Light Compensation Current Mirror for Unpackaged RFID IC Biasing
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Solution Overview
Problem
Unpackaged integrated circuits in RFID tags experience operational disturbances due to light-induced current, which affects the bias voltage and current required for proper circuit operation.
Innovation Solution
A compensation circuit with a current mirror and a second light sensitive circuit component is implemented to match and compensate for the light-induced current in the first light sensitive circuit component, ensuring that the output current does not include a light-induced component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the integrated circuit is left unpackaged to reduce manufacturing cost and complexity, then ease of manufacture is improved, but the circuit becomes sensitive to light-induced current which disturbs operation
Solution Approach 1:
The patent introduces a compensation circuit that uses a second light-sensitive component (N-well resistor 213) to generate a compensating current that exactly cancels the harmful light-induced current from the first light-sensitive component (N-well resistor 206). By using the same light-sensitive effect in the compensation circuit, the harmful photocurrent is converted into a useful compensating signal that restores the bias current to its correct value.
Solution Approach 2:
The compensation circuit acts as an intermediary between the light source and the main bias circuit. It introduces additional components (second N-well resistor, current mirror transistors 202-212) that mediate the light effect by generating a counter-current through the same photocurrent mechanism, thereby eliminating the net harmful effect on the bias current.
2Reliability
If packaging is added to protect the chip from light, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
Instead of using physical packaging to block light, the patent converts the harmful light effect into a beneficial compensating signal. The compensation circuit uses the same light-sensitive N-well resistor material to generate a photocurrent that cancels the harmful current, eliminating the need for light-blocking packaging while maintaining operational stability.
3Use of energy by moving object
If the bias circuit uses light-sensitive N-well resistors to generate bias current, then power consumption is reduced, but light exposure creates parallel photocurrent that disturbs operation
Solution Approach 1:
The patent transforms the harmful parallel photocurrent into a useful compensating current. The second N-well resistor 213 generates a photocurrent that is mirrored through transistors 211 and 212 to subtract from the harmful photocurrent of the first N-well resistor 206, thereby converting the harmful effect into a benefit that restores the bias current accuracy.
Solution Approach 2:
The compensation circuit implements a feedback mechanism where the light-induced current in the second N-well resistor 213 is sensed and used to generate a compensating signal through the current mirror. This feedback loop continuously counteracts the light-induced current in the first N-well resistor 206, maintaining accurate bias current delivery even under light exposure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compensation circuit effectively removes the light-induced current component, maintaining accurate bias current delivery to the integrated circuit and reducing power consumption, even when exposed to light.
Implementation Method 1
In the semiconductor material of the unpackaged chip, light photons can create electron-hole pairs, which generate charge carriers. The photo-generated charge carriers may diffuse through the backside of the semiconductor substrate and part of them may reach pn junctions resulting in a reverse current flow (or photocurrent)
Data Source
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AI summary
A circuit for compensating for the effects of light exposure is provided. The circuit includes a first circuit and a light compensation circuit. The first circuit has an output terminal for providing a first current, wherein at least a portion of the first current is a function of a first light sensitive circuit component. The compensation circuit has a current mirror and a second light sensitive circuit component. The current mirror has an input terminal coupled to receive a second current that is mirrored from the first current, and an output terminal coupled to provide a third current responsive to the second current. The second light sensitive circuit component is configured to be similar to the first light sensitive circuit component and to compensate for a light induced current provided by the first light sensitive circuit component so that the third current is provided without a light induced current component.