Ground Switch With Charge Pump And Clamping Circuit For RFID Parasitic Capacitance
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Solution Overview
Problem
RFID tags face performance issues due to parasitic capacitance caused by ground switches, leading to non-linear behavior and power-dependent de-tuning, which affects their reliability and efficiency, especially under varying field conditions and electrostatic discharge events.
Innovation Solution
A ground switch with a charge pump and clamping circuit that adjusts the AC input signal with a DC offset voltage, allowing the ground switch to operate stably and reduce parasitic capacitance, ensuring a stable ground for RFID devices by controlling the amplitude of the input signal and threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If devices MNavss, MNbvss are used to withstand all operating conditions and ESD events, then reliability is improved, but threshold voltage increases and parasitic capacitance worsens
Solution Approach 1:
The ground switch is divided into two separate switches (first ground switch and second ground switch) with different threshold voltages. These switches operate at different voltage levels, segmenting the ground switching function to reduce overall parasitic capacitance while maintaining reliability under various operating conditions and ESD events.
Solution Approach 2:
Different regions of the circuit use ground switches with different threshold voltages tailored to their specific requirements. The first ground switch handles higher voltage conditions while the second handles lower voltage conditions, optimizing local performance and reducing parasitic effects in each region.
2Reliability
If ground switch is used to ensure no high negative voltage at input, then safety is improved, but parasitic capacitance leads to non-linear behavior and performance degradation
Solution Approach 1:
The ground switching function is segmented into two switches with different threshold voltages. This segmentation reduces the total parasitic capacitance compared to a single switch, thereby improving the linearity of the input capacitor behavior while still preventing high negative voltage at the input.
3Device complexity
If single ground switch is used, then device complexity is reduced, but parasitic capacitance causes power dependent de-tuning
Solution Approach 1:
Although adding a second ground switch increases device complexity, it segments the parasitic capacitance into smaller portions. This segmentation reduces power-dependent de-tuning and improves frequency stability, particularly in high-power applications where a single switch would cause significant performance degradation.
Data Source
AI summary
A ground switch is disclosed. The ground switch includes an antenna port, a pair of switching devices coupled with the antenna port and a charge pump coupled with the pair of devices and configured to turn on/off the pair of devices based on an AC input signal received through the antenna port and a DC offset voltage added to the AC input signal. The ground switch further includes a clamping circuit to clamp an output of the charge pump. The ground switch is configured to provide a stable ground to components of devices such that a radio frequency identification (RFID) device.