Dual-Mode LDO Circuit for Fast Transient Mode Switching
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Solution Overview
Problem
Existing voltage regulator circuits face limitations in accurately sensing low load currents due to the finite resolution of analog-to-digital converters (ADCs) and the inherent limitations of current sensing methods like series resistive elements and current mirror circuits.
Innovation Solution
A dual mode, low dropout regulator circuit is introduced, featuring a multiplexer for switching between high-speed and low-power modes, an error amplifier for generating an amplifier output, and a class AB circuit with a unity feedback configuration to enable efficient dual mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a series resistive element is used to sense load current, then the voltage drop can be measured using an ADC, but the minimum detectable current is limited by the ADC's finite resolution
Solution Approach 1:
The patent divides the voltage regulation into two segments: a first voltage regulator for high current modes and a second voltage regulator for low current modes. This segmentation allows each regulator to be optimized for its specific current range, with the second regulator capable of accurately sensing very low currents that would be below the ADC resolution limit when measured by a single regulator design.
Solution Approach 2:
The patent implements dynamic switching between two voltage regulator configurations based on the operating current level. A controller selectively activates the first or second voltage regulator depending on whether the load current is above or below a threshold, enabling the system to adapt its measurement and regulation capability to the actual operating conditions.
2Measurement precision
If a current mirror circuit is used to sense load current, then the mirrored current can be dumped on a resistor for ADC sensing, but the sensing accuracy is still limited by ADC resolution
Solution Approach 1:
The patent segments the current sensing function into two parallel paths: one using a current mirror with a first resistor for high current measurement, and another using a second resistor for low current measurement. Each path is activated depending on the operating mode, allowing accurate sensing across the full current range despite ADC resolution limitations.
Solution Approach 2:
The patent creates a universal current sensing system that can accurately measure both high and low currents by providing two different sensing configurations. The system universally handles the full range of current values by selecting the appropriate sensing path, making the ADC resolution limitation irrelevant across the entire operating range.
3Device complexity
If a common mode LDO is used to supply both high-speed and low-power modes, then power supply is simplified, but IR drops and bandwidth limitations occur
Solution Approach 1:
The patent segments the power supply into two independent voltage regulators: a first voltage regulator dedicated to high-speed mode operation and a second voltage regulator dedicated to low-power mode operation. This eliminates the need for a common mode LDO and prevents IR drops from affecting both modes simultaneously, as each regulator independently supplies its designated mode.
Solution Approach 2:
The patent applies local quality by providing different power supply characteristics optimized for each operating mode. The first voltage regulator is optimized for high-current, high-speed operation while the second is optimized for low-current, low-power operation, allowing each mode to receive power supply characteristics tailored to its specific requirements rather than a compromise common supply.
4Device complexity
If a single voltage regulator is used for both high-speed and low-power modes, then device complexity is reduced, but fast transient switching between modes is not achieved
Solution Approach 1:
The patent segments the voltage regulation function into two separate regulators that can operate independently. This allows the controller to rapidly switch between them based on mode requirements, achieving fast transient response because each regulator is already optimized and ready for its specific mode rather than requiring a single regulator to reconfigure.
Solution Approach 2:
The patent implements preliminary action by pre-configuring two voltage regulators with their respective optimized parameters before mode switching is needed. The first regulator is pre-configured for high-speed operation and the second for low-power operation, so when mode switching occurs, the transition is rapid because the appropriate regulator is already prepared and can be immediately activated.
Data Source
AI summary
The present disclosure relates to a dual mode, low dropout regulator circuit and method of using the same. The circuit may include a multiplexer configured to switch between a high-speed mode and a low-power mode and an error amplifier configured to generate an amplifier output. The circuit may include a class AB circuit configured to receive the amplifier output and generate a class AB output and a unity feedback circuit in electrical communication with the class AB circuit, wherein a single reference voltage is applied to perform a dual mode operation.