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Analog Devices Inc. LT1171IQ#PBF
- Part No.:
- LT1171IQ#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Datasheet:
-
LT1171IQ#PBF.pdf
- Description:
- IC REG BUCK BST ADJ 2.5A DDPAK-5
- Quantity:
- Payment:
- Shipping:
Inventory:181
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Product details
Overview
LT1171IQ#PBF from Analog Devices (formerly Linear Technology) is a monolithic 2.5A high-efficiency current-mode switching regulator IC in a 5-lead plastic TO-220 package. It operates from 3V to 60V input, delivers up to 50W output power, integrates a 2.5A/75V internal switch, and supports buck, boost, flyback, inverting, and Cuk topologies for industrial DC-DC conversion.
For engineers reviewing the LT1171IQ#PBF datasheet, LT1171IQ#PBF pinout, LT1171IQ#PBF application, or LT1171IQ#PBF equivalent, this page provides verified pin functions, topology-specific design meaning, thermal derating guidance for –40°C to 100°C operation, and validated alternative parts with documented current-limit and package differences.
Technical Context
The LT1171IQ#PBF uses current-mode control with adaptive anti-saturation drive, enabling stable regulation across wide load ranges without efficiency loss. Its 100kHz fixed-frequency oscillator synchronizes externally from 120–160kHz, and its dual error amplifier supports both normal (1.24V reference) and isolated flyback modes (15V reference).
It features a shutdown mode reducing supply current to 50µA, internal 2.3V bias regulator for wide VIN operation, and VC pin functionality for soft-start, current limit adjustment, and total shutdown - all implemented without external compensation components in basic configurations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 2.5A typical at 50% duty cycle; enables 50W output in buck/boost with proper heatsinking |
| Input Voltage Range | 3V to 60V; supports wide-range industrial inputs including 12V/24V/48V systems |
| Quiescent Current | 6mA typical; ensures low standby loss in always-on power supplies |
| Shutdown Current | 50µA typical; allows battery-backed systems to maintain >1-year shelf life |
| Switch Breakdown Voltage | 75V; permits safe operation with 48V nominal inputs plus transients |
| Switch "On" Resistance | 0.3Ω max; limits conduction loss to ≤1.875W at 2.5A full load |
| Reference Voltage | 1.24V ±20mV; sets output accuracy in non-isolated topologies |
Pinout & Package
LT1171IQ#PBF uses a 5-lead plastic TO-220 package (T package) with tab connected to GND. Thermal resistance θJA = 75°C/W; requires minimum 0.5 sq. in. copper pour for full 2.5A operation at 100°C ambient.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input Supply | Accepts 3V–60V unregulated input; connects directly to bulk capacitor |
| VSW | Switch Output | Drives external inductor/diode; handles 2.5A peak current and 75V transient |
| GND | Power & Signal Ground | Common return for input, output, and internal circuitry; tab is electrically tied to this pin |
| FB | Feedback Input | Senses output voltage divider; 1.24V threshold enables precise regulation or flyback mode selection |
| VC | Error Amplifier Output | Controls duty cycle via current-mode loop; used for soft-start, current limiting, and shutdown |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 2.5A/75V Power Switch | Eliminates external MOSFET in ≤50W designs, reducing BOM count and layout complexity |
| Flyback-Regulated Mode | Enables fully floating outputs up to transformer breakdown voltage without optocoupler feedback |
| Adaptive Anti-Saturation Drive | Maintains high efficiency across 0.1A–2.5A load range by dynamically adjusting gate drive |
| External Synchronization | Allows noise-sensitive systems to lock switching frequency to 120–160kHz clock source |
| Self-Protected Overload Handling | Current-mode architecture provides inherent pulse-by-pulse limiting during short-circuit events |
Applications
| Industrial DC-DC Conversion | Battery-Powered Upconversion |
|---|---|
Use Scenario: Converting 24V rail to 15V for PLC I/O modules in factory automation cabinets. IC Role / Device Role / Timing Role: Primary switching regulator in non-isolated buck configuration with 100kHz fixed-frequency operation. Use Value: Delivers 2.5A continuous output with <1% line regulation over 20–30V input variation, minimizing need for post-regulation LDOs. | Use Scenario: Boosting 3.6V Li-ion battery to 12V for portable test equipment display backlight. IC Role / Device Role / Timing Role: High-efficiency boost converter operating down to 3V input with programmable soft-start. Use Value: Achieves >88% efficiency at 1A load while maintaining regulation until battery drops to 3.0V, extending runtime. |
| Floating Dual-Output Supplies | High-Voltage Logic Supply |
Use Scenario: Generating ±15V op-amp rails from 48V telecom bus in signal conditioning front-end. IC Role / Device Role / Timing Role: Flyback controller with transformer-coupled secondary windings and no optocoupler. Use Value: Provides fully isolated ±15V outputs with <±3% cross-regulation and 1500V isolation barrier per IEC 60950. | Use Scenario: Powering 5V logic and 10A FPGA core voltage from 12V intermediate bus in embedded computing. IC Role / Device Role / Timing Role: Synchronous buck controller driving external high-current MOSFETs (not applicable here - LT1171IQ#PBF is self-contained). Use Value: Not applicable - LT1171IQ#PBF is a monolithic regulator, not a controller; this application requires external FETs and is outside its capability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1170IQ#PBF | 5A switch current rating vs. 2.5A; identical pinout and package; higher RDS(on) (0.15Ω vs. 0.3Ω) improves conduction loss at high current | Supports up to 100W output; requires larger heatsink for same thermal margin | Select when ≥3.5A peak load or >75W output is required; verify PCB copper area supports higher dissipation |
| LT1172CN8#PBF | 1.25A switch rating; 8-pin PDIP package; separate E1/E2 emitter pins enable current-limit tuning; no TO-220 thermal path | Limited to ≤25W; suited for space-constrained low-power designs where isolation or compact footprint is prioritized | Select for cost-sensitive, lower-power applications (<1.5A) where TO-220 mounting is impractical |
Compared with LT1171IQ#PBF, LT1170IQ#PBF doubles output current capacity but increases conduction loss at light loads, while LT1172CN8#PBF trades current capability for package flexibility and fine-grained current limiting - making LT1171IQ#PBF the optimal balance for 2–3A industrial DC-DC needs.
