On-Chip LDO Voltage Regulator Calibration System
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Solution Overview
Problem
Integrated circuits with CMOS technology suffer from performance degradation due to inherent input offset in voltage monitors, requiring time-consuming and costly trimming processes using automatic test equipment, which cannot be performed post-production.
Innovation Solution
An on-chip calibration system for low dropout (LDO) voltage regulators, incorporating a comparator, successive approximation register (SAR) circuit, resistor string, control circuit, voltage sensing circuit, and single-pole double-throw (SPDT) switch, allows for real-time monitoring and automatic trimming of the voltage regulator output, compensating for changes in load current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If trimming is performed using automatic test equipment (ATE) during production testing, then the voltage monitor accuracy is improved by removing inherent input offset, but the production testing time increases significantly
Solution Approach 1:
The voltage monitor circuit performs self-trimming by using its own output signal and internal resources. The circuit monitors its own output voltage, compares it against a reference, and automatically adjusts the trim code through feedback control without requiring external ATE instrumentation, thereby eliminating the time-consuming external trimming process while maintaining accuracy
Solution Approach 2:
The invention implements a feedback mechanism where the voltage monitor's output is continuously monitored and compared against a reference voltage. Based on the comparison result, the circuit automatically adjusts the trim code to compensate for input offset, creating a closed-loop system that improves accuracy without requiring external testing equipment
2Measurement precision
If multiple voltage monitors are trimmed during production testing, then the accuracy of each monitor is improved, but the total testing time increases even longer
Solution Approach 1:
Each voltage monitor circuit is equipped with self-trimming capability using its own output signal and internal resources. This eliminates the need for external ATE to sequentially trim each monitor, allowing multiple monitors to be trimmed simultaneously or independently without increasing overall testing time, thereby improving both accuracy and productivity
3Productivity
If LDO regulator is trimmed at just one load condition during production testing, then the trimming process is simplified and faster, but the trim code accuracy deteriorates for other load conditions
Solution Approach 1:
The invention implements dynamic trimming that adapts to different load conditions. The circuit continuously monitors the output voltage under varying load conditions and automatically adjusts the trim code in real-time to maintain optimal accuracy across all operating conditions, transforming the static single-point trimming into a dynamic multi-condition optimization process
Solution Approach 2:
The circuit changes the operating parameters by monitoring output voltage across different load conditions and adjusting the trim code accordingly. This allows the system to optimize performance for each specific load condition rather than relying on a single trim code derived from one condition, thereby maintaining high accuracy across the full operating range
4Measurement precision
If on-chip calibration system is implemented for real-time monitoring and automatic trimming, then the accuracy and adaptability are improved, but the device complexity increases
Solution Approach 1:
The invention merges the calibration functionality with the existing voltage monitor circuit by utilizing its output signal and integrating the trimming logic within the same chip. This consolidation approach implements real-time monitoring and automatic trimming without requiring separate external calibration equipment, thereby improving accuracy while minimizing the increase in device complexity through resource sharing and integration
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient and cost-effective on-chip trimming of LDO regulators, improving accuracy and reducing production testing time by allowing continuous monitoring and adjustment of output voltage, even after the IC is released.
Implementation Method 1
a comparator, successive approximation register (SAR) circuit
Implementation Method 2
voltage sensing circuit has a first input coupled to a reference voltage, a second input coupled to the output of the LDO regulator circuit
Data Source
AI summary
An integrated circuit includes a voltage monitor circuit having a first input coupled to a reference voltage and a second input, a successive approximation register (SAR) circuit having an input coupled to an output of the voltage monitor circuit, a low drop out (LDO) regulator having an input coupled to an output of the SAR circuit and an output coupled to the second input, a discharge circuit coupled to the LDO output, voltage sensing circuit having a first input coupled to the reference voltage during a trim mode and coupled to the LDO output during a monitor mode, having a second input coupled to the reference voltage, and an output which asserts a sense indicator that indicates when a voltage at the first input goes higher or lower than the reference voltage by a predetermined amount. Control circuitry is configured to, during trim mode, periodically discharge the LDO output voltage.