Post Driver Voltage Clamping for Core Device Protection
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Solution Overview
Problem
High density integrated circuits, such as SOC and 3D ICs, face challenges in providing adequate I/O drivers that can handle the higher voltages required for interfacing with components like printed circuit board traces without overstressing core devices operating at lower voltages.
Innovation Solution
A post driver design using core device MOSFETs with a voltage clamping element, such as a diode, to manage the voltage difference between the core and I/O voltage ranges, preventing overstress on the core devices by ensuring the voltage drop across them remains within the permissible operating range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If core devices are used to provide I/O drivers, then device density and integration are improved, but the devices become susceptible to overstress and damage from higher I/O voltages
Solution Approach 1:
A voltage clamping element (diode) is introduced as an intermediary component between the core device and the I/O interface. This diode clamps the voltage across the core device to remain below the maximum operating voltage even when higher I/O voltages are applied, thereby protecting the core device from overstress while enabling high-density integration
Solution Approach 2:
The voltage clamping element is positioned in advance to prevent voltage spikes from damaging the core device. By placing the protective element before the harmful voltage can reach the core device, the system proactively prevents overstress conditions rather than reacting after damage occurs
2Power
If higher voltages are applied to I/O interfaces, then driving capability for external components is improved, but core devices operating at lower voltages are overstressed
Solution Approach 1:
The voltage clamping element acts as a mediator that allows high voltage to be applied at the I/O interface while preventing this high voltage from being transmitted to the core device. The diode conducts only when the voltage exceeds the clamping threshold, thereby absorbing excess voltage and protecting the core device from stress
3Reliability
If separate I/O devices are used instead of core devices, then voltage compatibility is improved, but area and cost increase
Solution Approach 1:
The voltage clamping element enables core devices to serve dual functions: both as computational logic elements and as protected I/O drivers. By adding the simple protective diode, the same core device can handle both high-speed digital logic and high-voltage I/O interfacing, eliminating the need for separate dedicated I/O devices and reducing overall chip area
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 post driver effectively handles I/O voltages outside the core device operating range without overstressing the MOS core devices, ensuring reliable operation and reducing the risk of damage, while also offering space and cost savings in implementation.
Implementation Method 1
having a voltage clamping element connecting the first intermediate node to the second intermediate node and having a threshold voltage greater than the difference between the I/O voltage range and the core voltage range
Data Source
AI summary
A post driver implemented using core device transistors to drive an output connection between the high and low voltage levels of an I/O voltage range. The post driver is made from a plurality of core devices operable within a core voltage range that is less than the I/O voltage range. The plurality of core devices is cascaded between upper and lower power connections set to the full I/O voltage range. The post driver has a voltage clamping element, such as a diode, having a predefined threshold voltage and connected to the core devices so as to maintain the voltage difference across the terminals thereof within the core voltage range.