NXP Semiconductors KTY81/120,112

Overview

KTY81/120,112 from NXP Semiconductors is a silicon-based positive temperature coefficient (PTC) temperature sensor in SOD70 plastic package, with nominal resistance of 1000 Ω at 25 °C, ±0.79 %/K temperature coefficient, and operating range from −55 °C to +150 °C. It delivers linear resistance vs. temperature behavior for precision thermal monitoring in HVAC control circuits, motor winding protection, and power supply thermal regulation.

For engineers reviewing the KTY81/120,112 datasheet, KTY81/120,112 pinout, KTY81/120,112 application, or KTY81/120,112 equivalent, this page provides verified specifications, package geometry, real-world use scenarios, and validated alternative parts for thermal sensing design-in and BOM optimization.

Technical Context

The KTY81/120,112 operates as a two-terminal passive resistive sensor requiring external bias current (typically 1 mA) to generate voltage proportional to temperature. Its PTC response is inherently fail-safe-resistance increases with overtemperature, enabling direct integration into comparator-based shutdown circuits without active signal conditioning.

Resistance variation follows a well-characterized polynomial curve across −55 °C to +150 °C, with maximum temperature error of ±2.54 K at 25 °C and ±5.05 K at 100 °C under 1 mA excitation. Thermal time constant is 30 s in still air and 3 s in flowing liquid, defining dynamic response limits in closed-loop thermal management systems.

Key Specifications

Pinout & Package

The KTY81/120,112 is housed in a SOD70 plastic near-cylindrical single-ended package with two in-line leads. Dimensions: 4.4–4.8 mm body width, 5.0–5.2 mm height, 3.6–4.2 mm thickness, 2.54 mm lead pitch (bulk) or 5.08 mm (reel, spread leads).

Key Features

Applications

Equivalent & Alternatives

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

Compared with KTY81/120,112, KTY81/121 offers tighter high-end resistance control for improved cold-range linearity, while KTY81/122 shifts nominal R₂₅ upward to reduce bias current demand-both retain identical SOD70 packaging, thermal specs, and PTC behavior.

Availability

KTY81/120,112 is available at Aetrix Electronics and suitable for HVAC control systems, motor protection circuits, and power supply thermal regulation requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for KTY81/120,112 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The KTY81 series was designed by NXP specifically for high-reliability analog temperature sensing in harsh environments, emphasizing long-term stability, fail-safe PTC behavior, and compatibility with standard PCB assembly processes.

FAQ

What is the nominal resistance of KTY81/120,112 at 25 °C?

The KTY81/120,112 has a specified resistance range of 980 Ω to 1020 Ω at 25 °C, with 1000 Ω as the typical value. This tolerance window is defined under 1 mA continuous sensor current and is critical for setting gain and offset in analog signal chains. The KTY81/120,112's R₂₅ directly impacts absolute temperature accuracy and must be characterized per unit during system calibration.

Does KTY81/120,112 require polarity-aware connection?

No, the KTY81/120,112 is a two-terminal passive resistor with no polarity. Pins 1 and 2 are electrically identical electrical contacts; either may connect to the bias current source or measurement node. This simplifies PCB layout and eliminates risk of reverse installation. The KTY81/120,112 functions identically regardless of orientation in the circuit.

What is the maximum continuous operating current for KTY81/120,112?

The KTY81/120,112 supports up to 10 mA continuous current at 25 °C ambient, but derates to 2 mA at 150 °C to limit self-heating error. Operating above these limits risks permanent resistance drift. For stable measurements, NXP recommends 1 mA excitation-this value is used throughout the KTY81/120,112's published R–T tables and error specifications.

How does the temperature coefficient of KTY81/120,112 affect measurement linearity?

The KTY81/120,112 exhibits a typical temperature coefficient of 0.79 %/K, which yields near-linear resistance change across −20 °C to +100 °C. While not perfectly linear, its deviation remains within ±0.2 % of ideal linearity in that range-enabling simple linear interpolation in firmware. The KTY81/120,112's R–T behavior is more predictable than NTC thermistors, reducing calibration complexity.

Is KTY81/120,112 compatible with reflow soldering processes?

Yes, the KTY81/120,112 in SOD70 package is qualified for standard Pb-free reflow profiles (JEDEC J-STD-020), with peak temperature up to 260 °C for 10 s. Its plastic encapsulation withstands thermal cycling without delamination. However, due to ESD sensitivity, post-reflow handling must follow ANSI/ESD S20.20 guidelines-grounded workstations and ionized airflow are required when manually placing or inspecting the KTY81/120,112.