Infineon Technologies KTY135

Overview

KTY135 from Infineon Technologies is a silicon-based positive temperature coefficient (PTC) temperature sensor in SOT-23 package, designed for precision analog temperature sensing in automotive and industrial control loops. It exhibits R₂₅ = 2000 Ω ±3%, operates from −50 °C to +150 °C, delivers linearized resistance vs. temperature response via second-order polynomial (α = 7.88×10⁻³ K⁻¹, β = 1.937×10⁻⁵ K⁻²), and is used in engine coolant monitoring and motor winding thermal protection.

For engineers reviewing the KTY135 datasheet, KTY135 pinout, KTY135 application, or KTY135 equivalent, this page provides verified electrical characteristics, validated SOT-23 terminal mapping, confirmed thermal time constant (τ_air = 7 s), and real-world substitution guidance for PTC-based analog temperature measurement circuits.

Technical Context

The KTY135 implements a planar n-conducting silicon crystal element with symmetrical construction enabling polarity-independent operation. Its resistance–temperature behavior follows RT = R₂₅ × (1 + α·ΔT + β·ΔT²) over −30 °C to +130 °C, yielding calculable temperature resolution better than ±0.5 °C within that range when paired with 1 mA excitation current.

It requires no external calibration due to inherent long-term stability and specified R₂₅ tolerance (±3%). Thermal response is characterized by τ_air = 7 s and τ_oil = 1 s, supporting fast transient detection in liquid-cooled systems while maintaining robustness against induced voltage spikes via recommended >10 nF parallel decoupling.

Key Specifications

Pinout & Package

SOT-23 package with two-terminal configuration: symmetrical, polarity-independent device requiring no orientation during placement.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PTC temperature sensing applications.

Compared with KTY135, KTY136 offers improved initial accuracy at higher cost, while KTY235 reduces voltage burden but requires gain adjustment in signal chain - both retain identical thermal response and packaging.

Availability

KTY135 is available at Aetrix Electronics and suitable for engine management systems, motor drive thermal protection, inverter capacitor monitoring, and industrial oven control requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for KTY135 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Infineon Technologies is a German semiconductor manufacturer specializing in power management, automotive ICs, and sensor solutions with global manufacturing and quality certification (IATF 16949, ISO 9001).

The KTY-series was developed specifically for high-reliability analog temperature sensing in harsh environments, targeting automotive powertrain, industrial motor control, and renewable energy systems where silicon PTC linearity and stability outperform thermistors.

FAQ

What is the correct excitation current for KTY135?

The KTY135 is characterized at I_op = 1 mA, which minimizes self-heating (<0.1 °C error) while ensuring sufficient signal level. Operating between 0.5 mA and 5 mA is permissible, but currents above 5 mA require pulse-width limitation per absolute maximum ratings (7 mA continuous, 10 mA peak for ≤10 ms).

Can KTY135 be used in a Wheatstone bridge configuration?

Yes - its symmetrical two-terminal construction and predictable R–T curve make it suitable as one arm of a Wheatstone bridge. For best common-mode rejection, pair it with a matched fixed resistor or another KTY device; bridge output scales linearly with temperature when excited at constant current.

Does KTY135 require external calibration?

No - the device ships with factory-trimmed R₂₅ and guaranteed TCR coefficients (α, β). Full temperature reconstruction is possible using the published second-order equation without individual unit calibration, provided excitation current is stable and lead resistance is compensated.

How does self-heating affect KTY135 accuracy in still air?

At 1 mA excitation, self-heating in still air is <0.1 °C. At 5 mA, self-heating rises to ~2.5 °C - exceeding typical accuracy requirements. Therefore, 1 mA is recommended for static air measurements; forced airflow or oil immersion further suppresses self-heating effects.