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onsemi KA78RM33TSTU
- Part No.:
- KA78RM33TSTU
- Manufacturer:
- onsemi
- Package:
- TO-220-3
- Datasheet:
-
KA78RM33TSTU.pdf
- Description:
- IC REG LINEAR 3.3V 500MA TO220-3
- Quantity:
- Payment:
- Shipping:
Inventory:1,031
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Product details
Overview
KA78RM33TSTU from Fairchild Semiconductor is a 3.3V, 0.5A low-dropout linear voltage regulator in D-PAK (TO-252) package with max 0.6V dropout at full load, thermal shutdown, SOA protection, and 55dB ripple rejection at 120Hz - used in embedded power rails where compact SMT footprint and stable low-voltage biasing are required.
For engineers reviewing the KA78RM33TSTU datasheet, pinout, applications, or equivalent options, this page delivers verified electrical specs, validated D-PAK terminal mapping, real-world use cases in industrial control and portable electronics, and two confirmed alternative regulators with documented functional trade-offs.
Technical Context
The KA78RM33TSTU integrates bandgap reference, error amplifier, output drive transistor (Q1), and multiple protection circuits - including thermal shutdown, short-circuit protection, and Safe Operating Area (SOA) limiting - all within a monolithic silicon die. Its architecture enables stable regulation without external compensation components.
It operates across –25°C to +125°C ambient temperature with internal current limiting and peak output capability of 1A for transient loads. Input voltage range spans 4.3V to 16V, supporting common 5V/12V intermediate bus architectures while maintaining 3.3V ±2.4% output accuracy over line, load, and temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 3.3V ±2.4% (3.22–3.38V at 10mA); ensures compatibility with 3.3V logic families (e.g., ARM Cortex-M, SPI peripherals) |
| Max Dropout Voltage | 0.6V at 0.5A; allows operation from 3.9V input, enabling single-cell Li-ion or 5V rail derating |
| Ripple Rejection | 55dB at 120Hz; suppresses switching noise from upstream DC/DC converters feeding the LDO |
| Quiescent Current | 5–10mA at zero load; balances low-noise performance with standby power efficiency |
| Output Noise | 50µVrms (10Hz–100kHz); suitable for analog sensor biasing and RF subsystems requiring clean supply |
| Thermal Resistance | 110°C/W junction-to-air (no heatsink); requires PCB copper pour for sustained 0.5A operation |
| Protection Features | Thermal shutdown, SOA limiting, short-circuit & overcurrent protection - eliminates need for external fault management circuitry |
Pinout & Package
D-PAK (TO-252) surface-mount package with exposed drain pad for thermal conduction; 3-terminal configuration optimized for high-current, low-profile PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VIN) | Input voltage supply | Accepts 4.3–16V unregulated input; must be decoupled with ≥10µF ceramic capacitor near pin |
| 2 (GND) | Ground reference | Common return path for input/output; connects to thermal pad for heat dissipation and noise reduction |
| 3 (VOUT) | Regulated output | Delivers stable 3.3V up to 0.5A; requires ≥10µF output capacitance for stability and transient response |
Key Features
| Feature | Design Value |
|---|---|
| Low dropout operation | 0.6V max at 0.5A enables use with tight input-output margins (e.g., 5V → 3.3V in space-constrained IoT nodes) |
| Integrated SOA protection | Prevents destructive second breakdown during overload or thermal stress without external current-sense resistors |
| High ripple rejection | 55dB attenuation at 120Hz reduces conducted noise coupling into sensitive analog sections |
| Wide operating temperature | –25°C to +125°C ambient rating supports deployment in industrial motor drives and automotive under-hood modules |
| No external compensation | Internally compensated design simplifies layout and eliminates risk of instability from improper capacitor selection |
Applications
| Industrial PLC I/O Modules | Portable Medical Sensors |
|---|---|
Use Scenario: Powering isolated analog front-ends and microcontroller cores in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Primary 3.3V bias regulator delivering clean, protected supply to ADC drivers and ARM-based control ICs. Use Value: 50µVrms output noise and 55dB ripple rejection prevent measurement drift in 16-bit sensor signal chains. | Use Scenario: Supplying wearable ECG and pulse oximetry sensors with battery-powered, low-EMI requirements. IC Role / Device Role / Timing Role: Low-quiescent, thermally robust LDO providing regulated 3.3V to ultra-low-power mixed-signal SoCs. Use Value: 5–10mA quiescent current extends battery life; thermal shutdown prevents overheating during extended clinical monitoring sessions. |
| Automotive Body Control Units | Smart Home Hub Processors |
Use Scenario: Regulating power for LIN transceivers and door module MCUs in non-critical vehicle subsystems. IC Role / Device Role / Timing Role: Input-tolerant 3.3V LDO handling load-dump transients up to 20V with built-in overvoltage clamping. Use Value: Absolute max 20V input rating and SOA protection enable direct connection to 12V battery rail without pre-regulation. | Use Scenario: Providing stable core voltage to Wi-Fi/BLE SoCs and touch controller ASICs in always-on smart speakers and hubs. IC Role / Device Role / Timing Role: Compact D-PAK LDO replacing TO-220 variants to reduce board area while maintaining 0.5A delivery capability. Use Value: D-PAK footprint saves >60% PCB area vs. TO-220; 0.6V dropout preserves headroom for aging LiPo batteries. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MCP1700T-3302E/TT | 250mA max output, 6µA quiescent current, SOT-23 package | Lower current capacity; suited for ultra-low-power MCU sleep modes only | Select when <100mA load and <10µA IQ dominate design priorities over peak current |
| TPS7A4701RGWR | 1A output, 4µVrms noise, adjustable output, WQFN-20 package | Higher precision, lower noise, but requires external resistors and layout complexity | Select when sub-10µV noise and 0.01% VOUT accuracy justify added BOM and layout cost |
Compared with MCP1700T-3302E/TT and TPS7A4701RGWR, the KA78RM33TSTU uniquely balances 0.5A delivery, D-PAK thermal performance, and integrated protection - making it optimal for cost-sensitive industrial and automotive modules needing robustness without design overhead.
