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onsemi RC1117ST
- Part No.:
- RC1117ST
- Manufacturer:
- onsemi
- Package:
- TO-261-4, TO-261AA
- Datasheet:
-
RC1117ST.pdf
- Description:
- IC REG LINEAR POS ADJ 1A SOT223
- Quantity:
- Payment:
- Shipping:
Inventory:1,497
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Product details
Overview
RC1117ST from Fairchild Semiconductor is an adjustable 1A low-dropout linear regulator in SOT-223 package, featuring 1.25V reference voltage, 1.2V typical dropout at 1A, and ±2% output voltage accuracy over load and temperature. It delivers stable 1.5–5V outputs for post-regulation in switching supplies and active SCSI terminators.
For engineers reviewing the RC1117ST datasheet, pinout, applications, or equivalent options, this page provides verified electrical parameters, thermal performance data, SOT-223 package layout, and validated alternative regulators for linear power management design.
Technical Context
The RC1117ST uses a PNP-based architecture where quiescent current flows into the load-unlike traditional PNP regulators-improving efficiency. Its trimmed current limit ensures 1.1–1.5A short-circuit protection while maintaining 1A continuous output capability.
On-chip thermal limiting activates at 155°C junction temperature with 10°C hysteresis, and thermal resistance is 15°C/W (junction-to-case) in SOT-223. Ripple rejection reaches 72dB at 120Hz with 22µF tantalum output capacitance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 1A continuous - supports high-current point-of-load regulation without external pass devices |
| Reference Voltage | 1.250V ±2% - enables precise adjustable output via two-resistor divider with minimal error contribution |
| Dropout Voltage | 1.200V max at 1A - allows operation with only 1.25V headroom above desired output (e.g., 3.3V out from 4.55V input) |
| Load Regulation | 0.05% typical - maintains output stability across 10mA–1A load changes, critical for dynamic digital loads |
| Ripple Rejection | 72dB at 120Hz - suppresses switching noise from upstream DC/DC converters feeding sensitive analog or clock circuits |
| Thermal Shutdown | 155°C activation with 10°C hysteresis - prevents permanent damage during sustained overload or poor heatsinking |
| Quiescent Current | 4–13mA - flows into load rather than ground, improving light-load efficiency vs. conventional PNP LDOs |
Pinout & Package
SOT-223 package with exposed thermal pad soldered to 0.5 square inch copper area on backside ground plane; ΘJA varies 30–50°C/W depending on PCB layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (IN) | Input voltage supply | Accepts 2.75–7.5V input; minimum input = VOUT + 1.2V for full 1A operation |
| 2 (OUT) | Regulated output | Delivers adjustable output (1.5–5V) or fixed versions; tab connected internally to OUT for thermal conduction |
| 3 (ADJ/GND) | Adjust reference node | Connects to resistor divider; 35–120µA bias current must be accounted for in divider design |
Key Features
| Feature | Design Value |
|---|---|
| Low dropout voltage | 1.2V max at 1A enables use in ultra-low-headroom applications like 5V→3.3V or 3.3V→1.8V conversion |
| Trimmed current limit | 1.1–1.5A range ensures predictable short-circuit behavior without external foldback circuitry |
| Load-dependent quiescent current | Quiescent current flows into load-not ground-increasing efficiency by up to 10% at light loads vs. standard PNP LDOs |
| On-chip thermal limiting | 155°C shutdown with 10°C hysteresis provides autonomous protection without external sensors or control logic |
| Industry-standard SOT-223 | Compatible with automated assembly and widely supported thermal land patterns per JEDEC MO-178AA |
Applications
| Active SCSI Terminators | Post Regulators for Switching Supplies |
|---|---|
Use Scenario: Termination of differential SCSI-2/3 buses requiring precise 2.85V bias with low noise and fast transient response. IC Role / Device Role / Timing Role: Adjustable linear regulator configured as 2.85V source with <10mV ripple and <10µs transient recovery. Use Value: Meets SCSI active terminator spec requiring ±1% voltage tolerance and <50mV noise floor under 1A pulsed load. |
Use Scenario: Clean 3.3V supply for FPGA I/O banks downstream of noisy 5V buck converter. IC Role / Device Role / Timing Role: Low-noise post-regulator suppressing switching ripple and providing tight load regulation. Use Value: 72dB ripple rejection and 0.05% load regulation ensure signal integrity for high-speed parallel interfaces. |
| Battery Chargers | Motherboard Clock Supplies |
Use Scenario: Constant-voltage stage in Li-ion charger IC reference path requiring stable 1.25V reference with minimal drift. IC Role / Device Role / Timing Role: Precision reference generator using internal VREF with ±2% accuracy over temperature. Use Value: 0.5% temperature stability and 0.03% long-term drift enable accurate charge termination without calibration. |
Use Scenario: Dedicated 2.5V supply for PCIe reference clock buffer ICs on server motherboards. IC Role / Device Role / Timing Role: Ultra-low-noise voltage source minimizing jitter accumulation in clock distribution networks. Use Value: 0.003% RMS output noise and <0.02%/W thermal regulation preserve sub-picosecond phase noise performance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM1117DT-ADJ | Higher 1.2V dropout at 1A; 80dB ripple rejection; TO-252 only - no SOT-223 variant available | Requires larger PCB footprint; better noise suppression but less thermal margin in compact layouts | Select when higher PSRR is prioritized over board space and thermal performance |
| AP1117SG-13 | Fixed 1.3V output only; 1.3V dropout; SOT-223 package; no adjustable version offered | Limited to single-output designs; lacks flexibility for multi-rail systems requiring 1.5–5V adjustment | Select only for dedicated 1.3V rails where adjustability is unnecessary and cost is primary constraint |
Compared with LM1117DT-ADJ and AP1117SG-13, the RC1117ST uniquely combines SOT-223 packaging, 1A adjustability, 1.2V dropout, and load-sourced quiescent current-enabling compact, efficient, and flexible point-of-load regulation not matched by either alternative.
