My Inquiry
My Account
Analog Devices Inc. LT1271CQ#PBF
- Part No.:
- LT1271CQ#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Datasheet:
-
LT1271CQ#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 4A DDPAK-5
- Quantity:
- Payment:
- Shipping:
Inventory:337
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT1271CQ#PBF from Analog Devices (formerly Linear Technology) is a monolithic 4A, 60kHz switching regulator IC in a 5-lead DD Pak package, featuring an integrated high-current switch, current-mode control, and flyback-capable feedback architecture. It operates from 3.5V to 30V input, delivers up to 3A output in buck mode, supports boost/buck-boost/flyback topologies, and is used in PC power supplies with multiple outputs and battery up-converters.
For engineers reviewing the LT1271CQ#PBF datasheet, LT1271CQ#PBF pinout, LT1271CQ#PBF application, or LT1271CQ#PBF equivalent, key selection criteria include its 4A internal switch rating, 60kHz fixed switching frequency, 7mA quiescent current, shutdown mode drawing only 100µA, and compatibility with standard 5-pin TO-220–form-factor layouts using the DD Pak thermal design.
Technical Context
The LT1271CQ#PBF implements current-mode PWM control with adaptive anti-saturation switch drive for wide load-current efficiency stability. Its error amplifier features 1.244V reference voltage (±20mV tolerance), 4400 µmho transconductance, and clamped output (0.25–2.3V) to ensure robust loop response across line and load transients.
It supports external synchronization via the VC pin, enables burst-mode operation for light-load efficiency, and includes self-protection against overloads through cycle-by-cycle current limiting (4A typical at 50% duty cycle) and thermal shutdown at 125°C junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 60kHz fixed - determines inductor size, EMI profile, and minimum on-time constraints for stable operation. |
| Internal Switch Current | 4A typical - eliminates need for external MOSFET in medium-power DC/DC designs up to ~30W. |
| Input Voltage Range | 3.5V to 30V - supports 5V, 12V, and 24V industrial/bus rails without pre-regulation. |
| Quiescent Current | 7mA - enables low-noise, high-efficiency operation in always-on systems without excessive standby loss. |
| Shutdown Current | 100µA typical - allows deep sleep states in battery-powered applications while retaining fast wake-up capability. |
| Reference Voltage | 1.244V ±20mV - sets output voltage accuracy in feedback loop; enables precise 3.3V, 5V, or adjustable regulation. |
| Max Duty Cycle | 92% - supports high step-down ratios (e.g., 24V → 3.3V) without requiring external diode clamp or complex compensation. |
Pinout & Package
The LT1271CQ#PBF is housed in a 5-lead plastic DD Pak (Q package), featuring exposed copper thermal pad on bottom for direct PCB heat sinking. θJA = 30°C/W with 1 oz copper ground plane, enabling >3A continuous output without heatsink under moderate ambient conditions.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Power Input | Accepts 3.5V–30V unregulated supply; connects to input capacitor and ESD protection network. |
| VSW | Switch Output | Drives external inductor/diode in buck/boost/flyback; rated for 60V breakdown and 4A peak current. |
| GND | Power & Signal Ground | Common return for switch, feedback, and control circuits; must be low-impedance connection to thermal pad. |
| FB | Feedback Input | Senses output voltage divider; 1.244V reference sets regulation point; high-impedance (≤750nA bias). |
| VC | Control Voltage | Enables shutdown (≤0.5V), burst mode (open), or external sync (AC-coupled square wave). |
Key Features
| Feature | Design Value |
|---|---|
| Fully integrated 4A power switch | Reduces BOM count by eliminating external MOSFET and gate driver; simplifies layout and improves reliability. |
| Current-mode PWM control | Provides inherent cycle-by-cycle current limiting and excellent line/load transient response without slope compensation. |
| Flyback-regulated floating outputs | Enables isolated dual-output designs (e.g., ±12V) using single transformer without optocoupler feedback. |
| Adaptive anti-saturation drive | Maintains high efficiency (>85%) from 10% to 100% load across full input range without external tuning. |
| Standard 5-pin DD Pak footprint | Offers TO-220–compatible mechanical mounting and thermal performance in smaller surface-mount package. |
Applications
| PC Power Supply with Multiple Outputs | Battery Up-Converter |
|---|---|
Use Scenario: Generating +5V, +12V, and –12V rails from a 24V industrial bus in embedded computing systems. IC Role / Device Role / Timing Role: Primary controller in flyback configuration with multi-winding transformer, regulating all outputs via primary-side sensing. Use Value: Eliminates need for secondary-side regulators or optocouplers; achieves >90% efficiency at 1.5A per rail with single LT1271CQ#PBF. | Use Scenario: Boosting 7.2V Li-ion battery pack to 12V for portable instrumentation or motor drivers. IC Role / Device Role / Timing Role: High-efficiency boost converter core with internal 4A switch handling peak inductor currents up to 5A. Use Value: Delivers 12V@2A continuously from 7.2V input with <0.3V dropout margin and no external FET required. |
| Negative-to-Positive Buck-Boost Converter | High Efficiency Buck Converter |
Use Scenario: Converting –12V telecom supply to +5V logic rail in legacy telecom line cards. IC Role / Device Role / Timing Role: Inverting buck-boost topology controller; uses VSW as active switch node and FB for output voltage sensing. Use Value: Achieves regulated [email protected] with <1% line regulation and no polarity-reversal components beyond standard diode and inductor. | Use Scenario: Stepping down 24V factory automation bus to 3.3V for microcontroller and sensor subsystems. IC Role / Device Role / Timing Role: Synchronous-capable buck controller driving external high-side MOSFET (with optional external low-side rectification). Use Value: Supports 3.3V@3A output with 92% efficiency at full load and 7mA quiescent current during idle cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-current switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1374CS#PBF | 500kHz switching frequency, 4.5A switch, SO-8 package, VIN ≤25V | Better suited for compact, high-density designs requiring faster transient response and lower inductance | Select when board space is constrained and higher-frequency magnetics are acceptable |
| LT1269CQ#PBF | Same Q package, but 100kHz frequency and slightly lower 3.5A switch rating | Preferred for higher efficiency at light loads and tighter output ripple due to higher frequency | Select when optimizing for ripple-sensitive analog subsystems or higher switching efficiency below 1A load |
Compared with LT1271CQ#PBF, LT1374CS#PBF offers 8.3× higher frequency and smaller passive size but sacrifices input voltage headroom and thermal robustness in DD Pak; LT1269CQ#PBF trades 40kHz bandwidth for improved light-load efficiency and reduced EMI filtering burden, with identical pinout and layout compatibility.
