MPO Output Circuitry Filtering for EMI and Power Injection Immunity
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Solution Overview
Problem
Multi-purpose output (MPO) circuitry in semiconductor processing devices is susceptible to electrical stress and electromagnetic interference, which can cause unintended operation and affect other circuits, necessitating improved electromagnetic compatibility.
Innovation Solution
The implementation of high and medium cutoff frequency filters, along with a strong pull-down device, to redirect and filter out specific frequency signals, ensuring the MPO circuit remains off during direct power injection and reduces emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MPO circuitry is used to communicate signals for various purposes, then the circuitry provides multi-functional output capability, but the circuitry becomes susceptible to electrical stress and electromagnetic interference
Solution Approach 1:
A current sink circuit is introduced as an intermediary between the MPO circuitry and external components. This current sink acts as a mediator that absorbs electrical stress and electromagnetic interference, protecting the MPO circuitry while allowing it to maintain its multi-functional output capability. The current sink includes a transistor configured to sink current during direct power injection events, preventing these events from affecting the MPO circuit operation.
2Adaptability or versatility
If MPO circuitry is coupled to external components, then the circuitry can interface with external devices, but the circuitry generates emissions that affect other circuits
Solution Approach 1:
The current sink circuit converts harmful electromagnetic emissions into a beneficial protective mechanism. During direct power injection events, the current sink actively sinks the injected current, preventing it from propagating through the MPO circuitry and generating harmful emissions. The transistor is specifically configured to enter saturation mode during such events, effectively absorbing the electrical stress and converting what would be harmful emissions into a controlled current path.
3Reliability
If the output transistor is switched ON during direct power injection, then the circuitry can handle power injection events, but the transistor may be damaged or cause unintended operation
Solution Approach 1:
The current sink circuit applies preliminary anti-action by being pre-configured to counteract direct power injection events before they can affect the output transistor. The current sink transistor is biased and configured to automatically activate during power injection events, creating an opposing current path that prevents the injection current from turning on the output transistor or causing unintended operation. This protective action is built into the circuit configuration rather than being a reactive measure.
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 solution enhances the MPO circuit's immunity to electrical stress and reduces emissions, preventing unintended operation and minimizing interference with other circuits.
Implementation Method 1
A first low pass filter with a high cutoff frequency is added near current sources to prevent an output transistor from being switched ON during direct power injection
Implementation Method 2
a stronger pull-down device is implemented in the driver to maintain input and output at a low level to insure the voltage at the control gate of the output transistor is low enough to avoid turning the transistor ON in an OFF state
Data Source
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AI summary
An integrated circuit can comprise an output terminal, a power transistor having a first current electrode coupled to the output terminal and a second current electrode coupled to a power supply terminal, a driver having an output coupled to a control electrode of the power switch, a capacitor having a first terminal coupled to the output terminal and a second terminal coupled to a circuit node, a first low pass filter coupled between the circuit node and an input of the driver, the first low pass filter having a first cut off frequency, a set of current sources, and a second low pass filter coupled between the circuit node and an output of the set of current sources. The second low pass filter can have a second cut off frequency that is higher than the first cut off frequency.