LDO Load Sharing Using Variable Dividers for Bandwidth and Heat
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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 regulators suffer from low bandwidth and inflexibility.
Innovation Solution
An LDO voltage regulator system with integrated and external pass elements that adaptively share load current using load sharing circuitry, allowing seamless transfer between internal and external pass elements, with control signals from an error amplifier and variable impedance dividers, enabling efficient load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high load current is handled by internal pass element, then power dissipation and thermal management issues occur, but using external pass element introduces low bandwidth and inflexibility
Solution Approach 1:
The load current handling function is segmented between internal and external pass elements. The internal pass element handles low to medium load currents, while the external pass element handles high load currents. This segmentation allows the system to distribute power dissipation across multiple components, reducing thermal management requirements while maintaining system flexibility and bandwidth through the internal pass element's continued operation.
2Area of stationary object
If only internal pass element is used, then die area and thermal management complexity increase for high loads, but external pass element alone lacks flexibility and bandwidth
Solution Approach 1:
The system segments the pass element functionality between internal and external components. The internal pass element remains on-chip with minimal die area, while the external pass element handles high current loads off-chip. This segmentation reduces the required die area for high load handling while preserving system flexibility through the internal pass element's continued operation and adaptive load sharing capability.
Solution Approach 2:
The load sharing circuit acts as an intermediary that dynamically controls the distribution of load current between internal and external pass elements. This intermediary circuit enables seamless transition and cooperative operation, allowing the system to leverage both internal and external pass elements according to load conditions, thereby reducing die area requirements while maintaining flexibility.
3Temperature
If external pass element is used for high load current, then thermal management needs are reduced, but system bandwidth and response time decrease
Solution Approach 1:
The system segments the operational responsibilities between internal and external pass elements based on load current levels. The internal pass element handles low to medium loads where high bandwidth and fast response are critical, while the external pass element handles high loads where thermal management becomes the primary concern. This segmentation allows the system to optimize for speed when needed and for thermal management when required.
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).