On-Chip LDO Power-Down Signal Generation for Touchscreen Controllers
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Solution Overview
Problem
Capacitive touchscreen controllers require low power consumption but need clean, ripple-free power, which often necessitates additional hardware for power down signals, increasing complexity and cost.
Innovation Solution
A touchscreen controller with an on-chip low drop-out regulator (LDO) and comparator that generates a power down signal based on the difference between input and regulated voltages, eliminating the need for additional pins or hardware by operating the LDO in off or on modes depending on the voltage threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an on-chip LDO is used to provide clean ripple-free power to the touchscreen controller, then power supply quality is improved, but power consumption increases
Solution Approach 1:
The LDO is configured to dynamically switch between on and off states based on real-time voltage difference detection. When the input voltage minus regulated voltage exceeds a threshold, the LDO turns on to provide clean power; when the difference is insufficient, it turns off to conserve power. This dynamic operation resolves the contradiction by adapting power supply quality to actual operational needs.
Solution Approach 2:
The system changes the operational state parameter of the LDO (on/off) based on voltage parameter thresholds. By monitoring the voltage difference and comparing it against a predetermined threshold, the system transitions the LDO between states, thereby adjusting power supply quality and consumption levels appropriately for different operating conditions.
2Use of energy by moving object
If an external pin is used to deliver power down signals to the touchscreen controller, then power savings are achieved, but hardware complexity increases
Solution Approach 1:
The touchscreen controller generates its own power down signal internally using the comparator to detect voltage differences. The comparator monitors the voltage difference between input and regulated outputs, and when the threshold is not met, automatically generates the power down signal to turn off the LDO. This self-service mechanism eliminates the need for external pins or additional control hardware, resolving the contradiction between power savings and hardware complexity.
Solution Approach 2:
The power down signal generation function is merged into the existing voltage regulation circuitry. The comparator that monitors voltage differences for LDO control is also used to generate the power down signal, combining multiple functions into a single integrated mechanism rather than requiring separate external control hardware.
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
Reduces hardware requirements and power consumption while maintaining reliable performance by internally generating the power down signal, enhancing efficiency and simplifying the touchscreen controller design.
Implementation Method 1
a first comparator configured to receive as first and second inputs thereto VSUPPLY and VDDA and to provide as an output therefrom a signal EN
Implementation Method 2
a first on-chip low drop out regulator (LDO) configured to receive and regulate as a first input thereto an input supply voltage (VSUPPLY), and to provide as an output therefrom a first regulated output voltage (VDDA)
Data Source
AI summary
Various embodiments of methods and devices are provided for a mutual capacitance touchscreen controller comprising a first on-chip low drop out regulator (LDO) configured to receive and regulate as a first input thereto an input supply voltage (VSUPPLY), and to provide as an output therefrom a first regulated output voltage (VDDA). A first comparator in the controller is configured to receive as first and second inputs thereto VSUPPLY and VDDA and to provide as an output therefrom a signal EN, EN being provided to the first LDO as a second input thereto. The first LDO is configured to operate in a first off mode and is turned off by signal EN when the difference between VSUPPLY and VDDA is less than a predetermined threshold.