting VCC_DIV2<VREF, a charging pump circuit generating a boosted voltage VXX based on the supply voltage VCC, and a switching circuit switching an operating voltage supplied to the BGR circuit to the supply voltage VCC or the boosted voltage VXX based on the switching signal SEL.