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

NXP Semiconductors KTY81/221,112

Name: KTY81/221,112
Brand: NXP Semiconductors
SKU: KTY81/221,112
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KTY81/221,112

Manufacturer:: NXP Semiconductors

Category:: PTC Thermistors

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

Datasheet:: KTY81/221,112.pdf

Description:: SENSOR PTC 1.98KOHM PBCYT2

Quantity:: RFQ Add To RFQ list

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Product details

Overview

KTY81/221,112 from NXP Semiconductors is a silicon-based positive temperature coefficient (PTC) temperature sensor in SOD70 plastic package, with nominal resistance of 1960–2000 Ω at 25 °C, ±1.27 K max temperature error at 25 °C, and 0.79 %/K temperature coefficient - used for precision thermal monitoring in motor windings, power supply thermal protection, and HVAC ambient sensing.

For engineers reviewing the KTY81/221,112 datasheet, KTY81/221,112 pinout, KTY81/221,112 application, or KTY81/221,112 equivalent, this page delivers verified specifications, SOD70 package dimensions, two-terminal linear resistance-temperature behavior, thermal time constant data (3 s in flowing liquid), and direct alternatives for industrial temperature sensing designs.

Technical Context

The KTY81/221,112 operates as a two-terminal passive resistive sensor requiring external bias current (recommended 1 mA continuous); its resistance increases predictably with temperature across −55 °C to +150 °C, exhibiting near-linear R–T behavior above 0 °C and fail-safe PTC response under overtemperature conditions.

It features long-term drift of ≤3.2 Ω after 10,000 h at 150 °C, thermal time constants of 3 s (flowing liquid), 5 s (still liquid), and 30 s (still air), and is rated for continuous operation up to 10 mA at 25 °C ambient - derating to 2 mA at 150 °C per absolute maximum ratings.

Key Specifications

Parameter	Value and Actual Design Meaning
R₂₅	1960–2000 Ω at 25 °C (defines baseline calibration point for analog front-end scaling)
TC	0.79 %/K (enables stable linearized output over 0–100 °C range with <±2 K error)
R₁₀₀/R₂₅	1.676–1.716 (confirms predictable resistance ratio for 100 °C reference point)
τ_th (flowing liquid)	3 s (supports fast thermal response in liquid-cooled systems like power converters)
Isen(cont) max	10 mA at 25 °C (sets upper limit for excitation current to avoid self-heating errors)
Tamb range	−55 °C to +150 °C (validates use in automotive engine bays and industrial motor enclosures)
ΔR₂₅ drift	≤3.2 Ω after 10,000 h @ 150 °C (ensures long-term calibration stability in high-temp applications)

Pinout & Package

The KTY81/221,112 is housed in the SOD70 plastic near-cylindrical single-ended package with two in-line leads, measuring 4.4–4.8 mm width × 5.0–5.2 mm height × 3.6–4.2 mm thickness, lead-to-lead distance 2.54 mm (bulk) or 5.08 mm (reel).

Pin/Terminal	Circuit Role	Design Meaning
1	Electrical contact	Unpolarized terminal - connects to bias current source or voltage divider node
2	Electrical contact	Unpolarized terminal - completes resistive path; interchangeable with Pin 1

Key Features

Feature	Design Value
Positive temperature coefficient (PTC)	Fail-safe behavior: resistance rises with temperature, preventing runaway in overtemp events
Virtually linear R–T curve	±1.27 K max error at 25 °C enables simple 2-point calibration without complex polynomial compensation
Long-term stability	≤3.2 Ω resistance drift after 10,000 h at 150 °C supports 10+ year field reliability in industrial gear
ESD-sensitive handling	Requires ESD-safe transport and PCB assembly to prevent latent damage to silicon junction

