LDO Voltage Regulator Fast Shutdown via Discharge Transistor
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Solution Overview
Problem
Conventional low drop-out (LDO) voltage regulators require large electrostatic discharge (ESD) devices for fast shutdown, which can impede ESD performance and occupy significant area, posing a bottleneck in shutdown operations.
Innovation Solution
A voltage regulator design incorporating a differential amplifier, output transistor, shutdown control unit, and discharge transistor with a resistor-based voltage feedback circuit, where the discharge transistor is coupled through a resistor to the output terminal, serving as both an ESD protection and enabling fast shutdown without the need for a separate large ESD device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a large area ESD device is used for fast shutdown in conventional LDO regulators, then shutdown speed is improved, but device area and ESD performance deteriorate
Solution Approach 1:
The patent combines the ESD protection function and fast shutdown function into a single discharge transistor structure. The discharge transistor's first terminal connects to the output terminal and its second terminal connects to ground, allowing it to serve dual purposes: protecting against electrostatic discharge and enabling rapid shutdown. This eliminates the need for separate large-area ESD devices while maintaining fast shutdown capability.
Solution Approach 2:
The discharge transistor is designed to perform multiple functions simultaneously: ESD protection and fast shutdown control. By making this single component universal, the patent resolves the contradiction by eliminating the need for dedicated large-area ESD devices, thereby reducing overall device area while maintaining both ESD protection and fast shutdown performance.
2Ease of operation
If a large area ESD device is used for fast shutdown, then shutdown capability is improved, but ESD performance deteriorates
Solution Approach 1:
The patent merges the ESD protection path and fast shutdown path into a single discharge transistor structure. This unified structure ensures that the same component that provides fast shutdown also provides ESD protection, eliminating the performance bottleneck caused by separate large-area ESD devices and maintaining reliable ESD performance.
Solution Approach 2:
The discharge transistor serves as a universal component for both ESD protection and fast shutdown operations. This multi-functionality ensures that ESD performance is not compromised by the presence of large-area dedicated ESD devices, while still providing effective shutdown capability.
3Reliability
If separate ESD protection devices are added, then ESD performance is improved, but device complexity and area increase
Solution Approach 1:
The patent combines ESD protection functionality with the existing fast shutdown discharge transistor, eliminating the need for separate ESD protection devices. This merging approach reduces device complexity and component count while maintaining reliable ESD performance through the multi-functional discharge transistor structure.
Data Source
AI summary
Voltage regulators are provided. In one embodiment of the voltage regulators, a differential amplifier receives a reference voltage and a feedback voltage, to generate a control signal according to a voltage difference between the feedback voltage and the reference voltage. An output transistor has a first terminal coupled to a power voltage, a control terminal coupled to the differential amplifier for receiving the control signal, and a second terminal coupled to an output terminal. A voltage feedback circuit is coupled between the output terminal and a ground voltage to generate the feedback voltage. A discharge transistor has a first terminal coupled to the ground voltage, a control terminal coupled to a first control signal, and a second terminal coupled to the output terminal through a first resistor in the voltage feedback circuit.