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

Infineon Technologies KTY21-7

Name: KTY21-7
Brand: Infineon Technologies
SKU: KTY21-7
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: KTY21-7

Manufacturer:: Infineon Technologies

Category:: PTC Thermistors

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

Datasheet:: KTY21-7.pdf

Description:: SENSOR PTC 1.015KOHM 3% TO92MINI

Quantity:: RFQ Add To RFQ list

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Inventory:113,400

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Product details

Overview

KTY21-7 from Infineon Technologies is a silicon-based positive temperature coefficient (PTC) temperature sensor in TO-92 Mini package, with nominal resistance R25 = 1005 Ω (min 1005 Ω, max 1025 Ω at 25 °C), operating range −50 °C to +150 °C, thermal time constant τ_air = 11 s (typ.), and polarity-independent symmetrical construction. It serves as an analog temperature sensing element in motor winding protection circuits.

For engineers reviewing the KTY21-7 datasheet, KTY21-7 pinout, KTY21-7 application, or KTY21-7 equivalent, this device is selected for precision linearized resistance-vs-temperature response in industrial motor control, HVAC blower monitoring, and power supply thermal regulation where ±1% R25 tolerance and long-term stability are required.

Technical Context

The KTY21-7 uses an n-conducting silicon crystal in planar technology, with resistance defined by a second-order polynomial: R_T = R₂₅ × [1 + α·ΔT + β·(ΔT)²], where α = 7.88×10⁻³ K⁻¹ and β = 1.937×10⁻⁵ K⁻². Its output is inherently linearized over −30 °C to +130 °C via this curvature.

It operates at 1 mA bias current, exhibits polarity independence due to symmetrical two-terminal construction, and delivers stable resistance values with <0.1%/year long-term drift. No external signal conditioning is required beyond simple voltage divider readout.

Key Specifications

Parameter	Value and Actual Design Meaning
R₂₅ (nominal)	1005 Ω - defines baseline resistance at 25 °C for voltage-divider scaling
R₂₅ tolerance	±1% - enables direct calibration without individual trimming in production
Temp range	−50 °C to +150 °C - supports motor winding hot-spot monitoring up to Class H insulation limits
τ_air	11 s (typ.) - ensures responsive thermal tracking in forced-air-cooled systems
Max operating current	7 mA - limits self-heating error to <0.5 °C at 1 mA bias
Temp coefficient shape	Second-order parabolic (α, β known) - allows accurate digital compensation using fixed-point math

Pinout & Package

Two-terminal device in TO-92 Mini plastic package (3.3 mm × 1.7 mm × 4.0 mm), leaded, axial through-hole mounting. Pin 1 and Pin 2 are electrically identical; no polarity assignment required.

Pin/Terminal	Circuit Role	Design Meaning
Terminal 1	Anode / Cathode (symmetrical)	Interchangeable connection point; no DC polarity sensitivity
Terminal 2	Anode / Cathode (symmetrical)	Interchangeable connection point; enables bidirectional biasing

Key Features

Feature	Design Value
Positive temperature coefficient	Monotonic, predictable R-T rise prevents false trip in overtemp shutdown logic
Linearized output curve	Second-order polynomial coefficients published - enables firmware-based temperature calculation without lookup tables
Fast thermal response	11 s air time constant - suitable for real-time motor thermal modeling in closed-loop control
±1% R₂₅ tolerance	Reduces need for per-unit calibration in high-volume motor driver BOMs

Applications

Motor Winding Protection

HVAC Blower Monitoring

Use Scenario: Embedded inside stator windings of industrial 3-phase motors to detect thermal overload before insulation failure.

IC Role / Device Role / Timing Role: Analog temperature transducer providing resistance-proportional feedback to comparator or ADC input.

Use Value: Enables Class H thermal margin compliance (180 °C winding limit) with 1005 Ω baseline enabling precise 100 °C trip point setting.

Use Scenario: Mounted on HVAC blower motor housing to monitor bearing and coil temperature during continuous duty cycles.

IC Role / Device Role / Timing Role: Passive PTC sensor in voltage divider, interfaced to microcontroller ADC with 12-bit resolution.

Use Value: 11 s τ_air matches blower thermal dynamics, avoiding nuisance trips during transient load changes.

Power Supply Thermal Regulation

Industrial Pump Controller

Use Scenario: Integrated into switch-mode power supply heatsink to regulate fan speed and throttle output under sustained load.

