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Analog Devices Inc. LT1071CT#PBF
- Part No.:
- LT1071CT#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-220-5
- Datasheet:
-
LT1071CT#PBF.pdf
- Description:
- IC REG BUCK BST ADJ 2.5A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:225
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Product details
Overview
LT1071CT#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 supports buck, boost, flyback, forward, inverting, and Cuk topologies; operates from 3V to 60V input; delivers up to 50W output power; and integrates a 2.5A internal switch with adaptive antisaturation drive, 40kHz oscillator, error amplifier, and protection circuitry. It is used in off-line converters, battery upconverters, and isolated dual-polarity supplies.
For engineers reviewing the LT1071CT#PBF datasheet, LT1071CT#PBF pinout, LT1071CT#PBF application, or LT1071CT#PBF equivalent, this page provides verified technical context, topology-specific design meaning, real-world application cards, and validated alternative parts - all grounded in the official Linear Technology 10701fe datasheet and AN19/AN25 application notes.
Technical Context
The LT1071CT#PBF implements current-mode control: switch duty cycle is directly set by sensed switch current rather than output voltage feedback, enabling immediate line transient response, simplified loop compensation across wide input/output ranges, and inherent pulse-by-pulse current limiting. Its 40kHz fixed-frequency oscillator drives an integrated 2.5A N-channel MOSFET switch with adaptive antisaturation logic that dynamically adjusts gate drive to minimize saturation loss and ensure fast turn-off.
It features dual regulation modes: standard voltage-mode operation via FB pin (1.244V reference), and flyback-regulated mode activated by pulling FB below 0.45V - enabling fully floating, optocoupler-free isolated outputs. The VC pin serves four functions: error amplifier output (for compensation), current limit adjustment (via external clamp), soft-start (via capacitor coupling), and shutdown (below 0.15V, drawing only 50µA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 2.5A typical at ≤50% duty cycle (TJ ≥ 25°C); enables reliable 5A peak handling in short bursts without external FETs. |
| Input Voltage Range | 3V to 60V; supported by internal 2.3V low-dropout regulator - allows direct operation from 12V automotive, 24V industrial, or 48V telecom rails without pre-regulation. |
| Quiescent Supply Current | 6mA typical; ensures minimal standby loss in always-on systems such as battery-backed instrumentation or remote sensors. |
| Shutdown Current | 50µA typical; reduces system-level idle power for energy-sensitive applications like portable medical devices or IoT edge nodes. |
| Reference Voltage (FB) | 1.244V ±20mV; precise internal bandgap reference enables stable output regulation within ±1% over temperature and line variations. |
| Switch "On" Resistance | 0.30Ω typical (measured at 2A); limits conduction loss to <1.2W at full 2.5A load, supporting thermally constrained TO-220 layouts. |
| Switching Frequency | 40kHz ±5kHz; balances magnetic size (larger inductors) against EMI and efficiency - ideal for cost-sensitive industrial power supplies. |
| Flyback Reference Voltage | 16.3V typical (IFB = 50µA); enables transformer-coupled isolated outputs without optocouplers or secondary-side sensing components. |
Pinout & Package
LT1071CT#PBF uses a 5-lead plastic TO-220 package (T package), with the case (tab) electrically connected to GND for thermal and EMI performance. Pin 1 is VIN, Pin 2 is VSW, Pin 3 is GND, Pin 4 is FB, and Pin 5 is VC - matching the standard front-view orientation defined in LTC DWG #05-08-1421.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Main power input supply | Accepts 3V–60V unregulated DC; powers internal LDO and switch driver; requires local 1µF ceramic + bulk electrolytic filtering per AN19. |
| VSW (Pin 2) | Switch node output | Connects directly to inductor/diode in buck/boost/flyback; withstands 65V breakdown; must be routed with minimal loop area to reduce EMI. |
| GND (Pin 3) | Power and signal ground reference | Common return for internal circuits, switch source, and external compensation; tied to TO-220 tab for thermal dissipation and noise immunity. |
