Multiplexed ADC Input Protection Against Injection Current Errors
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Solution Overview
Problem
Analog-to-digital converters (ADCs) with multiplexing structures are vulnerable to adverse effects from injection currents when a voltage higher than the internal voltage is applied to disabled input ports, leading to signal interference and output errors.
Innovation Solution
The ADC incorporates a transmission circuit that selectively transmits input signals and a discharge circuit with a pull-down transistor to divert overcurrents to ground, preventing injection current interference by using control signals to manage the flow of signals and currents between nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multiplexing structure is used in ADC to handle multiple analog signals, then the ADC can process multiple input channels, but disabled input ports become vulnerable to injection current interference from malfunctioning sensors
Solution Approach 1:
A discharge circuit is introduced as an intermediary component between the disabled input port and the ADC core. This discharge circuit, controlled by the control signal generation unit, provides a safe path for injection currents to flow to ground without affecting the ADC operation, thus protecting the system while maintaining multi-channel capability
Solution Approach 2:
The harmful injection current is extracted and diverted from the main signal path by the discharge circuit. By separating the current path of malfunctioning sensors from the ADC input, the harmful effect is removed while the useful multi-channel functionality is preserved
2Adaptability or versatility
If disabled input ports are left connected to handle future channel switching, then channel switching is enabled, but overcurrent from malfunctioning sensors flows into the ADC during off state
Solution Approach 1:
The discharge circuit is dynamically controlled based on the operational state of each input channel. The control signal generation unit activates the discharge circuit only for disabled input ports, allowing the system to adapt its protection mechanism dynamically without affecting enabled channels, thus maintaining both reliability and channel switching capability
3Productivity
If transmission gates are used to select input channels, then efficient signal transmission is achieved, but the transmission path becomes vulnerable to injection current when gates are closed
Solution Approach 1:
The discharge circuit acts as a mediator that provides an alternative current path parallel to the transmission gate. When the transmission gate is closed for a disabled channel, the discharge circuit intercepts injection currents before they can affect the ADC, thus protecting the transmission path while maintaining its efficiency for enabled channels
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 effectively limits the impact of injection currents on the ADC's output, maintaining accuracy within the least significant four bits of the digital signal and ensuring reliable analog-to-digital conversion.
Implementation Method 1
a discharge circuit selectively discharging the input signal of the first node in response to another control signal
Data Source
AI summary
An electronic circuit includes a transmission circuit transmitting an input signal of a first node as an output signal of a second node in response to a control signal and a discharge circuit selectively discharging the input signal of the first node in response to the control signal.