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Analog Devices Inc. LT1271CT#PBF
- Part No.:
- LT1271CT#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-220-5
- Datasheet:
-
LT1271CT#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 4A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:132
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Product details
Overview
LT1271CT#PBF from Analog Devices (formerly Linear Technology) is a monolithic 4A, 60kHz switching regulator IC in TO-220-5 package, integrating high-current switch, oscillator, current-mode control, and thermal/overload protection. It operates from 3.5V to 30V input, delivers up to 3A at 5V in buck mode, and supports boost, flyback, and inverting configurations for PC power supplies and battery up-converters.
For engineers reviewing the LT1271CT#PBF datasheet, LT1271CT#PBF pinout, LT1271CT#PBF application, or LT1271CT#PBF equivalent, key selection criteria include its 4A internal switch rating, 60kHz fixed frequency, 7mA quiescent current, shutdown threshold of 100µA, and compatibility with standard buck/boost/flyback topologies requiring minimal external components.
Technical Context
The LT1271CT#PBF uses current-mode switching architecture with adaptive antisaturation gate drive, enabling stable operation across wide load ranges without efficiency loss. Its error amplifier features 1.244V reference voltage, 4400 µmho transconductance, and ±25µA output current capability for precise feedback control.
It implements patented burst-mode operation for light-load efficiency, supports external synchronization via VC pin, and includes flyback-regulated mode with fully floating outputs. Shutdown activation reduces supply current to 100µA while maintaining 100mV threshold hysteresis.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 60kHz typical - sets minimum inductor size and EMI profile for buck/boost designs |
| Internal Switch Current | 4A maximum - enables single-chip 3A output in buck mode without external MOSFET |
| Input Voltage Range | 3.5V to 30V - supports 5V/12V/24V rails and wide automotive/battery inputs |
| Quiescent Current | 7mA typical - minimizes no-load power loss in always-on systems |
| Reference Voltage | 1.244V ±20mV - defines output accuracy in feedback loop; stable over temperature |
| Shutdown Current | 100µA typical - enables low-power standby in battery-powered applications |
| Max Duty Cycle | 92% - allows high step-down ratios in buck configuration with margin |
Pinout & Package
LT1271CT#PBF is housed in a 5-lead plastic TO-220 package with exposed tab for thermal dissipation (θJC = 4°C/W). The tab is electrically connected to GND and requires insulated mounting when used on heatsinks.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Power Input | Primary DC input connection (3.5V–30V); decoupling capacitor required near pin |
| VSW | Switch Output | Drives external inductor/diode; connects to internal 4A N-channel switch drain |
| GND | Ground Reference | Power and signal ground; tied to TO-220 tab; must be low-impedance plane |
| FB | Feedback Input | Monitors output voltage via resistor divider; regulates to 1.244V reference |
| VC | Control Voltage | Enables shutdown (≤0.5V), burst mode (open), or external sync (AC-coupled) |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 4A Power Switch | Eliminates need for external MOSFET and driver in ≤3A buck/boost designs |
| Current-Mode Control | Provides inherent cycle-by-cycle current limiting and fast transient response |
| Flyback-Regulated Mode | Supports isolated outputs with fully floating secondary windings and no optocoupler |
| Adaptive Antisaturation Drive | Maintains high efficiency across 0.1A–3A load range without external compensation |
| Self-Protected Operation | Includes thermal shutdown, current limit, and safe operating area (SOA) protection |
Applications
| PC Power Supply | Battery Up-Converter |
|---|---|
Use Scenario: Generating +5V/3A and +12V outputs from 24V rail in compact desktop or embedded PC PSU. IC Role / Device Role / Timing Role: Primary switching regulator in non-isolated buck and flyback stages; provides regulation and overload protection. Use Value: Enables "bust-proof" operation with only 5 external parts per output, reducing BOM count and layout complexity. | Use Scenario: Boosting single-cell Li-ion (3.0–4.2V) to stable 5V USB power for portable instrumentation. IC Role / Device Role / Timing Role: High-efficiency boost controller with 60kHz fixed frequency and 7mA quiescent current. Use Value: Delivers >90% efficiency at 0.4–1.5A loads while drawing only 100µA in shutdown-extending battery life. |
| Negative-to-Positive Converter | Industrial Buck Converter |
Use Scenario: Converting –12V rail to +12V/1.5A output in legacy test equipment with dual-supply requirements. IC Role / Device Role / Timing Role: Inverting buck-boost regulator using transformer-coupled topology with floating FB reference. Use Value: Achieves fully isolated, polarity-inverted output without optocouplers or secondary-side regulation circuitry. | Use Scenario: Providing 5.2V/3.5A from –8V to –30V input in industrial motor control I/O modules. IC Role / Device Role / Timing Role: Negative-input buck regulator with VC-controlled shutdown and thermal foldback. Use Value: Supports wide negative input range and delivers high output current with integrated SOA protection. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1374CS8#PBF | 500kHz switching, 4.5A switch, SO-8 package, VIN ≤ 25V | Higher frequency enables smaller magnetics; not suitable for >25V input or TO-220 thermal mass needs | Choose for space-constrained PCBs needing faster transient response and lower EMI filtering burden |
| LT1171CT#PBF | 100kHz, 2.5A switch, same TO-220-5 package, wider 40V input range | Lower current rating limits output to ~2A; better for high-input-voltage industrial sensors | Choose when input exceeds 30V or thermal budget allows lower peak current density |
Compared with LT1374CS8#PBF and LT1171CT#PBF, the LT1271CT#PBF offers optimal balance of 4A capability, 30V input support, and TO-220 thermal performance for medium-power industrial and computing applications where board area is less constrained than in portable designs.