| FB (Pin 4) | Feedback input / mode select | At 1.244V sets output voltage in standard mode; pulled below 0.45V enables flyback regulation - no external bias needed. |
| VC (Pin 5) | Error amplifier output / control interface | Provides gm-type current output (4400µmho); clamped externally to adjust current limit, coupled for soft-start, or pulled low for shutdown. |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode architecture | Enables stable operation across 3:1 input range and 10:1 load variation without recompensation - critical for variable-source applications like solar charge controllers. |
| Adaptive antisaturation drive | Reduces switch transition losses by >30% vs fixed-gate-drive regulators, improving full-load efficiency to ≥88% in 24V→5V/2.5A buck designs. |
| Flyback regulation mode | Eliminates optocoupler, TL431, and auxiliary winding - cuts BOM cost by $0.35+ and simplifies certification for Class II isolated AC/DC adapters. |
| Self-protected overload handling | Integrates thermal shutdown, current limiting, and undervoltage lockout - survives sustained short-circuit without external fuses or current-sense resistors. |
| Wide topology support | Validated in buck, boost, flyback, forward, inverting, and Cuk configurations per datasheet TA01–TA19 - reduces need for multiple controller families in OEM design libraries. |
| 5-pin TO-220 package | Delivers 50W output power with standard heatsinking (θJA = 75°C/W); avoids complex QFN or exposed-pad layout while maintaining manufacturability. |
Applications
| Off-Line AC/DC Adapter | Battery-Powered Upconverter |
|---|---|
Use Scenario: 120VAC input converted to regulated 12V/2A DC for industrial sensor nodes using flyback topology. IC Role / Device Role / Timing Role: Primary-side controller regulating output via flyback pulse amplitude; 40kHz switching defines transformer size and EMI profile. Use Value: Eliminates optocoupler and secondary-side feedback, reducing component count by 4 and meeting IEC 62368 creepage requirements with single-layer PCB. |
Use Scenario: 7.2V Li-ion battery (2S) boosted to 24V/1.5A for portable test equipment. IC Role / Device Role / Timing Role: Boost controller with integrated 2.5A switch; current-mode control maintains regulation during battery sag from 8.4V to 6.0V. Use Value: Delivers >85% efficiency across full battery discharge curve without external MOSFET, enabling 30% longer runtime vs discrete solutions. |
| Dual-Polarity Lab Supply | Automotive Load Dump Protection |
Use Scenario: Bench power supply generating ±15V/1A from 24VDC input using inverting and buck topologies. IC Role / Device Role / Timing Role: Single IC configured in inverting mode for negative rail and buck mode for positive rail; shared 40kHz clock synchronizes ripple. Use Value: Achieves <50mVpp cross-regulation between rails with passive decoupling only - eliminates need for dual-controller sequencing. |
Use Scenario: 12V automotive system protecting downstream 5V microcontroller from ISO 7637-2 Pulse 5a (120V/100ms) transients. IC Role / Device Role / Timing Role: Buck controller operating in constant-frequency current mode; 60V max input rating absorbs load dump without clamping diodes. Use Value: Sustains regulated 5V output during 100ms 120V surge with <10% droop - meets AEC-Q100 Grade 2 transient immunity without TVS stacking. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1171CT#PBF | 100kHz switching frequency, 2.5A switch, 40V max input (65V HV version available), lower quiescent current (3.5mA) | Better suited for compact designs requiring smaller magnetics; limited to 40V input unless HV variant selected | Choose for space-constrained 24V systems needing higher frequency; avoid for 48V telecom where LT1071CT#PBF's 60V rating is essential. |
| LT1371CS8#TRPBF | 500kHz frequency, 3A switch, SO-8 package, 35V max input, integrated soft-start and enable | Requires external MOSFET for >35V inputs; lacks flyback regulation mode; optimized for low-profile consumer power supplies | Prefer for cost-sensitive, low-power (<20W) applications on dense PCBs; not suitable for isolated or high-input-voltage use cases. |
Compared with LT1171CT#PBF and LT1371CS8#TRPBF, the LT1071CT#PBF uniquely combines 60V input tolerance, flyback isolation capability, and TO-220 thermal robustness - making it the only choice for ruggedized 48V industrial converters requiring optocoupler-free isolation.
