ADC Protection Circuit Using Switched Resistor Sampling
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Solution Overview
Problem
In FTTH systems, analog-to-digital converters are damaged due to excessive photocurrents exceeding their sampling voltage range, causing analog voltages to exceed the converter's capacity.
Innovation Solution
An analog-to-digital converter protection circuit is implemented, featuring an analog switch, an analog-to-digital converter, and a controller with a series circuit of resistors, where the controller adjusts the sampling end to ensure the analog voltage remains within the sampling voltage range by triggering the analog switch to change the conduction sampling end based on digital voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sampling resistor converts photocurrent to analog voltage, then the analog-to-digital converter can perform conversion, but the analog voltage may exceed the sampling voltage range causing damage
Solution Approach 1:
The protection circuit segments the sampling process by dividing the single sampling resistor into multiple parallel resistors (R1, R2, R3, R4), each providing a different voltage division ratio. This segmentation allows the system to handle different photocurrent ranges by selecting appropriate resistors, preventing any single resistor from generating excessive voltage that could damage the ADC.
Solution Approach 2:
The protection circuit achieves multi-functionality by combining multiple parallel resistors with an analog switch to create a universal sampling mechanism. The same circuit structure can adapt to different optical power levels by switching between resistors, making the circuit universally applicable across varying signal conditions without requiring separate protection circuits for different ranges.
2Adaptability or versatility
If the analog switch switches sampling ends dynamically, then the sampling voltage range is maintained, but the control complexity increases
Solution Approach 1:
The control mechanism performs preliminary action by pre-configuring multiple sampling ends (first sampling end, second sampling end, etc.) with different voltage division characteristics. The controller evaluates the optical signal characteristics in advance and selects the appropriate sampling end before the actual ADC conversion, preventing voltage range violations rather than reacting to them.
Solution Approach 2:
The protection circuit implements feedback by having the controller continuously monitor the digital voltage output from the ADC and adjust the analog switch state accordingly. When the digital voltage indicates that the analog voltage is approaching or exceeding the sampling voltage range, the controller feeds back a control signal to switch to a different sampling end with appropriate voltage division, maintaining the voltage within acceptable ranges.
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
This solution prevents damage to the analog-to-digital converter by ensuring it samples analog voltages within its voltage range, maintaining sampling precision and avoiding converter damage from excessive voltages.
Implementation Method 1
The series circuit is configured to convert a photocurrent outputted by the BOSA into an analog voltage
Implementation Method 2
the analog switch is configured to output, to the analog-to-digital converter, an analog voltage sampled by a conduction sampling end of the analog switch
Data Source
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AI summary
An analog-to-digital converter protection circuit, a method for controlling an analog-to-digital converter protection circuit, and a controller are disclosed. The analog-to-digital converter protection circuit includes: an analog switch, an analog-to-digital converter, a controller, and a series circuit including at least two resistors connected in series. The series circuit is configured to convert a photocurrent into an analog voltage. The analog switch is configured to output, to the analog-to-digital converter, an analog voltage sampled by a conduction sampling end. A first sampling end serves as the conduction sampling end to conduct to an output end of the analog switch. The analog-to-digital converter is configured to generate a digital voltage. The controller is configured to: when the digital voltage is greater than or equal to a preset voltage threshold, output a control signal to the analog switch, to trigger the analog switch to control a second sampling end to serve as the conduction sampling end to conduct to the output end of the analog switch, where an analog voltage sampled by the second sampling end is less than an analog voltage sampled by the first sampling end; and when the digital voltage is less than the preset voltage threshold, output the digital voltage. The analog-to-digital converter can sample an analog voltage within a sampling voltage range of the analog-to-digital converter by using the foregoing circuit.