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Analog Devices Inc. LT3479EDE
- Part No.:
- LT3479EDE
- Manufacturer:
- Analog Devices Inc.
- Package:
- 14-WFDFN Exposed Pad
- Datasheet:
-
LT3479EDE.pdf
- Description:
- IC REG BOOST ADJ 3A 14DFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,664
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Product details
Overview
LT3479EDE from Analog Devices (formerly Linear Technology) is a current-mode, fixed-frequency step-up DC/DC converter with an integrated 3A, 42V NPN switch, programmable 200kHz–3.5MHz switching frequency, soft-start, and inrush current protection. It supports both positive and negative output configurations and operates across 2.5V–24V input, delivering up to 89% efficiency in 5V-to-12V boost applications.
For engineers reviewing the LT3479EDE datasheet, LT3479EDE pinout, LT3479EDE application, or LT3479EDE equivalent, key selection considerations include its 14-pin 4mm × 3mm DFN package with exposed power ground pad, dual feedback amplifier inputs (FBP/FBN), RT-programmable oscillator, and robust 5A inrush current protection threshold - all critical for high-reliability LED drivers and distributed power systems.
Technical Context
The LT3479EDE employs fixed-frequency current-mode control with slope compensation, using an internal 8.5mΩ sense resistor for inductor current monitoring and a dedicated inrush protection comparator that triggers soft-start upon >5A transient detection. Its error amplifier features fully accessible FBP (non-inverting) and FBN (inverting) inputs, enabling flexible positive or negative output regulation via external resistive dividers.
Switching frequency is set by a single external resistor on the RT pin, with guaranteed operation from 200kHz to 3.5MHz; minimum input voltage is 2.5V, and maximum switch voltage is 42V. The device integrates a 1.235V bandgap reference (VREF), soft-start capacitor interface (SS), and compensation node (VC) for type-II/III loop stabilization.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 24V - supports wide-range industrial and battery-powered inputs including Li-ion (2.8V–4.2V) and 5V/12V rails. |
| Switch Rating | 3A continuous, 42V max - enables high-current boost conversion without external MOSFETs in sub-12W designs. |
| Switching Frequency | 200kHz to 3.5MHz (RT-programmable) - allows trade-off between EMI filtering size and efficiency; 1MHz typical for compact 5V→12V/800mA designs. |
| Reference Voltage | 1.235V ±19mV - precise internal bandgap used directly for feedback; stable over –40°C to 85°C. |
| Soft-Start Control | 10μA constant-current source into SS pin - enables controlled ramp of VC voltage to limit peak inductor current at startup. |
| Inrush Protection Threshold | 5A inductor current - internal comparator initiates new soft-start cycle during shorts or hot-plug transients, preventing switch overstress. |
| Efficiency | Up to 89% - achieved in 5V-to-12V/800mA 1MHz boost configuration with Schottky diode and low-DCR inductor. |
Pinout & Package
LT3479EDE is housed in a thermally enhanced 14-lead plastic DFN package (4mm × 3mm, 0.75mm height) with exposed power ground pad (Pin 15) requiring PCB soldering for thermal and electrical integrity. θJA = 43°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pins 1, 2) | Switch Collector | High-side NPN collector node; connects to inductor and flyback diode - minimize trace area to reduce EMI. |
| L (Pin 3) | Inductor Connection | Direct tie point for inductor; forms current-sense path with internal 8.5mΩ resistor for inrush protection. |
| VS (Pin 4) | Inductor Supply Rail | Powers switch driver and inductor bias; must be locally bypassed; can be tied to VIN if single supply is used. |
| VIN (Pin 5) | Control Circuit Supply | Powers internal logic, reference, and error amplifier; requires local ceramic bypass capacitor. |
| RT (Pin 6) | Oscillator Timing Input | Connects to external resistor to set switching frequency; open-circuit prohibited. |
| SHDN (Pin 7) | Enable/Disable Control | Active-high shutdown: <0.3V disables, ≥1.5V enables; draws ≤60μA when active. |
| VREF (Pin 8) | Bandgap Reference Output | 1.235V reference; supplies up to 100μA; bypass with 100pF for noise immunity. |
| FBP (Pin 9) | Error Amp Non-Inverting Input | Used for negative-output configurations - connect to divider tap referenced to –VOUT. |