Availability
LT1171IQ#PBF is available at Aetrix Electronics and suitable for industrial automation, battery-powered instrumentation, and telecom power conversion requiring stable component supply, extended temperature support (–40°C to 100°C), and long-term lifecycle continuity.
Supply support for LT1171IQ#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 technical support, manufacturing, and documentation for the LT117x family.
The LT117x series was designed as monolithic high-power switching regulators to replace multi-chip discrete solutions in rugged industrial and telecom power supplies, emphasizing integration, fault tolerance, and topology flexibility.
FAQ
What is the maximum continuous output power achievable with LT1171IQ#PBF in boost configuration?
The LT1171IQ#PBF supports up to 50W continuous output power in boost mode under proper thermal management. At 24V input and 48V output, it delivers 1.04A (50W) with >85% efficiency. Derating is required above 70°C ambient due to its 75°C/W θJA; full 2.5A switch current is only sustainable below 50°C ambient with standard TO-220 copper pour.
Can LT1171IQ#PBF be used in flyback topology without an optocoupler?
Yes, LT1171IQ#PBF supports optocoupler-free flyback regulation using its dedicated flyback mode. When the FB pin is pulled below 0.45V, it activates the internal 15V flyback reference and regulates the reflected flyback pulse amplitude - enabling fully floating outputs with transformer isolation and no secondary-side feedback components.
What thermal considerations apply to LT1171IQ#PBF in a sealed enclosure?
In sealed enclosures, LT1171IQ#PBF requires ≥1.2 sq. in. of 1oz copper on the TO-220 tab side and forced airflow ≥100LFM to sustain 2.5A output at 100°C ambient. Without airflow, maximum ambient must be limited to 65°C to prevent junction temperature exceeding 125°C, based on its 75°C/W θJA and 0.3Ω RDS(on).
How does the VC pin function in shutdown mode for LT1171IQ#PBF?
When the VC pin voltage is pulled below 0.15V (e.g., via resistor to ground), LT1171IQ#PBF enters full shutdown mode, reducing supply current to 50µA. The internal switch disables, FB amplifier disconnects, and oscillator halts - preserving battery life while allowing rapid wake-up by releasing the VC pin.
Is LT1171IQ#PBF pin-compatible with LT1170IQ#PBF or LT1172CN8#PBF?
LT1171IQ#PBF is pin-compatible with LT1170IQ#PBF in the same TO-220 package (same pinout, same footprint), but not with LT1172CN8#PBF, which uses an 8-pin DIP package with different pin assignment and separate emitter terminals (E1/E2). Swapping LT1171IQ#PBF for LT1170IQ#PBF requires verifying thermal design for higher current.
LT1171IQ#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- 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:
- -40°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DDPAK-5
LT1171IQ#PBF FAQ
1.How can I place an order for LT1171IQ#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1171IQ#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 LT1171IQ#PBF reliable?
The price and inventory of LT1171IQ#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1171IQ#PBF is usually 5 days.
3.What payment methods are accepted for LT1171IQ#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1171IQ#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1171IQ#PBF?
LT1171IQ#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1171IQ#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 LT1171IQ#PBF?
For technical support, including LT1171IQ#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1171IQ#PBF requirements.
6.How does Aetrix verify that LT1171IQ#PBF is sourced from the original manufacturer or authorized distributors?
All LT1171IQ#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 LT1171IQ#PBF meets industry standards.
7.What is the process for return or replacement of LT1171IQ#PBF?
All LT1171IQ#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1171IQ#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 LT1171IQ#PBF part is unused and in its original packaging.
Return procedure for LT1171IQ#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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