LDO Load Sharing Using Variable Dividers and External Pass Elements
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Solution Overview
Problem
LDO voltage regulators face issues with power dissipation, thermal management, and limited flexibility due to high load currents, which can damage the die and require complex thermal management solutions, while external pass elements offer less flexibility and lower bandwidth.
Innovation Solution
An LDO voltage regulator with integrated load sharing circuitry adaptively transfers load current between internal and external pass elements, using variable impedance dividers to adjust control signals and potentially a calibrated voltage source, allowing seamless load sharing and improved bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high load currents are handled by internal pass elements, then power dissipation and thermal management issues increase, but load handling capability is improved
Solution Approach 1:
The patent divides the load handling function between internal and external pass elements. The internal pass element handles light to moderate loads, while the external pass element handles heavy loads. This segmentation allows the internal circuitry to avoid excessive power dissipation and thermal issues while maintaining the ability to handle high load currents through the external element.
Solution Approach 2:
The patent extracts the heavy load handling function from the internal pass element and transfers it to an external pass element. The load sharing circuitry detects when the load exceeds a threshold and automatically transfers the excess current to the external pass element, thereby protecting the internal circuitry from thermal damage while maintaining high load capability.
2Area of stationary object
If external pass elements are used, then die area and thermal management needs are reduced, but bandwidth and flexibility decrease
Solution Approach 1:
The patent implements dynamic load sharing where the distribution of current between internal and external pass elements is not fixed but automatically adjusts based on load conditions. The load sharing circuitry continuously monitors the load and dynamically transfers current as needed, enabling the system to achieve both reduced die area and maintained bandwidth through adaptive operation rather than static configuration.
3Productivity
If internal pass elements handle all loads, then bandwidth is maintained, but power dissipation and thermal management complexity increase
Solution Approach 1:
The load sharing circuitry automatically monitors load conditions and self-adjusts the current distribution between internal and external pass elements without external intervention. When the load exceeds the optimal range for the internal pass element, the circuitry automatically transfers the excess current to the external pass element, thereby self-regulating power dissipation and thermal load while maintaining bandwidth.
Data Source
AI summary
Load sharing techniques for voltage regulators. In an example, the techniques may be implemented in an LDO voltage regulator configured to provide load sharing with a single driver for internal and external pass elements using a pair of variable voltage dividers to adjust the load sharing based on load current. In other examples, a calibrated voltage source can be used to replace one of the variable voltage dividers. Calibration circuitry and methodologies for determining the value of the calibrated voltage source are also described. In still other examples, a single variable voltage divider can be used, with no calibrated voltage source, by constraining the external pass element to be weaker than the internal pass element. In any such examples, the internal and external pass elements can be implemented, for instance, with either n-type or p-type power transistors, and with similar transistor technologies or diverse transistor technologies (e.g., FETs and BJTs).