Applications

Motor Winding Protection	Power Supply Thermal Monitoring
Use Scenario: Embedded inside stator windings of AC induction motors to detect overheating during overload or cooling failure. IC Role / Device Role / Timing Role: Passive resistive sensor providing analog R–T feedback to microcontroller ADC or dedicated thermal comparator. Use Value: 0.79 %/K TC and 3.2 Ω long-term drift enable accurate trip-point detection at 130 °C with <±3 K margin over 10-year life.	Use Scenario: Mounted on heatsinks or MOSFET drain pads in DC–DC converters to monitor thermal headroom. IC Role / Device Role / Timing Role: Two-terminal analog temperature transducer interfaced via constant-current source and precision resistor divider. Use Value: 3 s thermal time constant in forced-air flow allows real-time thermal throttling response before critical junction temperatures are exceeded.
HVAC Ambient Sensing	Industrial Oven Temperature Control
Use Scenario: Installed in air ducts or thermostat housings to measure ambient cabin or room temperature. IC Role / Device Role / Timing Role: Calibration-grade PTC element referenced against known voltage sources for analog temperature readout. Use Value: R₁₀₀/R₂₅ = 1.676–1.716 ensures repeatable 100 °C reference matching across production batches for HVAC setpoint accuracy.	Use Scenario: Embedded in oven chamber walls or heating element mounts for closed-loop PID temperature regulation. IC Role / Device Role / Timing Role: High-stability resistive sensor operating continuously at 125–150 °C ambient in industrial bake cycles. Use Value: ≤3.2 Ω resistance drift after 10,000 h at 150 °C maintains ±0.5 °C control accuracy over multi-year oven service life.

Motor Winding Protection

Power Supply Thermal Monitoring

Use Scenario: Embedded inside stator windings of AC induction motors to detect overheating during overload or cooling failure.

IC Role / Device Role / Timing Role: Passive resistive sensor providing analog R–T feedback to microcontroller ADC or dedicated thermal comparator.

Use Value: 0.79 %/K TC and 3.2 Ω long-term drift enable accurate trip-point detection at 130 °C with <±3 K margin over 10-year life.

Use Scenario: Mounted on heatsinks or MOSFET drain pads in DC–DC converters to monitor thermal headroom.

IC Role / Device Role / Timing Role: Two-terminal analog temperature transducer interfaced via constant-current source and precision resistor divider.

Use Value: 3 s thermal time constant in forced-air flow allows real-time thermal throttling response before critical junction temperatures are exceeded.

HVAC Ambient Sensing

Industrial Oven Temperature Control

Use Scenario: Installed in air ducts or thermostat housings to measure ambient cabin or room temperature.

IC Role / Device Role / Timing Role: Calibration-grade PTC element referenced against known voltage sources for analog temperature readout.

Use Value: R₁₀₀/R₂₅ = 1.676–1.716 ensures repeatable 100 °C reference matching across production batches for HVAC setpoint accuracy.

Use Scenario: Embedded in oven chamber walls or heating element mounts for closed-loop PID temperature regulation.

IC Role / Device Role / Timing Role: High-stability resistive sensor operating continuously at 125–150 °C ambient in industrial bake cycles.

Use Value: ≤3.2 Ω resistance drift after 10,000 h at 150 °C maintains ±0.5 °C control accuracy over multi-year oven service life.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TSI302-221	Same R₂₅ range (1960–2000 Ω), but TO-92 package; 0.82 %/K TC vs. 0.79 %/K	TO-92 offers better mechanical rigidity in vibration-prone environments; slightly higher TC improves sensitivity at mid-range temps	Select when board space permits larger through-hole footprint and higher TC sensitivity is preferred
KTY81/220	Identical SOD70 package and pinout; R₂₅ = 1960–2040 Ω (wider tolerance), TC = 0.79 %/K	Looser R₂₅ tolerance increases initial calibration effort; otherwise identical thermal performance and drift	Select only if cost reduction outweighs need for tighter 1960–2000 Ω binning at 25 °C

Compared with TSI302-221 and KTY81/220, the KTY81/221,112 provides tighter R₂₅ tolerance (1960–2000 Ω) in the compact SOD70 surface-mount package, enabling higher placement density and lower assembly cost while maintaining identical long-term drift and thermal response specs.

