Adaptive Body Bias Switch Cell for Shared Test Pad Access
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Solution Overview
Problem
Existing technologies face challenges in connecting multiple body bias generators to a test signal pad without external additional supply voltages, and in implementing a well voltage bias switch cell that can switch between high and low resistive states without requiring high and low supply voltages.
Innovation Solution
An adaptive body biasing system that includes at least one biased logic domain, an adaptive body bias generator for generating variable bias voltages, a test pad for accessing these voltages, and a bias switch cell that connects the generator to the test pad. The bias switch cell has a high-resistive off state during normal operation and can switch to a low-resistive on state during test operations, allowing for electrical isolation and safe access to body bias nets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple body bias generators are connected to a test pad, then test accessibility is improved, but device complexity increases
Solution Approach 1:
The patent divides the system into multiple body bias generator circuits, each independently generating bias voltages for different logic domains. Each generator is segmented with its own switch cell and level shifter, allowing individual testing through a single shared test pad without requiring multiple external pads.
Solution Approach 2:
The test pad serves multiple functions: it is used for normal operation as a regular I/O pad and for test operations where it provides access to body bias voltages from multiple generators. The bias switch cells provide universal switching capability that can connect any generator to the test pad as needed.
2Adaptability or versatility
If bias switch cell uses high and low supply voltages for switching, then switching capability is improved, but device complexity increases
Solution Approach 1:
The bias switch cell uses the body bias voltages themselves (VNB and VNP) to control the switching operation. The switch cell generates its own control signals by processing the bias voltages through level shifters, eliminating the need for external high and low supply voltages. The system serves itself by using its operating voltages for control purposes.
Solution Approach 2:
The patent changes the control parameter from external supply voltages to the body bias voltages themselves. By using the bias voltages as control signals and processing them through level shifters, the system achieves switching capability without requiring additional high and low supply voltage rails.
3Ease of operation
If test pad is connected to body bias generator during normal operation, then test accessibility is improved, but reliability decreases
Solution Approach 1:
The connection between the test pad and body bias generator is made dynamic through the bias switch cell. During normal operation, the switch cell isolates the test pad from the bias generator. During test operations, the switch cell dynamically connects them. This dynamic switching allows the system to adapt its connectivity based on operational mode.
Solution Approach 2:
The test pad connection is extracted from the normal operational path. The bias switch cell separates the test function from the normal biasing function, allowing the test pad to be connected only when needed for testing while maintaining isolation during normal operation to preserve reliability.
Data Source
AI summary
An adaptive body biasing system for silicon on insulator semiconductor devices includesat least one biased logic domain;at least one adaptive body bias generator for generating variable bias voltage; at least one test pad for accessing the generated bias voltage generated by the at least one adaptive body bias generator; and at least one bias switch cell connecting the at least one adaptive body bias generator to the at least one test pad. The at least one bias switch cell is in high-resistive off state during normal operation of the semiconductor device and can be switched to low-resistive on state during test operation. The at least one adaptive body bias generator is connected to the at least one biased logic domain.