N-MOSFET Isolation for Touch Sensor and LED Driver Voltage Conflict
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Solution Overview
Problem
Combining LED drivers and touch sensors on a single IC chip poses challenges due to the different operating voltages required, where the higher voltage of the LED driver can affect the operation or damage the touch sensor circuit.
Innovation Solution
Incorporating an n-type field effect transistor (MOSFET) in series between the common node and the touch sensor circuit to electrically separate the operating voltages of the LED driver and touch sensor circuits, allowing the touch sensor to operate at a lower voltage while preventing the higher LED driver voltage from affecting it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If LED driver and touch sensor are combined on one IC chip with shared ports, then the size of the IC is reduced and the same port can be conveniently used with either the touch sensor or the LED driver, but the higher operating voltage of the LED driver may affect the operation of the touch sensor circuit and cause malfunction or damage
Solution Approach 1:
The patent divides the single shared port into two separate ports: a first port dedicated to the touch sensor circuit and a second port dedicated to the LED driver circuit. This segmentation allows each circuit to operate independently at its required voltage level without interference, resolving the contradiction between IC size reduction and circuit reliability.
Solution Approach 2:
The patent introduces a voltage translation circuit as an intermediary between the touch sensor circuit and the LED driver circuit. This intermediary translates the higher voltage from the LED driver to the lower voltage required by the touch sensor, enabling voltage compatibility while maintaining separate port operation and preventing damage to the touch sensor circuit.
2Power
If the LED driver operates at a higher voltage (3.0-4.3V) to drive the LED, then the LED can be driven effectively, but the higher operating voltage may affect the touch sensor circuit that operates at a lower voltage (1.65-1.95V)
Solution Approach 1:
The patent segments the voltage domains by providing separate ports for the touch sensor and LED driver. The touch sensor port operates at the lower voltage (1.65-1.95V) while the LED driver port operates at the higher voltage (3.0-4.3V), preventing high voltage interference from affecting the low voltage touch sensor circuit.
Solution Approach 2:
The voltage translation circuit serves as an intermediary that converts the higher LED driver voltage to the lower touch sensor voltage when needed. This intermediary ensures that the touch sensor circuit is protected from harmful high voltage effects while still enabling communication between the two circuits at different voltage levels.
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
This solution effectively isolates the touch sensor circuit from the higher operating voltage of the LED driver, preventing malfunctions and damage, thus enabling a combined touch sensor and LED driver IC without the issues of voltage interference.
Implementation Method 1
an n-type field effect transistor connected in series between the common node and the touch sensor. The n-type field effect transistor may be an n-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The present invention has the advantage that the higher operating voltage of the LED driver circuit is prevented from affecting the operation of the touch sensor circuit
Data Source
AI summary
A combined touch sensor and light-emitting-diode (LED) driver comprises a touch sensor circuit configured to detect a touch, where the touch sensor circuit is coupled to a common node and configured to operate with a first operating voltage, an LED driver circuit configured to drive an LED if the LED is coupled to the common node, where the LED driver circuit is also coupled to the common node and configured to operate with a second operating voltage is higher than the first operating voltage, and an n-type field effect transistor (FET) connected in series between the common node and the touch sensor. The n-type FET prevents the higher operating voltage of the LED driver from affecting the operation of the touch sensor, when a port of the combined touch sensor and LED driver IC is used to drive an LED. The touch sensor may be a capacitance-to-digital converter.