Availability
LT1271CQ#PBF is available at Aetrix Electronics and suitable for PC power supplies with multiple outputs, battery up-converters, negative-to-positive converters, and high-efficiency buck converters requiring stable component supply across industrial and embedded production cycles.
Supply support for LT1271CQ#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 product support, datasheet archives, and application engineering for legacy Linear switching regulators.
The LT1271CQ#PBF belongs to Linear's monolithic high-power switching regulator family, designed for rugged, low-component-count DC/DC conversion in industrial, telecom, and computing power systems where reliability and thermal simplicity are critical.
FAQ
What is the maximum output current achievable with the LT1271CQ#PBF in buck configuration?
The LT1271CQ#PBF supports up to 3A continuous output current in buck mode, based on its 4A internal switch rating, thermal limits of the DD Pak package (θJA = 30°C/W), and typical efficiency of 90% at mid-load. Derating is required above 60°C ambient or with inadequate PCB copper area; full 3A assumes ≥1 sq. in. of 1 oz copper connected to the thermal pad.
Does the LT1271CQ#PBF require an external flyback transformer for isolated outputs?
Yes, the LT1271CQ#PBF requires an external flyback transformer to implement isolated outputs. Its flyback-regulated mode relies on transformer coupling and primary-side sensing via the FB pin; no optocoupler or secondary-side regulator is needed, but transformer turns ratio, leakage inductance, and saturation current must be carefully selected per AN-19 design guidelines.
Can the LT1271CQ#PBF be synchronized to an external clock signal?
Yes, the LT1271CQ#PBF can be externally synchronized using the VC pin. Applying a clean TTL- or CMOS-compatible square wave (≥1Vpp) to VC overrides the internal 60kHz oscillator. The device locks to the external frequency if it falls within ±20% of nominal, enabling EMI reduction and multi-rail phase alignment in complex power systems.
What is the purpose of the VC pin on the LT1271CQ#PBF besides synchronization?
Beyond synchronization, the VC pin on the LT1271CQ#PBF controls operating mode: ≤0.5V enables shutdown (100µA supply current), open circuit enables normal operation or burst mode (depending on load), and 0.8V–1.4V allows linear control of duty cycle for analog dimming or programmable output adjustment in custom feedback loops.
Is the LT1271CQ#PBF pin-compatible with the LT1269CQ#PBF?
Yes, the LT1271CQ#PBF is pin-compatible with the LT1269CQ#PBF - both use identical 5-lead DD Pak packaging, identical pinout (VIN/VSW/GND/FB/VC), and share the same thermal and layout requirements. The only functional differences are switching frequency (60kHz vs. 100kHz) and switch current rating (4A vs. 3.5A), making them direct drop-in alternatives for most designs.
LT1271CQ#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, 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:
- Surface Mount
- Supplier Device Package:
- DDPAK-5
LT1271CQ#PBF FAQ
1.How can I place an order for LT1271CQ#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1271CQ#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 LT1271CQ#PBF reliable?
The price and inventory of LT1271CQ#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1271CQ#PBF is usually 5 days.
3.What payment methods are accepted for LT1271CQ#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1271CQ#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1271CQ#PBF?
LT1271CQ#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1271CQ#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 LT1271CQ#PBF?
For technical support, including LT1271CQ#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1271CQ#PBF requirements.
6.How does Aetrix verify that LT1271CQ#PBF is sourced from the original manufacturer or authorized distributors?
All LT1271CQ#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 LT1271CQ#PBF meets industry standards.
7.What is the process for return or replacement of LT1271CQ#PBF?
All LT1271CQ#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1271CQ#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 LT1271CQ#PBF part is unused and in its original packaging.
Return procedure for LT1271CQ#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT1271CQ#PBF Tags
-
TPS562201DDCR
Texas Instruments
-
MC34063ABD-TR
STMicroelectronics
-
TPS561201DDCR
Texas Instruments
-
MC33063ADR
Texas Instruments
-
MC34063ADR
Texas Instruments
-
TPS560200DBVR
Texas Instruments
-
AP3012KTR-G1
Diodes Incorporated
-
TLV61048DBVR
Texas Instruments
-
AZ34063UMTR-G1
Diodes Incorporated
-
TPS562200DDCR
Texas Instruments
-
AP62300TWU-7
Diodes Incorporated
-
MC34063EBD-TR
STMicroelectronics
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