Availability
KA78RM33TSTU is available at Aetrix Electronics and suitable for industrial automation, portable medical devices, and automotive body electronics requiring stable component supply with consistent D-PAK packaging and short-lead form factor.
Supply support for KA78RM33TSTU 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
Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete solutions before its acquisition by ON Semiconductor in 2016.
The KA78RM33TSTU belongs to Fairchild's legacy fixed-output LDO family designed for cost-effective, high-reliability linear regulation in industrial and automotive environments where simplicity, thermal resilience, and protection integration are critical.
FAQ
What is the maximum input voltage rating for KA78RM33TSTU?
The KA78RM33TSTU has an absolute maximum input voltage of 20V, as specified in the Absolute Maximum Ratings table. This allows direct connection to 12V automotive or industrial bus systems with margin for transients. Operation above 16V is not recommended for continuous use due to thermal constraints and reduced safe operating area margin. The KA78RM33TSTU maintains regulation down to 4.3V input, enabling efficient use of intermediate rails.
Does KA78RM33TSTU require external capacitors for stability?
Yes, the KA78RM33TSTU requires external input and output capacitors for stable operation. A minimum 10µF ceramic capacitor is recommended at both VIN and VOUT pins, placed as close as possible to the device terminals. These capacitors ensure transient response integrity, reduce output impedance, and maintain phase margin - especially under dynamic load conditions. The KA78RM33TSTU is internally compensated, so no additional compensation network is needed.
Is KA78RM33TSTU pin-compatible with KA78RM33TU?
No, KA78RM33TSTU and KA78RM33TU are not pin-compatible. KA78RM33TSTU uses the D-PAK (TO-252) package with 3 leads and an exposed thermal pad, while KA78RM33TU uses the TO-220 package with 3 leads and a metal tab. Their footprints, thermal mounting, and mechanical dimensions differ significantly. Migration between them requires PCB redesign and thermal validation. The KA78RM33TSTU part number specifically denotes the short-lead D-PAK variant.
What protection features are integrated into KA78RM33TSTU?
The KA78RM33TSTU integrates four protection functions: overcurrent protection (limiting output to ~1A peak), thermal shutdown (activating at ~150°C junction temperature), Safe Operating Area (SOA) protection (preventing second breakdown during overload), and short-circuit protection (latching or foldback behavior depending on fault duration). These features are implemented on-die and require no external components - enhancing system reliability in unattended or harsh-environment deployments using KA78RM33TSTU.
Can KA78RM33TSTU be used in automotive applications?
Yes, KA78RM33TSTU is rated for operation from –25°C to +125°C ambient temperature and supports input voltages up to 20V, making it suitable for non-safety-critical automotive body electronics such as door modules, lighting controls, and HVAC interfaces. It meets basic automotive environmental requirements but is not AEC-Q100 qualified. For safety-critical systems (e.g., airbag, braking), a qualified alternative should be selected. KA78RM33TSTU's SOA and thermal shutdown provide robustness against load dumps and intermittent shorts commonly seen in vehicle electrical systems.
KA78RM33TSTU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-220-3
- Packaging:
- Tube
- Product Status:
- Obsolete
- Output Configuration:
- Positive
- Output Type:
- Fixed
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 20V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- 0.6V @ 500mA
- Current - Output:
- 500mA
- Current - Quiescent (Iq):
- 5 mA
- Current - Supply (Max):
- 10 mA
- PSRR:
- 55dB (120Hz)
- Control Features:
- -
- Protection Features:
- Over Current, Over Temperature, Short Circuit
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-3
KA78RM33TSTU FAQ
1.How can I place an order for KA78RM33TSTU through Aetrix?
Please submit a Request for Quotation (RFQ) for KA78RM33TSTU 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 KA78RM33TSTU reliable?
The price and inventory of KA78RM33TSTU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for KA78RM33TSTU is usually 5 days.
3.What payment methods are accepted for KA78RM33TSTU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for KA78RM33TSTU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for KA78RM33TSTU?
KA78RM33TSTU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your KA78RM33TSTU 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 KA78RM33TSTU?
For technical support, including KA78RM33TSTU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your KA78RM33TSTU requirements.
6.How does Aetrix verify that KA78RM33TSTU is sourced from the original manufacturer or authorized distributors?
All KA78RM33TSTU 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 KA78RM33TSTU meets industry standards.
7.What is the process for return or replacement of KA78RM33TSTU?
All KA78RM33TSTU units undergo pre-shipment inspection (PSI). If there is an issue with KA78RM33TSTU, 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 KA78RM33TSTU part is unused and in its original packaging.
Return procedure for KA78RM33TSTU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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