Selectable GPIO Input Buffers for Low-Voltage Static Current Blocking
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Solution Overview
Problem
Conventional CMOS input buffers in microcontrollers experience static current draw when interfacing with external devices operating at a lower voltage domain than the microcontroller's supply voltage domain.
Innovation Solution
The implementation of a general purpose input in a microcontroller that includes two input buffers, one supplied by the microcontroller's supply voltage and another by a regulated supply voltage at a lower voltage domain, with control logic to selectively enable or disable these buffers via control signals, thereby managing static current draw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single input buffer supplied by the microcontroller's supply voltage is used, then the input buffer can operate at the full voltage domain, but static current draw occurs when interfacing with external devices at a lower voltage domain
Solution Approach 1:
The input buffer is segmented into two separate buffers: a first input buffer supplied by the microcontroller's supply voltage (VDD) and a second input buffer supplied by a regulated supply voltage (VREG) at a lower voltage domain. This segmentation allows each buffer to operate independently at its appropriate voltage level, preventing static current draw when interfacing with external devices at lower voltage domains while maintaining full voltage domain operation capability when needed.
2Loss of energy
If dual input buffers are implemented to manage voltage domains, then static current draw can be controlled, but device complexity increases
Solution Approach 1:
The system dynamically selects which input buffer to use based on the operating conditions. Control logic monitors the voltage domain requirements and selectively enables either the first input buffer (for full voltage domain operation) or the second input buffer (for lower voltage domain interfacing), optimizing both energy efficiency and device functionality without requiring both buffers to be permanently active.
Data Source
AI summary
One or more embodiments relate, generally, to microcontroller input/output (I/O) and limiting or disabling static current draw at general purpose inputs, including during low power situations where a voltage input may be lower than a supply voltage. In some embodiments, a general purpose input may include selectable input buffers and logic that is configured to selectively enable an input buffer associated with a voltage domain substantially the same as an input voltage of the general purpose input, and selectively disable the other input buffers.