Availability
LT1271CT#PBF is available at Aetrix Electronics and suitable for PC power supplies, battery up-converters, negative-to-positive converters, and industrial buck regulators requiring stable component supply and long-term manufacturability.
Supply support for LT1271CT#PBF 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
Analog Devices acquired Linear Technology in 2017 and maintains its high-performance analog and power management portfolio.
The LT1271CT#PBF belongs to Linear's monolithic switching regulator product line, designed for medium-power DC/DC conversion in industrial, computing, and battery-powered systems where integration, reliability, and thermal robustness are critical.
FAQ
What is the maximum output current achievable with LT1271CT#PBF in buck configuration?
The LT1271CT#PBF supports up to 3A continuous output in buck mode, based on its 4A internal switch rating, thermal limits of the TO-220 package (θJA = 50°C/W), and typical efficiency of ~90% at 0.4–1.5A. Derating is required above 25°C ambient or with inadequate heatsinking; full 3A output assumes ≥2.5 cm² copper pour and forced airflow.
Does LT1271CT#PBF support synchronous rectification?
No, the LT1271CT#PBF does not support synchronous rectification. It drives an external diode (e.g., MBR340) in standard buck/boost configurations and relies on Schottky or fast recovery diodes for output rectification. Its VSW pin is designed for nonsynchronous operation with diode-based freewheeling paths.
Can LT1271CT#PBF be used in flyback mode with isolated outputs?
Yes, the LT1271CT#PBF supports flyback-regulated mode with fully floating outputs. In this configuration, the FB pin references the secondary-side winding, enabling regulation without optocouplers or TL431 circuits. The datasheet confirms "flyback regulated mode has fully floating outputs" and provides application circuits for isolated ±12V generation.
What is the purpose of the VC pin on LT1271CT#PBF?
The VC pin on LT1271CT#PBF serves three functions: (1) shutdown activation when pulled ≤0.5V (reducing supply current to 100µA), (2) burst-mode operation when left open, and (3) external synchronization when driven with AC-coupled square wave. Its 0.9V typical threshold ensures clean mode transitions and noise immunity in noisy environments.
Is LT1271CT#PBF RoHS compliant and lead-free?
Yes, LT1271CT#PBF is RoHS compliant and lead-free. The "#PBF" suffix explicitly denotes lead-free packaging per Analog Devices' product marking convention. It meets JEDEC J-STD-020 moisture sensitivity level 3 and is qualified for reflow soldering with peak temperatures up to 260°C.
LT1271CT#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- TO-220-5
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost, Buck-Boost, Flyback
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.5V
- Voltage - Input (Max):
- 30V
- Voltage - Output (Min/Fixed):
- 1.244V
- Voltage - Output (Max):
- 60V (Switch)
- Current - Output:
- 4A (Switch)
- Frequency - Switching:
- 60kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 100°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-5
LT1271CT#PBF FAQ
1.How can I place an order for LT1271CT#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1271CT#PBF 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 LT1271CT#PBF reliable?
The price and inventory of LT1271CT#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1271CT#PBF is usually 5 days.
3.What payment methods are accepted for LT1271CT#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1271CT#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1271CT#PBF?
LT1271CT#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1271CT#PBF 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 LT1271CT#PBF?
For technical support, including LT1271CT#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1271CT#PBF requirements.
6.How does Aetrix verify that LT1271CT#PBF is sourced from the original manufacturer or authorized distributors?
All LT1271CT#PBF 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 LT1271CT#PBF meets industry standards.
7.What is the process for return or replacement of LT1271CT#PBF?
All LT1271CT#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1271CT#PBF, 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 LT1271CT#PBF part is unused and in its original packaging.
Return procedure for LT1271CT#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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