Integrated Voltage Switching Circuit With Input Clamping for Test Mode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Integrated circuits often require switching to a specific operating mode, such as a test mode, but lack a dedicated mode selection pin, making it difficult to do so effectively.
Innovation Solution
An integrated circuit design that includes a multiplexer with a gate circuit and clamping means, allowing switching to a particular operating mode by applying a high voltage to a signal input, with voltage detection and clamping to prevent damage to sensitive components, even without a dedicated mode selection pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a high voltage is applied to the signal input to switch the circuit to test mode, then the mode switching capability is improved, but the risk of damaging voltage-sensitive components increases
Solution Approach 1:
A clamping circuit is introduced as an intermediary between the signal input and the multiplexer input. This clamping circuit comprises a clamping element (such as a diode or transistor) connected between the multiplexer input and the supply terminal, which mediates the voltage transmission by limiting the maximum voltage level that reaches the voltage-sensitive multiplexer, thus enabling high voltage mode switching without damaging the internal components
Solution Approach 2:
The circuit utilizes voltage level detection to trigger mode switching. When the input voltage exceeds a threshold level (indicating test mode activation), the voltage detection means detects this parameter change and activates the gate circuit to control the multiplexer, thereby switching from normal operation mode to test mode based on the voltage parameter change
2Reliability
If a dedicated mode selection pin is used for switching to test mode, then the reliability of mode switching is improved, but the device complexity increases
Solution Approach 1:
The signal input terminal is designed to serve dual purposes: it functions as a normal data input during regular operation and as a mode selection input when a high voltage level is applied. This multi-functionality eliminates the need for a separate dedicated mode selection pin, reducing device complexity while maintaining reliable mode switching capability through the voltage-level-dependent multiplexer control
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
Enables switching to a test mode or similar without a dedicated mode selection pin, ensuring the circuit operates safely and reliably by using a multiplexer and clamping circuitry to manage high input voltages, allowing operation up to 8V without damaging voltage-sensitive components.
Implementation Method 1
Clamping means are provided that limit the voltage at the first input of the multiplexer
Implementation Method 2
a diode-connected MOS transistor connected between the first input of the multiplexer and the first supply terminal
Data Source
AI summary
An integrated circuit can be switched between operating modes without the need for a dedicated mode selection pin. A circuit for operation at a specified maximum supply voltage comprises first and second supply terminals, a first signal input for application of a regular input signal, a second signal input, and an output. The circuit further comprises a multiplexer with first and second inputs connected to the first and second signal inputs, respectively, for selectively switching either of the first and second signal inputs to the output under control of a selection signal. A gate circuit provides the selection signal to the multiplexer. The input of the gate circuit is driven by control circuitry. Clamping circuitry is provided that limits the voltage at the first input of the multiplexer. With such a circuit design, a relatively high voltage applied to the first signal input will switch the circuit to another operating mode, such as a test mode.