Multi-Voltage Power-On Reset Circuit for Random Supply Sequences
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Solution Overview
Problem
Conventional power-on reset (POR) techniques for multi-voltage circuits are sequence-dependent, leading to malfunctions and excessive current consumption, as they only monitor the ramp-up of the last power supply voltage, making them susceptible to random power-up sequences and resulting in system failures.
Innovation Solution
A sequence-independent POR methodology and circuit that asserts the chip reset upon the ramp-up of the first power supply signal and de-asserts it upon the ramp-up of the last power supply signal, regardless of the power supply ramp-up sequence, using a POR circuit with pull-up and pull-down circuits to generate a reset signal that remains asserted while at least one but not all power supply signals have ramped up, and includes a control circuit to minimize current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional POR techniques monitor only the last power supply voltage ramp-up, then the POR signal generation is simplified, but the circuit reliability deteriorates due to sequence-dependent operation and susceptibility to random power-up sequences
Solution Approach 1:
The POR circuit is segmented into multiple independent voltage domain detectors, each monitoring a specific power supply voltage domain. This segmentation allows the circuit to track the ramp-up status of each voltage domain independently, enabling sequence-independent operation while maintaining simplified individual detector designs
Solution Approach 2:
The POR circuit is designed with multi-functionality to handle multiple voltage domains universally. The circuit can detect and respond to power-up sequences regardless of which voltage domain ramps up first, making it adaptable to different power supply configurations and eliminating the need for sequence-specific design modifications
2Use of energy by moving object
If conventional POR techniques use sequence-dependent monitoring, then the current consumption is reduced, but the circuit malfunctions occur due to undetermined POR signal state during partial voltage ramp-up
Solution Approach 1:
The POR circuit employs feedback mechanisms where the detected voltage domain ramp-up status is continuously monitored and fed back to control the POR signal generation. This feedback ensures that the POR signal remains asserted (active) during the transition period when not all voltage domains have completed ramp-up, preventing circuit malfunctions while managing current consumption through controlled signal assertion
Solution Approach 2:
The POR circuit performs preliminary detection of voltage domain ramp-up status before full power-up is complete. By detecting the first ramping voltage domain and asserting the POR signal in advance, the circuit prepares the system for proper initialization, preventing contention in tri-state logic and memory malfunction before they can occur
3Device complexity
If the POR signal is asserted only after all power supply voltages ramp-up, then the circuit operation is simplified, but excessive current consumption occurs due to contention in tri-state logic and memory malfunction
Solution Approach 1:
The POR circuit performs preliminary detection of voltage domain ramp-up status before full power-up is complete. By detecting the first ramping voltage domain and asserting the POR signal in advance, the circuit prepares the system for proper initialization, preventing contention in tri-state logic and memory malfunction before they can occur
Solution Approach 2:
The POR signal acts as an intermediary control signal that mediates between the voltage domain detectors and the circuit modules. It coordinates the power-up sequence by keeping circuit modules in a reset state during voltage transitions, preventing direct conflicts and excessive current consumption while maintaining simplified operation control
Data Source
AI summary
A power-on reset (“POR”) methodology and circuit for an electronic circuit using multiple supply voltage domains asserts a reset signal upon ramp up of the first supply voltage signal, maintains the reset signal until all of the supply voltage signals have ramped up, and de-asserts the reset signal after all of the supply voltage signals have ramped up. Practical embodiments of the POR circuit include a control circuit that reduces static and/or dynamic current leakage associated with the operation of the POR circuit.