| FBN (Pin 10) | Error Amp Inverting Input | Used for positive-output configurations - connect to divider tap referenced to VOUT. |
| VC (Pin 11) | Compensation Node | Output of error amplifier; connect series RC (e.g., 10kΩ + 2.2nF) to GND for loop stability. |
| SS (Pin 12) | Soft-Start Capacitor Terminal | 10μA current source charges external capacitor to control VC ramp rate and limit startup current. |
| GND (Pins 13, 14) | Analog Ground | Return for control circuitry; separate from PGND (exposed pad) to minimize noise coupling. |
| Exposed Pad (Pin 15) | Power Ground (PGND) | Mandatory solder connection to PCB ground plane for thermal dissipation and low-impedance switch return path. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable Switching Frequency | 200kHz–3.5MHz via single RT resistor - enables optimization of magnetics size, EMI, and efficiency without changing IC. |
| Dual Feedback Inputs (FBP/FBN) | Full access to error amplifier inputs - supports both positive and negative output topologies without external op-amps. |
| Inrush Current Protection | Automatic soft-start re-initiation at >5A inductor current - protects switch and external components during short circuits or hot-plug events. |
| Low VCE(SAT) | 200mV typical at 1A - reduces conduction loss and improves efficiency in high-current boost stages. |
| Thermally Enhanced DFN | 4mm × 3mm footprint with exposed PGND pad - delivers 43°C/W θJA, enabling 3A operation without heatsink in compact layouts. |
Applications
| High-Power LED Driver | DSL Modem Power Supply |
|---|---|
Use Scenario: Driving 12 white LEDs (3.3V each) from a 3.3V–4.2V Li-ion battery in photo-flash or backlight applications. IC Role / Device Role / Timing Role: Step-up regulator providing constant-current LED drive with adjustable torch/flash modes and output disconnect. Use Value: Integrated 3A switch and inrush protection eliminate need for external MOSFET and fault-handling circuitry, reducing BOM count and board area. |
Use Scenario: Generating +12V and –12V rails from a 5V input in DSL line card power management. IC Role / Device Role / Timing Role: Dual-output inverting/boost converter supplying isolated analog front-end and line driver circuitry. Use Value: Single-chip solution replaces two discrete regulators; FBP/FBN flexibility enables precise –12V regulation without additional amplifiers. |
| Distributed Power System | TFT-LCD Panel Supply |
Use Scenario: Local 5V-to-12V boost conversion at point-of-load in industrial PLC I/O modules with strict EMI limits. IC Role / Device Role / Timing Role: High-efficiency, RT-programmable DC/DC converter operating at 1.5MHz to shrink filter components. Use Value: 89% peak efficiency and 43°C/W thermal resistance allow full 3A load in space-constrained enclosures without forced air cooling. |
Use Scenario: Triple-output (8V, 16V, –8V) power supply for TFT-LCD gate/source drivers requiring tight cross-regulation. IC Role / Device Role / Timing Role: Primary boost controller generating main rail, with auxiliary windings feeding linear post-regulators. Use Value: Programmable soft-start and inrush protection prevent display flicker or latch-up during cold start and hot-swap events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar boost converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3436 | 3A switch, 34V max, TSSOP-16 package, 3V–25V input, no inrush protection | Higher input voltage ceiling but lacks integrated inrush current protection and dual feedback inputs | Choose LTC3436 for >24V input or where TSSOP thermal profile is preferred; use LT3479EDE when inrush robustness and negative output capability are required. |
| LT3466 | 2MHz, dual-channel, integrated Schottky, 2.7V–24V input, 40V max, optimized for white LED strings | Designed specifically for LED current regulation; lacks general-purpose FBP/FBN flexibility and inrush protection | Choose LT3466 for dedicated multi-string LED driving; select LT3479EDE for programmable general-purpose boost with wider topology support. |
Compared with LTC3436 and LT3466, the LT3479EDE uniquely combines 5A inrush protection, dual feedback inputs for bipolar outputs, and DFN thermal performance - making it optimal for ruggedized, multi-rail industrial and display power designs where fault resilience and layout compactness are critical.
