Power-on Clear Circuit Current Limiting for Semiconductor Devices
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Solution Overview
Problem
Conventional power-on clear circuits in semiconductor integrated circuits experience increased current consumption due to through currents when the low power supply voltage has not yet risen, leading to indefinite output signals and potential short-circuits.
Innovation Solution
A power-on clear circuit is designed with a bias current generation circuit, a first transistor, an inverter unit, and a signal outputting unit, where the bias current generation circuit generates a bias current and transmits it to a first node, and the inverter unit operates based on the power supply voltage to output a power-on clear signal, reducing current consumption by limiting the current flowing through the inverter stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional power-on clear circuit using cascaded inverters is used, then the circuit can generate power-on clear signals, but current consumption increases due to through currents when the low power supply voltage is at intermediate potential
Solution Approach 1:
The patent introduces a current limiting circuit as an intermediary component between the inverter stages. This current limiting circuit acts as a mediator that restricts the through current flowing between power supply lines when the low power supply voltage is at intermediate potential, thereby preventing excessive current consumption while maintaining the power-on clear signal generation function
Solution Approach 2:
The patent changes the electrical parameter characteristics by introducing resistance elements in the current limiting circuit. These resistance elements modify the current flow characteristics during the transition period, limiting the current to acceptable levels while still allowing the inverter stages to function properly for generating the power-on clear signal
2Stability of the object's composition
If the low power supply voltage rises slowly after power-on, then the regulator can generate stable voltage, but the output signal becomes indefinite and through currents may occur
Solution Approach 1:
The patent applies preliminary anti-action by pre-establishing current limiting protection circuits before the through current problem occurs. The current limiting circuits are designed to automatically activate during the voltage transition period, preventing the harmful through current from occurring in the first place rather than correcting it after it occurs
Solution Approach 2:
The patent implements beforehand cushioning by introducing resistance elements that cushion the current flow during the critical transition period. These resistance elements absorb and limit the through current that would otherwise occur when the low power supply voltage is at intermediate potential, protecting the circuit from harmful current spikes
Data Source
AI summary
A power-on clear circuit includes a bias current generation circuit having one end connected to a first line supplied with a first power supply voltage, the other end connected to a second line kept at a fixed potential, and configured to generate a bias current, and to transmit the bias current to a first node; a first transistor having a first terminal connected to the second line, a second terminal connected to the first node, and a control terminal for receiving application of a second power supply voltage which varies to follow the first power supply voltage; an inverter unit configured to operate on the basis of the first power supply voltage, and to which a potential of the first node is input; and a signal outputting unit configured to output a power-on clear signal in accordance with an output of the inverter unit.