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onsemi KSD985OSTU
- Part No.:
- KSD985OSTU
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-225AA, TO-126-3
- Datasheet:
-
KSD985OSTU.pdf
- Description:
- TRANS NPN DARL 60V 1.5A TO-126-3
- Quantity:
- Payment:
- Shipping:
Inventory:9,029
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Product details
Overview
KSD985OSTU from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon Darlington transistor optimized for low-frequency power amplification and industrial low-speed switching. It delivers hFE2 of 2000–5000 (R-class), VCEO = 60 V, IC = 1.5 A DC / 3.0 A pulse, VCE(sat) = 1.5 V at IC = 1 A/IB = 1 mA, and operates up to TJ = 150°C - used in relay drivers and motor control stages.
For engineers reviewing the KSD985OSTU datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-126 package thermal performance (PC = 10 W at TC = 25°C), Darlington gain structure, saturation voltage trade-off versus base drive current, and safe operating area limitations under pulsed conditions.
Technical Context
The KSD985OSTU implements a two-stage monolithic Darlington configuration with integrated emitter-base resistor network enabling high DC current gain (hFE2 ≥ 2000 at IC = 1 A) while maintaining stable cutoff behavior (ICER ≤ 1.0 mA at TC = 125°C with RBE = 51 Ω). Its VCEO rating of 60 V and VCBO of 150 V define breakdown margins for inductive load switching.
Thermal design relies on case-mounted heatsinking: PC derates linearly from 10 W at TC = 25°C to zero at TC = 175°C, and SOA curves specify maximum simultaneous VCE/IC limits under DC, pulsed (300 µs/10%), and reverse-bias conditions - critical for snubberless relay coil driving.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 60 V - maximum collector-emitter voltage before breakdown in common-emitter configuration; defines safe operating headroom for 48 V industrial control rails. |
| hFE2 | 2000–5000 - DC current gain at IC = 1 A, VCE = 2 V; enables low-base-drive switching of 1 A loads with ~500 µA IB. |
| VCE(sat) | 1.5 V @ IC = 1 A, IB = 1 mA - saturation voltage determines conduction loss and junction temperature rise under continuous load. |
| PC (TC=25°C) | 10 W - maximum power dissipation with case held at 25°C; requires heatsink for >1 W continuous operation. |
| tON / tF | 0.5 µs / 1.0 µs - turn-on and fall times at VCC = 50 V, RL = 50 Ω; suitable for ≤100 kHz switching, not RF or fast digital use. |
| JEDEC TO-126 | 3-pin through-hole package with emitter-collector-base pinout (1-E, 2-C, 3-B); standardized mechanical footprint and thermal pad mounting. |
Pinout & Package
Package: JEDEC TO-126, epoxy-molded, single-ended heat slug (pin 2 connected to collector and case). Mounting requires mechanical fixation and thermal interface to heatsink.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Emitter | Low-impedance output node; connects to load return or ground; carries full load current and contributes to thermal path via leadframe. |
| 2 | Collector | High-current input node tied to VCC rail or inductive load; electrically and thermally connected to metal tab for heatsinking. |
| 3 | Base | Control input requiring current-driven bias (not voltage-driven); 1 mA IB needed for 1 A IC saturation; sensitive to ESD. |
Key Features
| Feature | Design Value |
|---|---|
| High Darlington hFE | hFE2 = 2000–5000 minimizes required base drive current, reducing driver stage complexity and power loss in discrete logic-level interfaces. |
| Robust SOA | DC and pulsed Safe Operating Area validated per Figure 6; supports inductive load switching without external snubbers up to specified VCE/IC limits. |
| Thermally rated package | TO-126 metal tab enables direct heatsink mounting; 10 W PC at TC = 25°C allows compact thermal design in space-constrained industrial enclosures. |
| Industrial temperature range | Specified operation from –55°C to +150°C junction temperature; qualified for extended life in motor drives, PLC outputs, and HVAC controls. |
Applications
| Relay Driver Stage | DC Motor On/Off Control |
|---|---|
Use Scenario: Driving 12–48 V DC electromagnetic relays with coil currents up to 1.2 A in programmable logic controller (PLC) output modules. IC Role / Device Role / Timing Role: High-gain Darlington switch providing galvanically isolated load switching via optocoupler-coupled base drive. Use Value: Eliminates need for pre-driver transistors; 1 mA base current suffices for full relay actuation, simplifying PCB layout and reducing component count. | Use Scenario: Controlling bidirectional brushed DC motors (≤30 W) in industrial actuators using H-bridge half-bridge configurations. IC Role / Device Role / Timing Role: Low-speed power switch in one leg of discrete H-bridge; handles stall current surges up to 3 A pulse. Use Value: VCE(sat) = 1.5 V limits conduction loss to <1.5 W at 1 A, enabling passive heatsinking instead of forced-air cooling. |
| Solenoid Actuator Interface | Heater Power Stage |
Use Scenario: Switching 24 V solenoid valves (0.8–1.5 A hold current) in factory automation fluid control systems. IC Role / Device Role / Timing Role: Final-stage current amplifier interfacing microcontroller GPIO to high-inductance load; absorbs back-EMF via built-in SOA margin. Use Value: ICER ≤ 1.0 mA at 125°C ensures reliable turn-off even in hot control cabinets, preventing unintended valve creep. | Use Scenario: Regulating resistive heating elements (e.g., cartridge heaters) in temperature-controlled ovens and molding equipment. IC Role / Device Role / Timing Role: Phase-angle or burst-fire switched power stage controlled by zero-crossing TRIAC driver circuitry. Use Value: 60 V VCEO provides 2× margin over 24 V heater supply, accommodating line transients and ensuring long-term reliability in harsh EMI environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Darlington transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MJD122G | VCEO = 100 V, hFE = 1000–4000, TO-220 package, higher thermal mass but larger footprint. | Better suited for higher-voltage (≤80 V) inductive loads; requires different heatsink interface and PCB layout. | Select when higher VCEO margin or improved thermal inertia is required; not drop-in due to TO-220 vs. TO-126 mechanical mismatch. |
| BD679A | VCEO = 80 V, hFE = 750–4000, TO-126 package, lower gain consistency and wider hFE spread (750–4000). | Acceptable where tighter hFE binning is unnecessary and 80 V rating suffices; less predictable base drive requirements. | Choose for cost-sensitive designs accepting wider hFE variation; same footprint enables direct board replacement if SOA and gain meet system needs. |
Compared with MJD122G and BD679A, the KSD985OSTU offers tighter hFE binning (R-class 2000–5000), optimized 60 V rating for 48 V systems, and proven SOA for relay/solenoid drive - making it preferable where predictable low-base-drive switching and compact TO-126 mounting are prioritized.