Availability
LT3479EDE is available at Aetrix Electronics and suitable for high-power LED drivers, DSL modem power supplies, and distributed power systems requiring stable component supply, long-term lifecycle support, and consistent parametric performance across temperature.
Supply support for LT3479EDE 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, documentation, and manufacturing continuity for legacy Linear parts including the LT3479 family.
The LT3479 product line was designed for high-current, wide-input-voltage boost conversion in space-constrained applications such as portable instrumentation, telecom line cards, and display power - emphasizing thermal efficiency, fault resilience, and topology flexibility.
FAQ
What is the maximum output current achievable with the LT3479EDE in a 5V-to-12V boost configuration?
The LT3479EDE supports up to 3A switch current, but practical output current depends on duty cycle, efficiency, and thermal design. In a typical 5V-to-12V/1MHz boost application with proper layout and thermal management, the LT3479EDE reliably delivers 800mA at 12V (9.6W), as validated in the datasheet's TA03 schematic and efficiency curves.
Can the LT3479EDE generate a negative output voltage, and how is it configured?
Yes, the LT3479EDE can generate negative outputs using its fully accessible FBP and FBN pins. To configure a negative rail, connect VREF to FBP and place a resistive divider from –VOUT to GND, tapping FBN to the divider junction. The output magnitude is set by VOUT = –1.235 × (R3/R4), as shown in Figure 3 of the LT3479 datasheet.
What is the purpose of the exposed pad (Pin 15) on the LT3479EDE DFN package?
The exposed pad (Pin 15) on the LT3479EDE is designated as power ground (PGND) and must be soldered to the PCB ground plane. It serves dual roles: lowering thermal resistance (θJA = 43°C/W) for reliable 3A operation and providing a low-impedance return path for the high-current switch node, minimizing noise coupling into sensitive analog circuitry.
How does the inrush current protection function differ from standard current limiting in the LT3479EDE?
The LT3479EDE implements dedicated inrush current protection separate from its 3A switch current limit. When inductor current exceeds 5A - indicating a short or hot-plug transient - an independent comparator forces a new soft-start cycle, ramping VC from zero. This prevents destructive peak currents during faults, whereas the 3A limit only clamps normal switching peaks.
Which external components are mandatory for basic LT3479EDE operation, and what are their critical parameters?
Mandatory components for LT3479EDE operation include: (1) an RT resistor (e.g., 17.8kΩ for 1MHz); (2) input/output ceramic capacitors (X5R/X7R, ≥2.2μF input, ≥10μF output); (3) power inductor (4.7μH–10μH, ≥3A saturation current); and (4) Schottky diode (≥40V reverse, ≥3A avg). Layout requires minimized SW-node traces and exposed-pad soldering.
LT3479EDE Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 14-WFDFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up
- Output Configuration:
- Positive or Negative
- Topology:
- Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.3V
- Voltage - Input (Max):
- 24V
- Voltage - Output (Min/Fixed):
- 1.235V
- Voltage - Output (Max):
- 42V (Switch)
- Current - Output:
- 3A (Switch)
- Frequency - Switching:
- 200kHz ~ 3.5MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-DFN (4x3)
LT3479EDE FAQ
1.How can I place an order for LT3479EDE through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3479EDE 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 LT3479EDE reliable?
The price and inventory of LT3479EDE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3479EDE is usually 5 days.
3.What payment methods are accepted for LT3479EDE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3479EDE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3479EDE?
LT3479EDE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3479EDE 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 LT3479EDE?
For technical support, including LT3479EDE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3479EDE requirements.
6.How does Aetrix verify that LT3479EDE is sourced from the original manufacturer or authorized distributors?
All LT3479EDE 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 LT3479EDE meets industry standards.
7.What is the process for return or replacement of LT3479EDE?
All LT3479EDE units undergo pre-shipment inspection (PSI). If there is an issue with LT3479EDE, 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 LT3479EDE part is unused and in its original packaging.
Return procedure for LT3479EDE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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