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Analog Devices Inc. LT3491EDC#PBF
- Part No.:
- LT3491EDC#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 6-WFDFN Exposed Pad
- Datasheet:
-
LT3491EDC#PBF.pdf
- Description:
- IC LED DRIVER WHITE BCKLGT
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT3491EDC#PBF from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode boost DC/DC converter IC designed to drive up to six white LEDs in series from a 2.5V–12V input, featuring integrated Schottky diode, high-side current sensing, and single-pin PWM dimming/shutdown control. It delivers ±5% reference accuracy, 2.3MHz switching, and 27V open-LED protection in a 6-lead 2mm × 2mm DFN package.
For engineers reviewing the LT3491EDC#PBF datasheet, LT3491EDC#PBF pinout, LT3491EDC#PBF application, or LT3491EDC#PBF equivalent, key selection criteria include LED string count support (up to 6), 200mV current-sense voltage tolerance, 27V overvoltage clamp, SC70/DFN package thermal performance, and compatibility with Li-Ion, alkaline, or 3.3V logic-supplied systems.
Technical Context
The LT3491EDC#PBF employs constant-frequency current-mode control with internal ramp compensation for stable regulation across line and load variations. Its high-side sense architecture enables "one-wire" LED string connection by referencing current sense to the LED anode rather than ground, eliminating ballast resistors and simplifying PCB routing.
It integrates a 27V-capable Schottky diode, 2.3MHz oscillator, and precision 200mV current-sense reference with ±5% accuracy over temperature. The CTRL pin simultaneously controls shutdown (≤50mV) and analog/PWM dimming (0–1.5V), supporting true-color PWM dimming up to 300:1 range without chromatic shift.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.5V to 12V - supports single-cell Li-Ion (2.7–4.2V), dual-AA (2–3.2V), or regulated 3.3V/5V supplies without external LDO. |
| LED String Capacity | Up to 6 white LEDs - enables uniform brightness via series connection; output voltage capability up to 32V ensures headroom for VF variation and temperature drift. |
| Current Sense Voltage | 200mV ±5% - sets LED current as ILED = 200mV/RSENSE; low value minimizes power loss and heat in sense resistor. |
| Switching Frequency | 2.3MHz (1.8–2.8MHz typ) - allows use of tiny 10µH inductors and 1µF ceramic capacitors, reducing board area and EMI filter complexity. |
| Open-LED Protection | 27V clamp (26–28V typ) - prevents destructive overvoltage during LED string disconnection or failure; reduces input current to <10µA in fault condition. |
| Package | 6-lead DFN (2mm × 2mm × 0.75mm) - exposed pad improves thermal resistance (θJA = 102°C/W); compatible with standard reflow and space-constrained portable layouts. |
| Dimming Range | 300:1 true-color PWM - maintains LED chromaticity by avoiding analog current modulation; supports direct PWM dimming ≥80Hz to eliminate visible flicker. |
Pinout & Package
LT3491EDC#PBF uses the 6-lead DFN package (2mm × 2mm × 0.75mm) with exposed thermal pad (Pin 7) requiring solder connection to PCB ground for rated thermal performance. Pin 1 is marked by chamfered corner; top marking is "LCHJ".