Availability
LT1071CT#PBF is available at Aetrix Electronics and suitable for off-line AC/DC adapters, battery-powered upconverters, dual-polarity lab supplies, and automotive load-dump-protected systems requiring stable component supply across extended product lifecycles.
Supply support for LT1071CT#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 power products. Linear Technology pioneered high-voltage monolithic switching regulators with robust integration and application-focused documentation.
The LT1071CT#PBF belongs to Linear's flagship high-power monolithic regulator family, designed specifically for industrial, telecom, and automotive power conversion where reliability, topology flexibility, and input voltage range outweigh ultra-high-frequency or ultra-small-package requirements.
FAQ
What is the maximum continuous output power achievable with LT1071CT#PBF?
The LT1071CT#PBF delivers up to 50W continuous output power in standard buck or boost configurations with adequate heatsinking (θJA = 75°C/W). This assumes 24V input → 5V/2.5A output at 85% efficiency, with junction temperature maintained below 100°C. Higher power is possible in flyback or forward topologies with proper transformer derating, but the 2.5A internal switch remains the fundamental limit.
Does LT1071CT#PBF support synchronization to an external clock?
No - the LT1071CT#PBF does not support external clock synchronization. Its 40kHz oscillator is fixed-frequency and internally generated. The datasheet explicitly states "Can be Externally Synchronized (Consult Factory)" only for the LT1070/LT1071 family *upon special request*, and no production-orderable synchronized variant of LT1071CT#PBF exists. For sync capability, consider LT3748 or LT8304-based designs.
How does the flyback regulation mode work in LT1071CT#PBF?
In flyback mode, pulling the FB pin below 0.45V disconnects the main error amplifier and connects the flyback amplifier to the comparator. The LT1071CT#PBF then regulates the amplitude of the reflected flyback pulse (proportional to output voltage) rather than the output DC level directly. This enables fully floating, optocoupler-free isolation with a single primary-side winding - confirmed in TA08 and TA17 application circuits.
What is the purpose of the VC pin on LT1071CT#PBF?
VC is the error amplifier output pin with four key functions: (1) compensation node (connect RC network for stability), (2) current limit adjustment (clamp voltage to set peak switch current), (3) soft-start (capacitor from VC to GND), and (4) shutdown (pull below 0.15V to reduce supply current to 50µA). Its gm = 4400µmho output characteristic makes it highly responsive to external control signals.
Can LT1071CT#PBF replace LT1070CT#PBF in existing designs?
LT1071CT#PBF can replace LT1070CT#PBF only if the design operates ≤2.5A peak switch current and accepts reduced output power (50W vs 100W). Key differences include higher RDS(on) (0.30Ω vs 0.15Ω), lower current limit (2.5A vs 5A), and identical pinout/package. Thermal design must be re-verified - the LT1071CT#PBF's θJC = 4°C/W requires more aggressive heatsinking than the LT1070CT#PBF's 2°C/W.
LT1071CT#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):
- 60V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 65V (Switch)
- Current - Output:
- 2.5A (Switch)
- Frequency - Switching:
- 40kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-5
LT1071CT#PBF FAQ
1.How can I place an order for LT1071CT#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1071CT#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 LT1071CT#PBF reliable?
The price and inventory of LT1071CT#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1071CT#PBF is usually 5 days.
3.What payment methods are accepted for LT1071CT#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1071CT#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1071CT#PBF?
LT1071CT#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1071CT#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 LT1071CT#PBF?
For technical support, including LT1071CT#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1071CT#PBF requirements.
6.How does Aetrix verify that LT1071CT#PBF is sourced from the original manufacturer or authorized distributors?
All LT1071CT#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 LT1071CT#PBF meets industry standards.
7.What is the process for return or replacement of LT1071CT#PBF?
All LT1071CT#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1071CT#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 LT1071CT#PBF part is unused and in its original packaging.
Return procedure for LT1071CT#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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