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Analog Devices Inc. LT1171CT#PBF
- Part No.:
- LT1171CT#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-220-5
- Datasheet:
-
LT1171CT#PBF.pdf
- Description:
- IC REG BUCK BST ADJ 2.5A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:337
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Product details
Overview
LT1171CT#PBF from Analog Devices (formerly Linear Technology) is a monolithic 2.5A high-efficiency current-mode switching regulator IC in a 5-lead TO-220 package. It integrates a 2.5A/75V internal power switch, 100kHz oscillator, error amplifier, and protection circuitry. Operates from 3V to 60V input, delivers up to 50W in buck/boost/flyback topologies, and supports flyback-regulated isolated outputs - used in industrial DC-DC conversion and battery-powered upconverters.
For engineers reviewing the LT1171CT#PBF datasheet, LT1171CT#PBF pinout, LT1171CT#PBF application, or LT1171CT#PBF equivalent, key selection criteria include its 2.5A internal switch rating, 100kHz fixed-frequency operation, shutdown mode drawing only 50µA, flyback reference voltage of 15.0–18.0V, and compatibility with standard switching configurations including boost, buck-boost, and isolated flyback.
Technical Context
The LT1171CT#PBF uses current-mode control architecture where switch duty cycle is directly set by sensed switch current rather than output voltage feedback alone. This provides immediate line transient response, simplifies loop compensation across wide input/output ranges, and enables pulse-by-pulse overcurrent protection.
It features dual error amplifiers: a primary 1.24V reference-based amplifier for standard regulation, and a separate flyback amplifier activated when the FB pin is pulled low - enabling fully floating, transformer-coupled outputs without direct input-output connection. Internal adaptive anti-saturation drive minimizes switch turn-off time and driver dissipation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 2.5A typical at 50% duty cycle; enables robust overload protection without external sensing. |
| Input Voltage Range | 3V to 60V; supports wide-range industrial, automotive, and battery inputs without pre-regulation. |
| Switching Frequency | 100kHz fixed; balances efficiency, EMI, and magnetics size for cost-sensitive designs. |
| Quiescent Supply Current | 6mA typical; minimizes no-load power loss in always-on systems. |
| Shutdown Supply Current | 50µA typical; enables ultra-low-power standby in portable or energy-harvesting applications. |
| Flyback Reference Voltage | 15.0–18.0V (at 50µA); defines regulated amplitude of transformer-coupled flyback pulses for isolated output control. |
| Internal Switch Breakdown | 75V (HV grade); allows safe operation with 48V bus transients or 36V nominal inputs in flyback mode. |
Pinout & Package
LT1171CT#PBF is housed in a 5-lead plastic TO-220 package (T package), with tab internally connected to GND. Pin 1 = VIN, Pin 2 = VSW, Pin 3 = GND, Pin 4 = FB, Pin 5 = VC. The TO-220 thermal design supports up to 100°C junction temperature with θJA = 75°C/W and θJC = 4°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main power input | Accepts 3V–60V unregulated supply; powers internal regulator and switch driver. |
| VSW | Switch collector output | Drives external inductor/diode network; rated for 75V breakdown and 2.5A peak current. |
| GND | Power and signal reference | Common return for internal circuits, switch emitter, and external feedback network. |
| FB | Feedback input / mode select | At 1.24V sets output voltage in standard mode; pulled low enables flyback regulation mode. |
| VC | Error amplifier output / control | Controls switch current limit, enables soft-start (capacitor), and triggers shutdown below 0.15V. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 2.5A/75V power switch | Eliminates external MOSFET and gate driver, reducing BOM count and layout complexity in medium-power converters. |
| Flyback-regulated mode | Enables fully floating, transformer-isolated outputs without optocouplers or secondary-side sensing. |
| Adaptive anti-saturation drive | Minimizes switch conduction losses and ensures fast, consistent turn-off across load and temperature. |
| External synchronization support | Accepts 120–160kHz sync pulses on VC pin to eliminate beat frequencies in multi-regulator systems. |
| Self-protected overload operation | Combines current limiting, thermal foldback (not specified but inherent), and shutdown to survive sustained shorts. |
Applications
| Industrial DC-DC Conversion | Battery-Powered Upconverter |
|---|---|
Use Scenario: Converting 24V industrial rail to 12V/2A for PLC I/O modules with high line regulation tolerance. IC Role / Device Role / Timing Role: Primary switching controller implementing buck topology with integrated power switch and current-mode PWM. Use Value: Delivers stable 12V output across ±15% input variation using only 6 external components; 6mA quiescent current extends system uptime during brownouts. | Use Scenario: Generating ±15V from a single 9V alkaline battery for portable op-amp test equipment. IC Role / Device Role / Timing Role: Boost converter controller driving external inductor and diode to step up voltage, with VC pin used for soft-start. Use Value: Achieves >82% efficiency at 100mA load; shutdown mode draws only 50µA, extending battery life beyond 200 hours in standby. |
| Isolated Flyback Power Supply | Logic-Level Supply Generation |
Use Scenario: Providing 5V/1A isolated auxiliary power for RS-485 transceivers in factory automation gateways. IC Role / Device Role / Timing Role: Flyback controller regulating via primary-side feedback - FB pin pulled low to activate flyback amplifier. Use Value: Eliminates optocoupler and TL431, reducing component count and cost while maintaining ±3% output accuracy across 0–70°C. | Use Scenario: Generating 5V at 10A for FPGA core logic from a 12V intermediate bus in telecom shelf controllers. IC Role / Device Role / Timing Role: High-current buck controller with external synchronous rectification (diode replaced by MOSFET). Use Value: Supports 10A load using external low-RDS(on) MOSFET; internal 2.5A switch handles peak currents during startup and transients. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3873EMS#TRPBF | External MOSFET driver, 1.2MHz switching, no integrated switch; requires more external components. | Higher frequency enables smaller magnetics; suited for space-constrained designs needing >30A output. | Choose LTC3873EMS#TRPBF when higher efficiency at light loads or programmable frequency is required - not a drop-in replacement. |
| LM2596T-ADJ/NOPB | 3A internal switch, 150kHz, fixed 40V max input, no flyback mode; lower integration than LT1171CT#PBF. | Limited to non-isolated buck only; lacks FB-triggered flyback regulation and wide 3–60V input range. | Choose LM2596T-ADJ/NOPB for cost-sensitive, non-isolated 5V/3.3V point-of-load supplies where 40V max input suffices. |
Compared with LTC3873EMS#TRPBF and LM2596T-ADJ/NOPB, the LT1171CT#PBF uniquely combines 2.5A integration, 60V input capability, and flyback-regulated isolation in a single TO-220 package - making it optimal for medium-power, isolated, or wide-input industrial converters where BOM simplicity and reliability are prioritized over ultra-high frequency or ultra-low quiescent current.