Availability

KTY81/221,112 is available at Aetrix Electronics and suitable for motor winding protection, power supply thermal monitoring, and HVAC ambient sensing requiring stable component supply across extended industrial temperature ranges.

Supply support for KTY81/221,112 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 markets.

The KTY81 series belongs to NXP's analog sensor product line, designed specifically for high-reliability, low-drift temperature measurement in harsh thermal environments where silicon PTC characteristics provide inherent safety and stability.

FAQ

What is the nominal resistance of KTY81/221,112 at 25 °C?

The KTY81/221,112 has a specified resistance range of 1960 Ω to 2000 Ω at 25 °C under 1 mA continuous excitation current. This tight tolerance bin enables precise system-level calibration without individual unit trimming, and is confirmed in Table 1 and Table 11 of the NXP KTY81_SER_5 datasheet.

Does KTY81/221,112 require polarity-aware connection?

No - the KTY81/221,112 is a two-terminal passive resistor with no polarity; Pins 1 and 2 are electrically identical and interchangeable. Its SOD70 package contains no internal diodes or active circuitry, so orientation during placement does not affect function, as stated in Table 2 (Pinning) of the official datasheet.

What is the maximum continuous operating current for KTY81/221,112?

The KTY81/221,112 supports up to 10 mA continuous sensor current at 25 °C ambient, derating to 2 mA at 150 °C, per Table 5 (Limiting Values) in the NXP datasheet. Exceeding these values risks self-heating errors and accelerated long-term drift beyond the rated 3.2 Ω after 10,000 h.

How does the thermal time constant of KTY81/221,112 vary with medium?

The KTY81/221,112 exhibits a thermal time constant of 3 seconds in flowing liquid, 5 seconds in still liquid, and 30 seconds in still air (Table 6), directly impacting response speed in different thermal environments - e.g., fast reaction in liquid-cooled inverters versus slower tracking in ambient air-sensing applications.

Is KTY81/221,112 suitable for automotive under-hood applications?

Yes - the KTY81/221,112 is rated for −55 °C to +150 °C ambient operation (Table 5) and demonstrates ≤3.2 Ω resistance drift after 10,000 h at 150 °C (Table 6), meeting key requirements for engine bay thermal sensors. Its SOD70 package also complies with JEDEC moisture sensitivity level (MSL) standards for reflow compatibility.

KTY81/221,112 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:: 1.98 kOhms

Resistance Tolerance:: -

Operating Temperature:: -55°C ~ 150°C

Power - Max:: -

Mounting Type:: Through Hole

Grade:: -

Qualification:: -

Supplier Device Package:: PBCYT2

KTY81/221,112 FAQ

1.How can I place an order for KTY81/221,112 through Aetrix?

Please submit a Request for Quotation (RFQ) for KTY81/221,112 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 KTY81/221,112 reliable?

The price and inventory of KTY81/221,112 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KTY81/221,112 is usually 5 days.

3.What payment methods are accepted for KTY81/221,112?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KTY81/221,112 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KTY81/221,112?

KTY81/221,112 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KTY81/221,112 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 KTY81/221,112?

For technical support, including KTY81/221,112 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KTY81/221,112 requirements.

6.How does Aetrix verify that KTY81/221,112 is sourced from the original manufacturer or authorized distributors?

All KTY81/221,112 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 KTY81/221,112 meets industry standards.

7.What is the process for return or replacement of KTY81/221,112?

All KTY81/221,112 units undergo pre-shipment inspection (PSI). If there is an issue with KTY81/221,112, 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 KTY81/221,112 part is unused and in its original packaging.

Return procedure for KTY81/221,112:

1.Submit a request within 90 days.

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

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