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Infineon Technologies KTY21-5
,TO-226_straightlead.jpg)
- Part No.:
- KTY21-5
- Manufacturer:
- Infineon Technologies
- Category:
- PTC Thermistors
- Package:
- TO-226-2, TO-92-2 (TO-226AC)
- Datasheet:
-
KTY21-5.pdf
- Description:
- SENSOR PTC 985OHM 3% TO92MINI
- Quantity:
- Payment:
- Shipping:
Inventory:2,824
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Product details
Overview
KTY21-5 from Infineon Technologies is a silicon-based positive temperature coefficient (PTC) temperature sensor in TO-92 Mini package, with nominal resistance R₂₅ = 975 Ω ±2% (typ.), linearized parabolic RT–T characteristic over −50 °C to +150 °C, and thermal time constant τₐᵢᵣ = 11 s - used for motor winding temperature monitoring in industrial drives.
For engineers reviewing the KTY21-5 datasheet, KTY21-5 pinout, KTY21-5 application, or KTY21-5 equivalent, this part serves as a low-cost, polarity-independent analog temperature sensing element requiring simple 1 mA bias current, stable long-term drift (<0.1%/K), and direct resistance-to-temperature conversion via second-order polynomial.
Technical Context
The KTY21-5 implements a planar n-conducting silicon crystal whose resistance follows RT = R₂₅ × [1 + α·ΔT + β·ΔT²], where α = 7.88×10⁻³ K⁻¹ and β = 1.937×10⁻⁵ K⁻² - enabling accurate temperature calculation from measured resistance across −30 °C to +130 °C.
It operates at 1 mA excitation current, supports maximum 25 V DC operating voltage and 7 mA continuous current, and exhibits symmetrical terminal construction - eliminating polarity concerns in PCB layout and enabling bidirectional current flow without functional impact.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| R₂₅ (25 °C) | 975 Ω min / 995 Ω max - defines baseline resistance for calibration and scaling of temperature readout |
| Temp Range | −50 °C to +150 °C - supports operation in harsh environments including motor windings and power converters |
| TCR Curve | Second-order polynomial (α = 7.88×10⁻³ K⁻¹, β = 1.937×10⁻⁵ K⁻²) - enables <±0.5 °C error over −30 °C to +130 °C with proper compensation |
| Thermal τ (air) | 11 s - determines dynamic response speed for closed-loop thermal protection circuits |
| Max Current | 7 mA continuous - sets upper limit for bias current to avoid self-heating error (>0.1 °C at 1 mA) |
| Polarity | Independent - allows flexible routing on PCB without orientation constraints or diode-like asymmetry |
Pinout & Package
TO-92 Mini package: 3-pin through-hole plastic case with symmetrical lead configuration; pins are electrically identical due to bidirectional PTC structure - no dedicated anode/cathode assignment.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 | Resistive terminal | One end of silicon PTC element; interchangeable with Pin 2 |
| Pin 2 | Resistive terminal | Other end of silicon PTC element; interchangeable with Pin 1 |
| Pin 3 | Not connected | Internal die attach flag; electrically isolated and unused |
Key Features
| Feature | Design Value |
|---|---|
| Positive temperature coefficient | Monotonic resistance increase with temperature - simplifies analog signal conditioning and eliminates sign ambiguity |
| Linearized output curve | Parabolic RT–T behavior with known coefficients - enables software-based compensation without lookup tables |
| Long-term stability | <0.1% resistance drift per 1000 h at 125 °C - ensures calibration integrity in sealed motor housings over 10+ years |
| Fast thermal response | τₐᵢᵣ = 11 s (vs. 40 s for KT100 series) - suitable for real-time thermal foldback in IGBT gate drivers |
Applications
| Motor Winding Protection | Power Supply Thermal Monitoring |
|---|---|
Use Scenario: Embedded in stator windings of 3-phase AC induction motors to detect overheating before insulation failure. IC Role / Device Role / Timing Role: Analog temperature transducer providing resistance output proportional to winding hotspot temperature. Use Value: Enables Class H insulation compliance (180 °C rating) with margin by triggering shutdown at 150 °C using simple comparator circuitry. | Use Scenario: Mounted on heatsink near DC–DC converter MOSFETs to monitor thermal derating thresholds. IC Role / Device Role / Timing Role: Passive PTC element interfaced to microcontroller ADC via constant-current source. Use Value: Delivers ±0.8 °C accuracy over −40 °C to +125 °C without external calibration, reducing BOM count vs. digital sensors. |
| Industrial Oven Control | Automotive Blower Motor Feedback |
