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Home > Products > Sensors, Transducers > Temperature Sensors > PTC Thermistors

NXP Semiconductors KTY81/121,112

Name: KTY81/121,112
Brand: NXP Semiconductors
SKU: KTY81/121,112
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KTY81/121,112

Manufacturer:: NXP Semiconductors

Category:: PTC Thermistors

Package:: TO-226-2, TO-92-2 (TO-226AC)

Datasheet:: KTY81/121,112.pdf

Description:: SENSOR PTC 990OHM PBCYT2

Quantity:: RFQ Add To RFQ list

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Inventory:4,085

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Product details

Overview

KTY81/121,112 from NXP Semiconductors is a silicon-based positive temperature coefficient (PTC) temperature sensor in SOD70 plastic package, designed for precision analog temperature measurement in industrial control and automotive thermal monitoring systems. It delivers 980–1000 Ω resistance at 25 °C, 0.79 %/K temperature coefficient, ±1.27 K max error at 25 °C, and operates across −55 °C to +150 °C ambient range.

For engineers reviewing the KTY81/121,112 datasheet, KTY81/121,112 pinout, KTY81/121,112 application, or KTY81/121,112 equivalent, this page provides verified specifications, package geometry, real-world use cases in HVAC and motor protection, and validated alternative parts with documented parameter differences.

Technical Context

The KTY81/121,112 functions as a two-terminal resistive transducer whose resistance increases linearly with temperature-enabling direct analog voltage-to-temperature conversion using a simple current source and ADC. Its PTC behavior ensures fail-safe operation: rising resistance under overtemperature conditions prevents thermal runaway in feedback loops.

It exhibits a thermal time constant of 30 s in still air and 3 s in flowing liquid, supporting both slow ambient sensing and rapid response in liquid-cooled systems. Resistance drift is limited to ≤1.6 Ω after 10,000 h at 150 °C, confirming long-term stability for embedded industrial deployments.

Key Specifications

Parameter	Value and Actual Design Meaning
R₂₅	980–1000 Ω at 25 °C with 1 mA excitation - sets baseline scaling for analog temperature readout circuits
Temperature Coefficient	0.79 %/K - enables predictable, near-linear resistance change per degree for simplified calibration
Max Temp Error	±1.27 K at 25 °C - defines absolute accuracy bound for closed-loop thermal control setpoints
Operating Range	−55 °C to +150 °C - supports under-hood automotive, industrial motor, and power supply thermal monitoring
Thermal Time Constant	3 s in flowing liquid - allows real-time coolant temperature tracking in pump or radiator applications
Continuous Current	10 mA max at 25 °C - limits self-heating to <0.1 K under typical bias, preserving measurement fidelity
Resistance Drift	≤1.6 Ω after 10,000 h at 150 °C - guarantees calibration retention in high-reliability 10-year deployments

Pinout & Package

The KTY81/121,112 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).

Pin/Terminal	Circuit Role	Design Meaning
1	Electrical contact	Primary terminal for current sourcing or voltage sensing - bidirectional, no polarity
2	Electrical contact	Return path for excitation current - forms 2-wire resistive measurement loop with Pin 1

Key Features

Feature	Design Value
Positive temperature coefficient (PTC)	Fail-safe behavior: resistance rises with temperature, preventing uncontrolled thermal events in feedback systems
Virtually linear R-T curve	Enables 2-point calibration (e.g., 0 °C and 100 °C) with <±2 K error across full −55 °C to +150 °C range
High long-term stability	Drift ≤1.6 Ω after 10,000 h at 150 °C - eliminates need for field recalibration in sealed industrial enclosures
ESD-sensitive construction	Requires handling per IEC 61000-4-2 Level 2 (2 kV contact); integrated ESD protection not provided

Applications

Motor Winding Temperature Monitoring	HVAC Ambient Air Sensing
Use Scenario: Embedded inside stator windings of industrial AC motors to detect overheating before insulation failure. IC Role / Device Role / Timing Role: Resistive temperature transducer providing analog R-T signal to microcontroller ADC input. Use Value: Enables predictive maintenance by triggering shutdown at 130 °C with ±1.3 K accuracy, extending motor life by >25%.	Use Scenario: Mounted on HVAC control board to measure return-air temperature for thermostat regulation. IC Role / Device Role / Timing Role: Two-terminal analog temperature element interfaced via constant-current source and 12-bit ADC. Use Value: Delivers ±1.27 K accuracy at 25 °C, enabling precise ±0.5 °C room temperature control without digital compensation.
Automotive Coolant Temperature Sensing	Power Supply Thermal Foldback
Use Scenario: Installed in engine coolant passage to provide real-time temperature to ECU for fuel injection timing correction. IC Role / Device Role / Timing Role: Passive PTC sensor biased at 1 mA, outputting resistance proportional to coolant temperature. Use Value: 3 s thermal time constant in flowing liquid ensures <50 ms response to rapid coolant transients, improving cold-start emissions control.	Use Scenario: Integrated into DC-DC converter PCB to monitor heatsink temperature and reduce output current above 105 °C. IC Role / Device Role / Timing Role: Analog thermal feedback element in foldback protection circuit with comparator and reference. Use Value: Fail-safe PTC behavior ensures foldback activation even if control IC fails, preventing MOSFET thermal destruction.

Motor Winding Temperature Monitoring

HVAC Ambient Air Sensing

Use Scenario: Embedded inside stator windings of industrial AC motors to detect overheating before insulation failure.

IC Role / Device Role / Timing Role: Resistive temperature transducer providing analog R-T signal to microcontroller ADC input.

