Input Circuit Switching to Prevent Power-Line Current Backflow
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Solution Overview
Problem
Current integrated circuits face issues with current backflow during power off, leading to voltage retention and errors when turned on again due to signal reflection and termination resistor configurations, which affect the resetting of sink integrated circuits.
Innovation Solution
The integration of a control circuit with pull-up and bulk controlled switches, along with an ESD bus and bus connecting circuit, manages the electrical connection between bonding pads and power lines to prevent current backflow by controlling the switches based on voltage levels, ensuring the power line is maintained at ground voltage during power off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a termination resistor is connected between bonding pad and power line to reduce signal reflection and increase transmission speed, then communication speed and signal quality are improved, but current backflow occurs to power line when electronic product is turned off, causing voltage retention and errors
Solution Approach 1:
The control circuit detects power voltage levels in advance and proactively switches the pull-up switch and bulk controlled switch to appropriate states before current backflow can occur. When power voltage drops to ground level, the control circuit preemptively turns off the pull-up switch and connects the bulk node to ground, preventing the bonding pad from feeding current back to the power line through the termination resistor.
Solution Approach 2:
The bulk controlled switch acts as an intermediary element between the bonding pad and power line. By controlling the connection state of the bulk node, it mediates the electrical relationship between these components, enabling the circuit to prevent current backflow while maintaining normal signal transmission functionality through the termination resistor.
2Reliability
If pull-up switch and bulk controlled switch are added to prevent current backflow, then power line voltage accuracy is improved, but device complexity increases
Solution Approach 1:
The control circuit serves multiple functions: it monitors power voltage levels, controls the pull-up switch state, and manages the bulk controlled switch state. By integrating these functions into a single control unit, the design achieves current backflow prevention without proportionally increasing overall circuit complexity.
Solution Approach 2:
The control circuit combines voltage detection, switch control, and bulk node management into a unified control mechanism. This merging of functions allows the circuit to achieve reliable current backflow prevention while minimizing the increase in device complexity through integrated design.
Data Source
AI summary
An integrated circuit capable of preventing current backflow to a power line is provided. The integrated circuit includes an input circuit. The input circuit includes a bonding pad and a pull-up circuit, a pull-up switch, a bulk controlled switch and a control circuit. The pull-up switch includes a first control node and a first bulk node. The bulk controlled switch includes a second control node and a second bulk node. The control circuit controls the first and second control nodes according to an internal signal, a power voltage of the power line and a pad voltage of the bonding pad. When the power voltage is a predetermined voltage, the control circuit turns on the bulk controlled switch. When the power line is at a ground voltage and the bonding pad voltage is at the predetermined voltage, the control circuit turns off the bulk controlled switch and the pull-up switch.