Infineon KTY11-6 Silicon Temperature Sensor: Operational Principles and Application Circuits
The Infineon KTY11-6 is a highly reliable silicon-based temperature sensor known for its precision, linearity, and robust performance across a wide temperature range. Operating effectively from -50°C to +150°C, it is widely used in automotive, industrial, and consumer applications where accurate temperature monitoring is critical.
Operational Principles
The KTY11-6 operates based on the positive temperature coefficient (PTC) of silicon. As temperature increases, the resistance of the sensor increases in a predictable and nearly linear manner. This behavior stems from the intrinsic properties of silicon, where charge carrier mobility and density change with temperature. Unlike NTC thermistors, which exhibit exponential resistance change, the KTY11-6 offers a more linear response, simplifying circuit design and calibration.
Its characteristic curve is defined by a second-order polynomial, providing high accuracy. The typical resistance is approximately 1 kΩ at 25°C, with a sensitivity of around 7.5 Ω/°C near room temperature. This high sensitivity allows for precise temperature measurements with relatively simple signal conditioning circuits.
Application Circuits
1. Basic Voltage Divider Circuit:
The simplest method to interface the KTY11-6 is using a voltage divider. The sensor is connected in series with a fixed resistor (\(R_{series}\)), and the voltage at their junction is measured by an ADC. The value of \(R_{series}\) should be chosen close to the sensor's resistance at the midpoint of the desired temperature range to maximize sensitivity and linearity. This voltage output can be directly correlated to temperature using lookup tables or the sensor’s polynomial equation.
2. Operational Amplifier (Op-Amp) Interface:
For applications requiring better signal integrity or amplification, an op-amp can be employed in a non-inverting configuration. This setup buffers and amplifies the voltage from the divider, providing a stronger signal for measurement and improving noise immunity.
3. Wheatstone Bridge for High Precision:
In systems demanding high accuracy, such as automotive engine control units, a Wheatstone bridge configuration is used. The KTY11-6 forms one arm of the bridge. The bridge output is amplified by an instrumentation amplifier, providing excellent common-mode rejection and high resolution for small resistance changes.
4. Microcontroller-Based Linearization:
Although the KTY11-6 is relatively linear, software linearization can be implemented when connected to a microcontroller. The ADC reads the voltage, and the microcontroller applies the sensor’s polynomial equation (\(R_T = R_0 (1 + A \cdot T + B \cdot T^2)\)) to compute the temperature accurately, compensating for any minor non-linearity.
Advantages and Design Considerations
The key advantages of the KTY11-6 include its excellent long-term stability, high robustness against environmental factors, and reverse voltage protection. When designing circuits, ensure that the excitation current is low to avoid self-heating. Additionally, use precision resistors in the divider or bridge to maintain measurement accuracy. For noisy environments, filtering capacitors near the ADC input are recommended.
ICGOOODFIND: The Infineon KTY11-6 stands out for its superior linearity and reliability, making it ideal for critical temperature sensing tasks. Its simple interface and robust design ensure consistent performance in demanding applications.
Keywords: Temperature Sensor, Positive Temperature Coefficient, Signal Conditioning, Linearization, Robustness