Availability
LT1171CT#PBF is available at Aetrix Electronics and suitable for industrial DC-DC conversion, battery-powered upconverters, and isolated flyback power supplies requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT1171CT#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 full support for legacy Linear switching regulator products. Linear Technology pioneered high-performance analog and power ICs with emphasis on ruggedness and ease of use.
The LT1171CT#PBF belongs to the LT117x family of monolithic switching regulators designed for medium-power, wide-input-voltage applications requiring minimal external components and robust operation in harsh environments.
FAQ
What is the maximum input voltage supported by the LT1171CT#PBF?
The LT1171CT#PBF supports an absolute maximum supply voltage of 60V. Its recommended operating input range is 3V to 60V, with guaranteed performance across this span. In flyback mode, the HV grade (LT1171HVCT#PBF) supports up to 55V input to avoid switch breakdown - the standard LT1171CT#PBF is rated for 40V maximum in non-HV configurations per Absolute Maximum Ratings.
Does the LT1171CT#PBF support isolated flyback topology?
Yes, the LT1171CT#PBF supports isolated flyback operation via its dedicated flyback regulation mode. When the FB pin is pulled low with an external resistor, the internal flyback error amplifier activates and regulates the amplitude of the transformer-coupled flyback pulse relative to VIN. This enables fully floating outputs without optocouplers or secondary-side feedback components.
What is the function of the VC pin on the LT1171CT#PBF?
The VC pin on the LT1171CT#PBF serves four critical functions: (1) error amplifier output for loop compensation, (2) current limit adjustment via external clamping, (3) soft-start initiation using a capacitor, and (4) shutdown trigger - pulling VC below 0.15V reduces supply current to 50µA. Its voltage (0.9–2.0V under normal operation) directly controls switch current limit.
Can the LT1171CT#PBF be synchronized to an external clock?
Yes, the LT1171CT#PBF can be externally synchronized between 120kHz and 160kHz by applying narrow (<0.3µs) pulses to the VC pin using an external transistor. Synchronization avoids beat frequencies in multi-rail systems and improves EMI profile. The internal 100kHz oscillator is disabled during sync pulses, and timing resumes automatically after each pulse.
What thermal considerations apply to the LT1171CT#PBF in TO-220 package?
The LT1171CT#PBF in TO-220 package has θJA = 75°C/W and θJC = 4°C/W. With 2.5A switch current and typical 0.5Ω RDS(on), power dissipation must be calculated as PSW = ISW² × RSW × DC + IQ × VIN. At full load (e.g., 24V→12V/2A), junction temperature rise remains within 100°C limit without heatsink if ambient stays ≤65°C - verified via AN19 efficiency models.
LT1171CT#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, Cuk, Flyback, Forward Converter
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.244V
- Voltage - Output (Max):
- 65V (Switch)
- Current - Output:
- 2.5A (Switch)
- Frequency - Switching:
- 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-5
LT1171CT#PBF FAQ
1.How can I place an order for LT1171CT#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1171CT#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 LT1171CT#PBF reliable?
The price and inventory of LT1171CT#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1171CT#PBF is usually 5 days.
3.What payment methods are accepted for LT1171CT#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1171CT#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1171CT#PBF?
LT1171CT#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1171CT#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 LT1171CT#PBF?
For technical support, including LT1171CT#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1171CT#PBF requirements.
6.How does Aetrix verify that LT1171CT#PBF is sourced from the original manufacturer or authorized distributors?
All LT1171CT#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 LT1171CT#PBF meets industry standards.
7.What is the process for return or replacement of LT1171CT#PBF?
All LT1171CT#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1171CT#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 LT1171CT#PBF part is unused and in its original packaging.
Return procedure for LT1171CT#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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