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 1) | Power Switch Drain | Connects to inductor; high dv/dt node-must minimize trace area to reduce EMI radiation and parasitic coupling. |
| GND (Pin 2) | Ground Reference | Primary ground return for control circuitry; must tie directly to local ground plane, not shared with power GND traces. |
| CTRL (Pin 3) | Dimming & Shutdown Input | Analog/PWM control pin: ≤50mV = shutdown; 0–1.5V = linear LED current scaling; >1.5V = full current; bias current <100nA. |
| LED (Pin 4) | LED Anode Sense Node | High-side current sense point-connects to first LED anode and RSENSE top; referenced to CAP for 200mV differential measurement. |
| CAP (Pin 5) | Boost Output / Schottky Cathode | Regulated output node; connects to cathode of internal Schottky and output capacitor; clamped at 27V during open-circuit faults. |
| VIN (Pin 6) | Input Supply | 2.5–12V input; requires local 1µF ceramic bypass capacitor placed adjacent to pin to suppress high-frequency noise and supply ripple. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky Diode | Enables self-contained boost topology-no external diode required; rated for 1A inrush and 100mA continuous forward current with 0.8V drop at 100mA. |
| High-Side Current Sensing | Eliminates need for ground-referenced sense resistor-allows LED cathodes to be grounded anywhere, simplifying mechanical layout and enabling flexible display mounting. |
| Single-Pin Dimming/Shut Down | Reduces system BOM and routing complexity-CTRL pin accepts DC voltage, filtered PWM, or direct PWM signals without external components for basic operation. |
| 27V Open-LED Clamp | Prevents damage during LED string failure or connector disconnect-limits CAP voltage to safe level while reducing quiescent current to <10µA in fault state. |
| 2.3MHz Fixed-Frequency Operation | Permits use of miniature passive components-10µH inductor and 1µF ceramic caps meet most designs, cutting solution size vs. lower-frequency alternatives. |
Applications
| Cellular Phone Backlight | Digital Camera Flash |
|---|---|
|
Use Scenario: Driving 4-series white LEDs for main LCD backlight in GSM/UMTS handsets powered by single Li-Ion cell (3.0–4.2V). IC Role / Device Role / Timing Role: Boost converter with integrated Schottky and high-side sensing-provides regulated current source independent of battery voltage sag. Use Value: Maintains consistent display brightness across battery discharge cycle; 2.3MHz switching avoids audible noise in speaker-sensitive RF sections. |
Use Scenario: Delivering 200mA pulsed current to 1–2 white LEDs for camera flash in compact handheld devices. IC Role / Device Role / Timing Role: High-efficiency boost driver with fast transient response-enables precise flash duration control via PWM dimming at ≥1kHz. Use Value: Achieves >75% efficiency at 200mA flash load; 27V open-LED protection prevents latch-up if flash LED fails open during burst mode. |
| GPS Receiver Display | MP3 Player UI Lighting |
|
Use Scenario: Powering 3-white-LED string for outdoor-readable GPS display under variable lighting conditions. IC Role / Device Role / Timing Role: Constant-current LED driver with wide dimming range-supports analog + PWM hybrid dimming down to <20µA average current. Use Value: Enables seamless transition from daylight-bright (20mA) to night-vision-safe (0.02mA) modes without color shift or visible flicker. |
Use Scenario: Illuminating OLED or segment LCD UI in battery-powered MP3 players using dual-AA cells (2–3.2V). IC Role / Device Role / Timing Role: Low-input-voltage boost controller-VIN supplied from 3.3V logic rail while inductor driven from battery, maximizing overall system efficiency. Use Value: Extends playback time by >15% vs. conventional boost architectures; 6-lead DFN fits tight bezel space behind small displays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar white LED boost driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3465EDD#PBF | 2.7MHz switching, same 200mV sense, but higher 16V max VIN and no integrated Schottky-requires external diode. | Better suited for 5–16V industrial inputs; less compact due to external diode and larger 8-lead DFN footprint. | Select when higher input voltage range or tighter EMI control (via adjustable frequency) is prioritized over component count reduction. |
| LT1937ES5#TRPBF | 1.2MHz operation, 2.5–10V VIN, integrated Schottky, but limited to 4-LED strings and 34V max VOUT. | Optimized for ultra-low-power portable devices; lower switching frequency increases inductor size and may cause audible noise. | Choose for cost-sensitive designs where 4-LED limit is acceptable and 2.3MHz EMI sensitivity is a concern. |
Compared with LT3491EDC#PBF, LT3465EDD#PBF trades integrated diode simplicity for wider input range and higher frequency, while LT1937ES5#TRPBF offers lower quiescent current but sacrifices LED count scalability and switching speed-making LT3491EDC#PBF optimal for 5–6 LED, space-constrained, Li-Ion-powered applications demanding minimal external parts.
Availability
LT3491EDC#PBF is available at Aetrix Electronics and suitable for cellular phones, digital cameras, GPS receivers, and MP3 players requiring stable component supply, long-lifecycle availability, and RoHS-compliant packaging.
