Capacitor-Less LDO Pole-Zero Tracking Frequency Compensation
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Solution Overview
Problem
Conventional LDO regulators fail to provide improved transient performance and power-efficiency over a wide load current range, especially in Sea-of-Gates applications, due to inadequate handling of dynamic and leakage currents, and cannot support low-power operation modes effectively.
Innovation Solution
A capacitor-less low-dropout (CL-LDO) regulator architecture with a pole-zero tracking frequency compensation method, utilizing two pass-devices (M1 and M2) in parallel, where M1 addresses fast load current variations and M2 handles slow variations, along with two closed-loop structures for feedback control, maintaining a fixed quiescent current level and directing excess low-frequency currents to M2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDO regulator is used, then the circuit is simple and small in size, but the transient performance and power-efficiency are inadequate over a wide load current range
Solution Approach 1:
The patent divides the single pass-device into two parallel pass-devices (first and second pass-devices) with different sizes, where the first pass-device handles fast load current variations and the second pass-device handles slow load current variations. This segmentation allows each device to be optimized for specific frequency ranges, improving transient performance without requiring a completely complex redesign of the entire regulator
2Adaptability or versatility
If a single pass-device is used, then the device complexity is low, but the regulator cannot effectively handle both fast and slow load current variations
Solution Approach 1:
The patent assigns different functional characteristics to different pass-devices: the first pass-device is sized and configured to respond to fast transient changes, while the second pass-device is sized to handle slow variations and leakage currents. This local differentiation of device properties enables the system to adapt to a wide range of load conditions without requiring a single overly complex device
3Stability of the object's composition
If conventional frequency compensation is used, then the design is simple, but stability cannot be maintained across varying load currents and temperatures
Solution Approach 1:
The patent implements dynamic frequency compensation where the dominant pole frequency is made variable through the dual-pass-device configuration. As load conditions change, the effective pole locations shift dynamically to maintain optimal phase margin and stability. The control circuit adjusts the compensation characteristics based on the operating point, allowing the regulator to remain stable across varying load currents and temperatures without requiring complex fixed compensation networks
4Use of energy by moving object
If power-gating techniques are used to extend load range, then power-efficiency improves, but the regulator cannot satisfy the extended load range requirements
Solution Approach 1:
The patent segments the load current handling between two pass-devices, allowing the first pass-device to be turned off or gated during low-power modes while the second pass-device maintains regulation. This segmentation enables power-gating techniques to be effectively applied, extending the load range down to very low currents while maintaining power-efficiency, as each device can be independently controlled based on the operating conditions
Data Source
AI summary
An electronic device may include: a load and a voltage regulator coupled to the load and configured to provide a load current, where the voltage regulator includes a first and a second pass device coupled in parallel and configured to operate simultaneously. A method may include providing current to a load using a first and a second pass device coupled in parallel and configured to operate simultaneously, where the first device provides a first current corresponding to a high-frequency component and the second device provides a second current corresponding to a low-frequency component; in response to a decrease in a low-frequency component, causing the second current to decrease and causing the low-frequency component to increase; and in response to an increase in the low-frequency component, causing the second current to increase and causing the low-frequency component to decrease.