Split-Domain Input Buffer Circuit for SOA-Safe High-Voltage I/O
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Solution Overview
Problem
Low voltage devices used in high voltage domains face Safe Operating Area (SOA) violations due to the need to transmit and receive data at higher voltages, leading to increased pin leakage when resistive voltage dividers are employed.
Innovation Solution
An input buffer circuit with separate high and low input voltage domains, utilizing a signal splitter and combiner circuit to independently control voltage levels, and a level shifter to downshift high voltage signals, preventing SOA violations without the need for resistive voltage dividers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If low voltage devices are used in high voltage domains to achieve high speed and low area, then speed and area are improved, but Safe Operating Area violations occur due to high voltage exposure
Solution Approach 1:
The input buffer circuit is segmented into two independent voltage domains: a high voltage domain (VIH) for receiving high voltage signals and a low voltage domain (VIL) for processing signals at safe voltage levels. The signal path is divided such that high voltage signals are split into upper and lower portions, with only the lower portion directly connected to low voltage devices, preventing SOA violations while maintaining high speed operation.
2Reliability
If a resistive voltage divider is used to step down pad voltage to protect low voltage devices, then voltage protection is achieved, but pin leakage increases
Solution Approach 1:
The harmful resistive voltage divider is extracted and removed from the circuit. Instead, the patent directly connects the lower portion of the split high voltage signal to the low voltage domain through carefully designed buffer circuits, achieving voltage protection without the leakage penalties of resistive dividers.
Solution Approach 2:
Buffer circuits act as intermediaries between the high voltage domain and low voltage domain. These buffers translate and isolate voltage levels without requiring resistive dividers, preventing direct high voltage exposure to low voltage devices while minimizing leakage current.
3Adaptability or versatility
If high voltage is used for I/O buffers to transmit and receive data, then voltage compatibility is improved, but low voltage devices suffer SOA violations
Solution Approach 1:
The patent introduces a voltage domain dimension by creating separate high voltage (VIH) and low voltage (VIL) domains. High voltage compatibility is achieved in the VIH domain for signal reception, while the VIL domain maintains safe operating conditions for low voltage devices through controlled signal routing and level shifting.
Data Source
AI summary
An input circuit receives an input voltage and generates a digital output. A first signal splitter generates a lower signal which tracks the input voltage in a range of a first voltage level and a second voltage level and provides a first control signal based on the upper signal. A second signal splitter generates an upper signal which tracks the input voltage in a range of the second voltage level and a third voltage level and provides at least one control signal based on the upper signal. The third voltage level is greater than the second voltage level which is greater than the first voltage level. A level shifter receives the at least one control signal from the second signal splitter and provides a third control signal, and a combiner circuit generates the digital output as a logical combination of the first and third controls signals.