Supply support for LT3491EDC#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 its legacy of high-performance analog ICs for power management, signal conditioning, and precision timing.
The LT3491EDC#PBF belongs to Linear's white LED driver product line, engineered specifically for portable consumer electronics requiring high integration, small footprint, and robust fault protection in battery-constrained environments.
FAQ
What is the maximum number of white LEDs the LT3491EDC#PBF can drive?
The LT3491EDC#PBF is specified to drive up to six white LEDs in series from a 2.5V–12V input. This is enabled by its 32V LED pin rating and internal 27V open-LED clamp, ensuring safe operation even with worst-case forward voltage (VF) spread across the string. For six typical 3.2V white LEDs, total VF ≈ 19.2V, leaving ample margin for regulation and temperature drift. The LT3491EDC#PBF achieves this with only one external inductor and capacitor.
Does the LT3491EDC#PBF require an external Schottky diode?
No, the LT3491EDC#PBF integrates a Schottky diode rated for 100mA continuous forward current and 1A peak inrush. This eliminates the need for an external diode, reducing BOM count, PCB area, and assembly cost. The internal diode has a typical forward drop of 0.8V at 100mA and leakage <4µA at 20V reverse bias-verified in the Electrical Characteristics table of the LT3491EDC#PBF datasheet.
How does the high-side current sensing in the LT3491EDC#PBF simplify design?
The LT3491EDC#PBF senses LED current on the high side (between CAP and LED pins), allowing the LED cathodes to connect directly to system ground-eliminating the need for a separate ground-return path for the sense resistor. This "one-wire" LED connection simplifies mechanical layout, avoids ground loop issues in multi-display systems, and enables flexible placement of LED arrays relative to the PCB ground plane. The LT3491EDC#PBF achieves this without sacrificing accuracy, maintaining ±5% sense voltage tolerance.
What dimming methods does the LT3491EDC#PBF support?
The LT3491EDC#PBF supports three dimming methods via its CTRL pin: (1) analog DC voltage (0–1.5V), (2) filtered PWM signal (RC-filtered to DC-equivalent), and (3) direct PWM switching (≥80Hz). All methods deliver true-color dimming up to 300:1 range without shifting LED chromaticity. Direct PWM is preferred for highest fidelity; the LT3491EDC#PBF's fast settling time (~30µs) enables >1kHz PWM frequencies with minimal duty-cycle limitation.
What thermal considerations apply to the LT3491EDC#PBF in DFN package?
The LT3491EDC#PBF in 6-lead DFN (2mm × 2mm) relies on its exposed thermal pad (Pin 7) soldered to PCB ground for effective heat dissipation. With θJA = 102°C/W, it requires a minimum 100mm² copper pour under the pad to maintain junction temperature below 125°C at full load. Layout guidelines mandate short, wide traces to SW and VIN, separation of CAP/LED sense nodes from noisy switching paths, and placement of COUT adjacent to the CAP pin-all critical to thermal and electrical performance of the LT3491EDC#PBF.
LT3491EDC#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 6-WFDFN Exposed Pad
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- -
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- -
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 2.5V
- Voltage - Supply (Max):
- 12V
- Voltage - Output:
- -
- Current - Output / Channel:
- -
- Frequency:
- 1.8MHz ~ 2.8MHz
- Dimming:
- -
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 6-DFN (2x2)
LT3491EDC#PBF FAQ
1.How can I place an order for LT3491EDC#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3491EDC#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 LT3491EDC#PBF reliable?
The price and inventory of LT3491EDC#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3491EDC#PBF is usually 5 days.
3.What payment methods are accepted for LT3491EDC#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3491EDC#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3491EDC#PBF?
LT3491EDC#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3491EDC#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 LT3491EDC#PBF?
For technical support, including LT3491EDC#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3491EDC#PBF requirements.
6.How does Aetrix verify that LT3491EDC#PBF is sourced from the original manufacturer or authorized distributors?
All LT3491EDC#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 LT3491EDC#PBF meets industry standards.
7.What is the process for return or replacement of LT3491EDC#PBF?
All LT3491EDC#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3491EDC#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 LT3491EDC#PBF part is unused and in its original packaging.
Return procedure for LT3491EDC#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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