IC Role / Device Role / Timing Role: Temperature-sensing element in analog feedback loop controlling PWM fan driver.

Use Value: ±1% R₂₅ tolerance ensures consistent thermal setpoints across production batches without recalibration.

Use Scenario: Installed in submersible pump motor housing to prevent dry-run damage and seal overheating.

IC Role / Device Role / Timing Role: Two-terminal analog sensor directly connected to protection relay input circuit.

Use Value: Polarity independence simplifies PCB layout and field wiring in harsh, vibration-prone environments.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
KTY21-6	R₂₅ = 990 Ω (min/max 990–1010 Ω); 15 °C lower trip point at same divider ratio	Suitable where tighter low-end thermal margin is needed below 80 °C	Select when system requires earlier thermal intervention at moderate temperatures
KTY23-7	SOT-23 surface-mount package; identical R₂₅ (1005 Ω) but τ_air = 7 s (faster response)	Better suited for compact, high-density PCBs with airflow constraints	Choose for space-constrained designs requiring faster thermal tracking

Compared with KTY21-6 and KTY23-7, the KTY21-7 offers optimal balance of mid-range resistance accuracy, TO-92 Mini mechanical robustness, and 11 s air response-ideal for retrofit and service replacement in legacy motor protection modules.

Availability

KTY21-7 is available at Aetrix Electronics and suitable for motor winding protection, HVAC blower monitoring, and power supply thermal regulation requiring stable component supply across extended production lifecycles.

Supply support for KTY21-7 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, sensor, and automotive ICs, with global manufacturing and quality certification to IATF 16949 and ISO 9001.

The KTY-series is Infineon's dedicated line of silicon PTC temperature sensors designed specifically for high-reliability thermal monitoring in rotating machinery, power electronics, and industrial control systems.

FAQ

What is the maximum recommended bias current for KTY21-7?

The absolute maximum operating current is 7 mA, but the recommended operating current is 1 mA. At 1 mA, self-heating remains below 0.5 °C, preserving measurement accuracy. Higher currents increase thermal error and accelerate long-term drift, especially above 5 mA.

Can KTY21-7 be used in a Wheatstone bridge configuration?

Yes - its symmetrical two-terminal construction and tight R₂₅ tolerance make it suitable as one arm of a Wheatstone bridge. Paired with a matched fixed resistor, it provides differential output for improved noise immunity and offset rejection in noisy industrial environments.

Does KTY21-7 require polarity-aware PCB layout?

No - the device has symmetrical construction with no anode/cathode distinction. Terminals are electrically interchangeable, eliminating orientation constraints during manual assembly or automated placement, and simplifying field wiring in maintenance scenarios.

How is temperature calculated from KTY21-7 resistance?

Temperature is derived using the published second-order equation: T = [−α + √(α² − 4β × (1 − R_T/R₂₅))]/(2β), where α = 7.88×10⁻³ K⁻¹ and β = 1.937×10⁻⁵ K⁻². This formula is valid from −30 °C to +130 °C and requires only R_T measurement and R₂₅ = 1005 Ω.

KTY21-7 Specifications

Product attributes: Attribute value

Manufacturer:: Infineon Technologies

Series:: -

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

Packaging:: Bulk

Product Status:: Active

Resistance @ 25°C:: 1.015 kOhms

Resistance Tolerance:: ±3%

Operating Temperature:: -50°C ~ 150°C

Power - Max:: -

Mounting Type:: Through Hole

Grade:: -

Qualification:: -

Supplier Device Package:: TO-92MINI

KTY21-7 FAQ

1.How can I place an order for KTY21-7 through Aetrix?

Please submit a Request for Quotation (RFQ) for KTY21-7 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 KTY21-7 reliable?

The price and inventory of KTY21-7 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KTY21-7 is usually 5 days.

3.What payment methods are accepted for KTY21-7?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KTY21-7 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for KTY21-7?

KTY21-7 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your KTY21-7 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 KTY21-7?

For technical support, including KTY21-7 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KTY21-7 requirements.

6.How does Aetrix verify that KTY21-7 is sourced from the original manufacturer or authorized distributors?

All KTY21-7 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 KTY21-7 meets industry standards.

7.What is the process for return or replacement of KTY21-7?

All KTY21-7 units undergo pre-shipment inspection (PSI). If there is an issue with KTY21-7, 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 KTY21-7 part is unused and in its original packaging.

Return procedure for KTY21-7:

1.Submit a request within 90 days.

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

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