Availability
KSD985OSTU is available at Aetrix Electronics and suitable for relay driver stages, DC motor on/off control, solenoid actuator interfaces, and heater power stages requiring stable component supply across industrial OEM production cycles.
Supply support for KSD985OSTU 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
ON Semiconductor (formerly Fairchild Semiconductor) is a global semiconductor supplier focused on energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud power markets.
The KSD985OSTU belongs to Fairchild's legacy discrete bipolar transistor product line, designed specifically for robust, low-frequency power switching in industrial control hardware where reliability, thermal stability, and high DC gain are essential.
FAQ
What is the maximum continuous collector current for the KSD985OSTU?
The KSD985OSTU supports a maximum continuous collector current (IC) of 1.5 A at Ta = 25°C. Derating applies above ambient temperature; actual usable current depends on heatsinking and case temperature. At TC = 25°C, the device can dissipate up to 10 W, allowing sustained 1.5 A operation only with adequate thermal management. Always verify junction temperature using the thermal resistance data and SOA curves in the official KSD985OSTU datasheet.
Is the KSD985OSTU pin-compatible with the KSD986OSTU?
No, the KSD985OSTU and KSD986OSTU are not functionally interchangeable despite identical TO-126 packaging and pinout. The KSD986OSTU has a higher VCEO rating (80 V vs. 60 V) and different hFE classification bands. Substituting KSD985OSTU for KSD986OSTU in 80 V circuits risks premature breakdown; always match the exact voltage rating required by the application when selecting between these variants.
Does the KSD985OSTU require a base resistor, and what value is recommended?
Yes, the KSD985OSTU requires an external base resistor to limit IB and ensure stable saturation. For IC = 1 A, typical design uses IB ≈ 1 mA (per datasheet test condition), so with a 5 V logic drive and VBE(sat) ≈ 2.0 V, a 3.0 kΩ resistor is appropriate. Lower values improve saturation margin but increase driver loading; always verify actual IB and VCE(sat) under operating conditions, as hFE varies with temperature and current.
Can the KSD985OSTU be used in PWM motor speed control applications?
The KSD985OSTU is not recommended for PWM-based speed control due to its relatively slow switching (tON = 0.5 µs, tF = 1.0 µs) and lack of specified switching loss characteristics. It is engineered for low-speed on/off switching (e.g., relay, solenoid, heater control) up to ~100 kHz. For PWM motor control, MOSFETs or faster BJTs with defined gate/base charge and switching energy specs are preferred to minimize heat generation and ensure waveform fidelity.
What is the meaning of the 'R' suffix in KSD985OSTU's hFE classification?
The 'R' in KSD985OSTU denotes its hFE2 bin: 2000–5000 at IC = 1 A and VCE = 2 V. This classification ensures consistent current gain across units, simplifying base drive design in production systems. Other bins include 'O' (4000–10000) and 'Y' (8000–30000); the R-bin balances gain stability, saturation voltage, and thermal performance for general-purpose industrial switching - a key specification verified per unit during KSD985OSTU manufacturing test.
KSD985OSTU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-225AA, TO-126-3
- Packaging:
- Tube
- Product Status:
- Obsolete
- Transistor Type:
- NPN - Darlington
- Current - Collector (Ic) (Max):
- 1.5 A
- Voltage - Collector Emitter Breakdown (Max):
- 60 V
- Vce Saturation (Max) @ Ib, Ic:
- 1.5V @ 1mA, 1A
- Current - Collector Cutoff (Max):
- 10µA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 4000 @ 1A, 2V
- Power - Max:
- 1 W
- Frequency - Transition:
- -
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-126-3
KSD985OSTU FAQ
1.How can I place an order for KSD985OSTU through Aetrix?
Please submit a Request for Quotation (RFQ) for KSD985OSTU 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 KSD985OSTU reliable?
The price and inventory of KSD985OSTU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KSD985OSTU is usually 5 days.
3.What payment methods are accepted for KSD985OSTU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KSD985OSTU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for KSD985OSTU?
KSD985OSTU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your KSD985OSTU 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 KSD985OSTU?
For technical support, including KSD985OSTU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KSD985OSTU requirements.
6.How does Aetrix verify that KSD985OSTU is sourced from the original manufacturer or authorized distributors?
All KSD985OSTU 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 KSD985OSTU meets industry standards.
7.What is the process for return or replacement of KSD985OSTU?
All KSD985OSTU units undergo pre-shipment inspection (PSI). If there is an issue with KSD985OSTU, 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 KSD985OSTU part is unused and in its original packaging.
Return procedure for KSD985OSTU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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