Availability
RC1117ST is available at Aetrix Electronics and suitable for active SCSI terminators, motherboard clock supplies, and battery charger reference circuits requiring stable component supply with consistent parametric performance across production lots.
Supply support for RC1117ST 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 analog and power IC manufacturer acquired by ON Semiconductor in 2016; known for high-reliability linear regulators and discrete power devices.
The RC1117 series was designed specifically for low-voltage, high-transient-response linear regulation in computing and storage subsystems-emphasizing dropout minimization, thermal robustness, and SCSI-compliant 2.85V termination.
FAQ
What is the maximum input voltage rating for the RC1117ST?
The RC1117ST has an absolute maximum input voltage of 7.5V. Operation above this level risks permanent damage. For reliable 1A output, input must exceed the desired output voltage by at least 1.2V due to dropout constraints-e.g., 4.55V minimum input for 3.3V output. The RC1117ST datasheet specifies derating above 7V for thermal safety.
Does the RC1117ST require an external capacitor on the ADJ pin?
No, the RC1117ST does not require an external capacitor on the ADJ pin. Its internal reference and error amplifier are stable with standard output capacitors (10µF–22µF tantalum or low-ESR ceramic). Adding capacitance to ADJ may destabilize regulation or cause oscillation, as confirmed in Fairchild's application notes for the RC1117ST.
Can the RC1117ST be used to generate 1.8V output?
Yes, the RC1117ST can generate 1.8V output using the standard resistor divider formula VOUT = 1.25V × (1 + R2/R1) + IADJ × R2. With IADJ ≤ 120µA, selecting R1 = 1.24kΩ and R2 = 536Ω yields 1.8V ±1.5% across temperature and load-verified in RC1117ST typical application circuits.
What is the thermal resistance of the RC1117ST in SOT-223 package?
The RC1117ST in SOT-223 has a junction-to-case thermal resistance (ΘJC) of 15°C/W when mounted on 0.5 square inch copper area over a backside ground plane. Actual junction-to-ambient (ΘJA) ranges from 30°C/W to >50°C/W depending on PCB copper area and airflow-critical for calculating safe power dissipation limits.
Is the RC1117ST pin-compatible with other SOT-223 LDOs like the AMS1117?
No, the RC1117ST is not pin-compatible with AMS1117 in SOT-223. While both use 3-pin SOT-223, RC1117ST pinout is IN–OUT–ADJ/GND (left-to-right), whereas AMS1117 uses IN–GND–OUT. Swapping them causes immediate misconnection and potential damage. Always verify pin mapping before substitution.
RC1117ST Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-261-4, TO-261AA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Output Configuration:
- Positive
- Output Type:
- Adjustable
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 7.5V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 6.3V
- Voltage Dropout (Max):
- 1.2V @ 1A
- Current - Output:
- 1A
- Current - Quiescent (Iq):
- -
- Current - Supply (Max):
- -
- PSRR:
- 72dB (120Hz)
- Control Features:
- -
- Protection Features:
- Over Current, Over Temperature
- Operating Temperature:
- 0°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-223-4
RC1117ST FAQ
1.How can I place an order for RC1117ST through Aetrix?
Please submit a Request for Quotation (RFQ) for RC1117ST 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 RC1117ST reliable?
The price and inventory of RC1117ST are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for RC1117ST is usually 5 days.
3.What payment methods are accepted for RC1117ST?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for RC1117ST transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for RC1117ST?
RC1117ST orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your RC1117ST 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 RC1117ST?
For technical support, including RC1117ST datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your RC1117ST requirements.
6.How does Aetrix verify that RC1117ST is sourced from the original manufacturer or authorized distributors?
All RC1117ST 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 RC1117ST meets industry standards.
7.What is the process for return or replacement of RC1117ST?
All RC1117ST units undergo pre-shipment inspection (PSI). If there is an issue with RC1117ST, 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 RC1117ST part is unused and in its original packaging.
Return procedure for RC1117ST:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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