Power Enable Line Switching to Suppress IC Inrush Current
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Solution Overview
Problem
In semiconductor integrated circuit devices, high inrush currents can flow when power is turned on, generating power-supply noise and affecting other active circuit blocks.
Innovation Solution
A switch circuit configuration using pairs of transistors connected in parallel between power supply lines and ground lines, with buffer circuits controlling the transistors to manage the conductive state, allowing for gradual charging of the power supply line and reducing inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a power switch is inserted into a power supply line to shut off power, then power can be partially shut off to inactive circuit blocks, but high inrush current flows when the power switch is turned on, generating power-supply noise
Solution Approach 1:
The power switch is divided into a first power switch and a second power switch connected in parallel. The first power switch has a smaller switch element size and is turned on first to gradually charge the power supply line, while the second power switch has a larger switch element size and is turned on afterward. This segmentation of the switching function resolves the inrush current problem by distributing the charging current over time through multiple switches with different characteristics.
Solution Approach 2:
The first power switch is turned on in advance before the second power switch to preliminarily charge the power supply line. This preliminary action reduces the voltage difference that would otherwise cause a large inrush current when the main power switch is activated, thereby suppressing noise generation while maintaining the power management function.
2Speed
If the power switch is turned on quickly to restore power supply, then power is restored faster to circuit blocks, but high inrush current generates power-supply noise affecting other active circuit blocks
Solution Approach 1:
The power restoration process is segmented into two phases: first, the smaller first power switch is turned on to rapidly establish initial power supply; then the larger second power switch is turned on to complete the power restoration. This segmentation enables fast power recovery while controlling inrush current through the coordinated operation of switches with different sizes.
Solution Approach 2:
The first power switch, being smaller than the total required power capacity, provides partial power restoration initially. This partial action is sufficient to quickly reduce the voltage difference and suppress inrush current, after which the second power switch completes the full power restoration without generating excessive noise.
Data Source
AI summary
In the device, a pair of transistors includes first and second transistors connected in parallel between a power-supply-line and a power-supply or between a ground-line and a ground-potential. A third transistor is connected between the power-supply-line and the power-supply or between the ground-line and the ground-potential. First to third nodes are gate nodes of the first to third transistors. A first buffer outputs a first control-signal for controlling the first transistor. A second buffer is connected between the first node and the second and third nodes to receive the first control-signal and transmit a second control-signal for controlling the second and third transistors to the second and third nodes in parallel. When power-supplying starts, the second control signal drives the second and third transistors to the conductive-state after the first control-signal controls the first transistor to be driven in an intermediate-state between the conductive-state and a shutoff-state.