LDO Regulator Internally Compensated ESR for Parasitic Resonance
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Solution Overview
Problem
Low dropout (LDO) linear regulators face instability due to parasitic elements in external circuits, which can cause resonance within the operating bandwidth, affecting the stability and noise resilience of the output voltage supply.
Innovation Solution
The implementation of an internally compensated effective series resistance (ESR) in the LDO regulator circuit, which includes a compensation circuit with current sense devices, driver circuits, and a filter, to isolate high-frequency resonance and stabilize the control loop without requiring external compensating circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external compensating circuitry is added to cancel parasitic effects, then the resilience to transient changes is improved, but the device complexity and component count increase
Solution Approach 1:
The patent combines the compensation function with the existing LDO regulator structure by integrating a series resistor within the control loop. This merging of functions allows the regulator to compensate for parasitic effects without requiring separate external compensating circuitry, thereby improving reliability while avoiding increased device complexity
Solution Approach 2:
The LDO regulator is designed to compensate for its own parasitic effects and those of external circuits through internal circuitry. The series resistor and associated control loop components work together to automatically cancel out the effects of parasitic inductance and capacitance, enabling the system to self-correct without external intervention
2Speed
If the control loop bandwidth is increased to improve transient response, then the frequency response to voltage transients is improved, but the stability margin decreases due to resonance from parasitic elements
Solution Approach 1:
The patent applies preliminary anti-action by introducing a series resistor that preemptively counteracts the harmful effects of parasitic inductance and capacitance before they can cause resonance. The resistor is specifically sized to cancel out the parasitic effects, creating a damping effect that prevents oscillations and maintains stability even at higher control loop bandwidths
Solution Approach 2:
The patent changes the electrical parameters of the control loop by introducing a series resistor with a specific resistance value. This parameter change modifies the loop impedance and damping characteristics, allowing the system to achieve both fast transient response and stable operation by optimizing the resistor value to match the parasitic elements
3Ease of manufacture
If flexible component selection and circuit board routing are allowed, then the ease of manufacture and installation is improved, but the parasitic elements and their harmful effects increase
Solution Approach 1:
The LDO regulator is designed to automatically compensate for parasitic effects regardless of their magnitude or source. The internal series resistor and control loop mechanism work together to self-correct for variations in parasitic inductance and capacitance caused by different component selections and board routing configurations, enabling manufacturing flexibility without sacrificing performance
Solution Approach 2:
The patent creates a universal compensation mechanism that handles multiple sources of parasitic effects (trace inductance, capacitor ESR, load variations) through a single integrated approach. The series resistor and control loop design provide multi-functional compensation that works across different application configurations, making the regulator adaptable to various component and routing choices
Data Source
AI summary
A voltage regulator circuit having an internally compensated effective series resistance includes a control circuit to generate an out current at a regulated output voltage based on a reference voltage. The control circuit includes an amplifier, a resistive element to feedback output voltage to an input of the amplifier, and a compensation circuit to couple the internally compensated effective series resistance into the control circuit. The compensation circuit includes a first current sense device to generate a first sensed current proportional to a current through an N-type pass device, a second current sense device arranged to generate a second sensed current proportional to the current through the N-type pass device, and a bias circuit coupled to sink the first sensed current and the second sensed current to reduce a bias voltage across the resistive element below a threshold voltage.