Protection Voltage Circuit for Multi-Rail I/O Power Failures
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Solution Overview
Problem
High-speed I/O interface systems face challenges in designing circuits that can tolerate varying power supply voltages, particularly when high-voltage transistors are not suitable for high-speed operations, and power sequencing may not be possible, leading to potential damage from excessive voltage stress.
Innovation Solution
A circuit protection design that generates a protection voltage when VDD is off and VDDQ is on, switching to VDD supply when VDD is on, without additional control logic, ensuring safe voltage levels for core logic circuits during power failures or voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage transistors are used to tolerate higher supply voltages, then voltage tolerance is improved, but operating speed deteriorates
Solution Approach 1:
The transistor system is segmented into two distinct types: high-voltage transistors for I/O interfaces that require voltage tolerance, and low-voltage transistors for core logic that require high-speed operation. This segmentation allows each segment to be optimized for its specific function without compromise
Solution Approach 2:
A protection voltage (VDDPROT) is introduced as an intermediary voltage level that mediates between the high-voltage I/O domain and the low-voltage core logic domain. This intermediary voltage protects low-voltage transistors from excessive voltage stress while allowing high-voltage transistors to operate at higher speeds
2Productivity
If different power supply voltages are used for I/O and core logic, then I/O performance is improved, but circuit complexity increases
Solution Approach 1:
The protection voltage circuit serves multiple functions simultaneously: it acts as a voltage reference for low-voltage transistors, provides over-voltage protection, and enables safe power-up sequencing. This multi-functionality reduces the need for separate protection circuits and control logic
Solution Approach 2:
The protection voltage is generated automatically from the I/O supply voltage through a simple resistor divider network, without requiring external control signals or complex power management logic. The circuit self-regulates to provide appropriate voltage levels
3Reliability
If power sequencing is implemented to protect low-voltage transistors, then transistor protection is improved, but system complexity increases
Solution Approach 1:
The protection voltage is established in advance through a simple resistor divider network before any switching operations occur. This preliminary voltage establishment ensures that low-voltage transistors are protected from the moment the I/O supply is applied, without requiring complex sequencing control
Solution Approach 2:
The protection voltage serves as an intermediary that eliminates the need for complex power sequencing control logic. By providing a naturally derived voltage reference, it simplifies the power management system while maintaining transistor protection
Data Source
AI summary
Apparatus, methods and systems to produce a protection voltage are disclosed. The apparatus includes circuitry to deliver a first supply voltage to a plurality of circuits, where the first supply voltage has a first magnitude, circuitry to deliver a second supply voltage to a part of the plurality of circuits, where the second supply voltage has a second magnitude, and circuitry to deliver a protection voltage to the part of the plurality of circuits when the second supply voltage is LOW and the first supply voltage is HIGH. The protection voltage has a magnitude that is a fraction of the magnitude of the first supply voltage. The apparatus includes circuitry that causes the delivery of the second supply voltage to the part of the plurality of circuits when the second supply voltage is turned HIGH subsequent to the second supply voltage being LOW when the first supply voltage is HIGH.