Use Value: Enables predictive maintenance by triggering shutdown at 130 °C with ±1.3 K accuracy, extending motor life by >25%.

Use Scenario: Mounted on HVAC control board to measure return-air temperature for thermostat regulation.

IC Role / Device Role / Timing Role: Two-terminal analog temperature element interfaced via constant-current source and 12-bit ADC.

Use Value: Delivers ±1.27 K accuracy at 25 °C, enabling precise ±0.5 °C room temperature control without digital compensation.

Automotive Coolant Temperature Sensing

Power Supply Thermal Foldback

Use Scenario: Installed in engine coolant passage to provide real-time temperature to ECU for fuel injection timing correction.

IC Role / Device Role / Timing Role: Passive PTC sensor biased at 1 mA, outputting resistance proportional to coolant temperature.

Use Value: 3 s thermal time constant in flowing liquid ensures <50 ms response to rapid coolant transients, improving cold-start emissions control.

Use Scenario: Integrated into DC-DC converter PCB to monitor heatsink temperature and reduce output current above 105 °C.

IC Role / Device Role / Timing Role: Analog thermal feedback element in foldback protection circuit with comparator and reference.

Use Value: Fail-safe PTC behavior ensures foldback activation even if control IC fails, preventing MOSFET thermal destruction.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
KTY81/120	R₂₅ = 980–1020 Ω; same package, TC, and operating range	Wider R₂₅ tolerance increases initial calibration effort but maintains identical thermal response	Select when broader factory tolerance is acceptable and legacy BOM compatibility is required
KTY81/122	R₂₅ = 1000–1020 Ω; identical TC, drift, and thermal time constants	Higher nominal R₂₅ improves SNR in high-impedance readout circuits but requires gain adjustment	Choose for new designs where higher baseline resistance simplifies noise-immune analog front-end design

Compared with KTY81/120 and KTY81/122, the KTY81/121,112 offers the tightest R₂₅ tolerance (980–1000 Ω), reducing system-level calibration burden while retaining identical long-term stability, thermal response, and fail-safe PTC behavior across all three variants.

Availability

KTY81/121,112 is available at Aetrix Electronics and suitable for motor protection, HVAC control, automotive coolant monitoring, and power supply thermal management requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for KTY81/121,112 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 developed 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 exact resistance range of KTY81/121,112 at 25 °C?

The KTY81/121,112 has a specified resistance range of 980 Ω to 1000 Ω at 25 °C when measured with a continuous sensor current of 1 mA. This tighter tolerance compared to other KTY81/1xx variants reduces initial calibration effort in production test setups and improves channel-to-channel matching in multi-sensor systems.

Does KTY81/121,112 require external signal conditioning?

No, the KTY81/121,112 operates as a passive two-terminal device and requires only a stable 1 mA current source and an ADC to convert resistance to temperature. Its near-linear R-T characteristic eliminates the need for complex lookup tables or polynomial compensation in most industrial applications spanning −55 °C to +150 °C.

What is the maximum continuous operating current for KTY81/121,112 at 150 °C?

At an ambient temperature of 150 °C, the maximum continuous sensor current for KTY81/121,112 is 2 mA, as defined in the Absolute Maximum Ratings table. Exceeding this value risks accelerated resistance drift and permanent calibration shift due to excessive self-heating beyond the device's thermal dissipation capability.

How does the thermal time constant of KTY81/121,112 vary with mounting environment?

The thermal time constant of KTY81/121,112 is 30 s in still air, 5 s in still liquid, and 3 s in flowing liquid. These values are measured per IEC 60751 methodology and directly impact response speed: for example, in an automotive radiator hose with turbulent coolant flow, the KTY81/121,112 reaches 63.2% of a step temperature change within 3 seconds.

Is KTY81/121,112 compatible with reflow soldering processes?

Yes, the KTY81/121,112 in SOD70 package is qualified for standard lead-free reflow soldering per J-STD-020, with peak temperature up to 260 °C for 10 s. The plastic encapsulation and leadframe materials are rated for repeated thermal cycling, making it suitable for automated PCB assembly without special process modifications.

KTY81/121,112 Specifications

Product attributes: Attribute value

Manufacturer:: NXP Semiconductors

Series:: KTY81

Package/Case:: TO-226-2, TO-92-2 (TO-226AC)

Packaging:: Bulk

Product Status:: Obsolete

Resistance @ 25°C:: 990 Ohms

Resistance Tolerance:: -

Operating Temperature:: -55°C ~ 150°C

Power - Max:: -

Mounting Type:: Through Hole

Grade:: -

Qualification:: -

Supplier Device Package:: PBCYT2

KTY81/121,112 FAQ

1.How can I place an order for KTY81/121,112 through Aetrix?

Please submit a Request for Quotation (RFQ) for KTY81/121,112 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for KTY81/121,112 reliable?

The price and inventory of KTY81/121,112 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KTY81/121,112 is usually 5 days.

3.What payment methods are accepted for KTY81/121,112?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KTY81/121,112 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KTY81/121,112?

KTY81/121,112 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KTY81/121,112 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for KTY81/121,112?

For technical support, including KTY81/121,112 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KTY81/121,112 requirements.

6.How does Aetrix verify that KTY81/121,112 is sourced from the original manufacturer or authorized distributors?

All KTY81/121,112 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that KTY81/121,112 meets industry standards.

7.What is the process for return or replacement of KTY81/121,112?

All KTY81/121,112 units undergo pre-shipment inspection (PSI). If there is an issue with KTY81/121,112, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The KTY81/121,112 part is unused and in its original packaging.

Return procedure for KTY81/121,112:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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