RFID Power-On Reset Circuit Using RF Signal Sensing
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Solution Overview
Problem
Conventional power-on reset circuits in RFID devices with nonvolatile ferroelectric memory fail to generate a stable power-on reset signal when the power voltage drops below a threshold, especially during short power-off periods, leading to incomplete power-on reset operations.
Innovation Solution
An RFID device with a nonvolatile ferroelectric memory that includes a power-on reset unit, a radio frequency signal sensing unit, and a power-on reset mixer to generate a power-on reset signal based on the voltage levels of the power sensing signal and the radio frequency sensing signal, allowing the device to stabilize the power source and sense the off period of the radio frequency signal independently of the power voltage level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power-on reset circuits are used that generate reset signals based on power voltage, then the circuit structure is simple, but the power-on reset signal cannot be generated reliably when power voltage drops below threshold during short power-off periods
Solution Approach 1:
The power-on reset circuit is segmented into multiple independent sensing units: a power voltage sensing unit that monitors power voltage levels and a radio frequency signal sensing unit that detects RF signal presence. Each unit independently evaluates its respective condition and generates separate sensing signals, which are then combined to determine the final power-on reset signal. This segmentation allows reliable reset signal generation even when power voltage fluctuates, as the RF signal sensing provides an additional independent criterion.
Solution Approach 2:
The circuit performs preliminary sensing of both power voltage levels and RF signal presence before generating the power-on reset signal. The power voltage sensing unit and RF signal sensing unit continuously monitor their respective parameters in advance, preparing sensing signals that reflect the current system state. This preliminary action ensures that when power is applied or restored, the reset signal is generated based on pre-evaluated conditions, preventing failures during short power-off periods.
2Reliability
If the power source is not stabilized, then the circuit operation is simple and responsive, but the power voltage level may drop during short off periods causing incomplete reset operations
Solution Approach 1:
A capacitor is introduced as an intermediary energy storage element connected to the power voltage receiving terminal. This capacitor stabilizes the power source by maintaining voltage levels during short off periods, preventing voltage drops that would cause incomplete reset operations. The capacitor acts as a buffer, releasing stored energy when power is temporarily interrupted, ensuring continuous operation of the sensing circuits and complete execution of reset operations.
Solution Approach 2:
The capacitor provides beforehand cushioning by storing energy in advance during normal operation. When power voltage drops or is temporarily interrupted, this pre-stored energy cushions against voltage fluctuations, maintaining stable operation of the power-on reset circuit. This prior cushioning ensures that the sensing units continue to function properly and generate accurate sensing signals even during short power disturbances.
Data Source
AI summary
A RFID device having a nonvolatile ferroelectric memory includes an analog block. A power-on reset unit configured to sense a power voltage and output a power sensing signal is included in the analog block. A radio frequency signal sensing unit is configured to sense the level of a detecting signal corresponding to a radio frequency signal received by the antenna of the RFID device and outputs a radio frequency sensing signal. A power-on reset mixer is configured to synthesize the power sensing signal and the radio frequency sensing signal and outputs a power-on reset signal according to the voltage levels of the power sensing signal and the radio frequency sensing signal.