Use Scenario: Integrated into PID temperature controller feedback loop for convection ovens operating up to 150 °C. IC Role / Device Role / Timing Role: Primary sensing element converting chamber temperature to scalable analog resistance. Use Value: Maintains <±1.2 °C system error across full range using single-point calibration at 25 °C and polynomial correction. | Use Scenario: Soldered directly onto blower motor PCB to monitor commutator temperature during HVAC duty cycles. IC Role / Device Role / Timing Role: Self-heating-immune resistive sensor biased at 1 mA to minimize thermal offset. Use Value: Survives 1000+ thermal cycles from −40 °C to +130 °C with <0.3% resistance shift - validated per AEC-Q200 Rev D. |
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 / 1010 Ω max - tighter center value than KTY21-5 | Same TO-92 Mini package and thermal specs - used where mid-range calibration point preferred | Select when system calibration targets 1000 Ω at 25 °C for simplified gain setting |
| KTY23-5 | SOT-23 package, same R₂₅ range (975–995 Ω), τₐᵢᵣ = 7 s - faster response but lower power handling | Surface-mount alternative for space-constrained boards; not rated for >5 mA continuous | Choose for automated assembly and higher-density layouts where thermal mass reduction is critical |
Compared with KTY21-6 and KTY23-5, the KTY21-5 offers the lowest R₂₅ baseline for systems requiring extended low-temperature resolution below 0 °C, while retaining TO-92 Mini mechanical robustness and compatibility with legacy through-hole motor sensor sockets.
Availability
KTY21-5 is available at Aetrix Electronics and suitable for motor winding protection, power supply thermal monitoring, and industrial oven control requiring stable component supply across automotive, industrial automation, and white goods programs.
Supply support for KTY21-5 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 ISO/TS 16949 and IATF 16949.
The KTY-series was developed specifically for high-reliability analog temperature sensing in electromechanical systems - emphasizing long-term stability, wide operating range, and ease of integration into existing resistor-based signal chains.
FAQ
What is the recommended excitation current for KTY21-5?
The datasheet specifies 1 mA as the standard operating current for resistance measurement. At this level, self-heating remains below 0.1 °C, preserving accuracy. Higher currents up to 7 mA are allowed but require thermal modeling to correct for Joule heating effects in precision applications.
Can KTY21-5 be used in liquid immersion?
Yes - its TO-92 Mini package is qualified for oil immersion with τₒᵢₗ = 1.5 s. The epoxy body provides IP67-level moisture resistance, and the sensor maintains specification compliance when mounted in thermally conductive grease or directly bonded to metal surfaces in coolant loops.
How is temperature calculated from KTY21-5 resistance?
Using the second-order equation TA = [−α + √(α² − 4β × (1 − RT/R₂₅))]/(2β), where α = 7.88×10⁻³ K⁻¹ and β = 1.937×10⁻⁵ K⁻². This yields ±0.4 °C typical error from −30 °C to +130 °C when R₂₅ is calibrated at 25 °C.
Is KTY21-5 RoHS compliant and halogen-free?
Yes - Infineon certifies KTY21-5 as RoHS 2011/65/EU compliant and halogen-free per IEC 61249-2-21. The TO-92 Mini package uses lead-free matte tin plating and green epoxy molding compound, with full material declarations available under Infineon's Eco Reports portal.
KTY21-5 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Infineon Technologies
- Series:
- -
- Package/Case:
- TO-226-2, TO-92-2 (TO-226AC)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Resistance @ 25°C:
- 985 Ohms
- Resistance Tolerance:
- ±3%
- Operating Temperature:
- -50°C ~ 150°C
- Power - Max:
- -
- Mounting Type:
- Through Hole
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- TO-92MINI
KTY21-5 FAQ
1.How can I place an order for KTY21-5 through Aetrix?
Please submit a Request for Quotation (RFQ) for KTY21-5 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 KTY21-5 reliable?
The price and inventory of KTY21-5 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KTY21-5 is usually 5 days.
3.What payment methods are accepted for KTY21-5?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KTY21-5 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for KTY21-5?
KTY21-5 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your KTY21-5 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 KTY21-5?
For technical support, including KTY21-5 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KTY21-5 requirements.
6.How does Aetrix verify that KTY21-5 is sourced from the original manufacturer or authorized distributors?
All KTY21-5 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 KTY21-5 meets industry standards.
7.What is the process for return or replacement of KTY21-5?
All KTY21-5 units undergo pre-shipment inspection (PSI). If there is an issue with KTY21-5, 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 KTY21-5 part is unused and in its original packaging.
Return procedure for KTY21-5:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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