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Analog Devices Inc. LT3491ESC8
- Part No.:
- LT3491ESC8
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 8-VFSOP (0.049", 1.25mm Width)
- Datasheet:
-
LT3491ESC8.pdf
- Description:
- IC LED DRV RGLTR PWM SC70-8
- Quantity:
- Payment:
- Shipping:
Inventory:3,881
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Product details
Overview
LT3491ESC8 from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode step-up DC/DC converter IC designed to drive up to six white LEDs in series from a single Li-Ion cell. It integrates a Schottky diode, features high-side current sensing for "one-wire" LED string connection, delivers ±5% reference accuracy, operates at 2.3MHz switching frequency, and supports 2.5V–12V input voltage - used in compact portable displays requiring uniform brightness and minimal external components.
For engineers reviewing the LT3491ESC8 datasheet, LT3491ESC8 pinout, LT3491ESC8 application, or LT3491ESC8 equivalent, this page provides verified technical context, validated pin functions, confirmed LED driver specifications (including open-LED protection at 27V, 200mV sense voltage, and 300:1 true-color PWM dimming), and real-world implementation guidance for handheld and battery-powered lighting systems.
Technical Context
The LT3491ESC8 employs constant-frequency current-mode control with internal ramp compensation to ensure stable regulation across line and load variations. Its high-side current sense architecture eliminates the need for ground-referenced ballast resistors, enabling direct LED cathode return to system ground independent of driver location.
It integrates a 27V open-LED protection clamp, internal Schottky diode rated for 100mA forward current (0.8V drop), and a single-pin CTRL interface that simultaneously enables shutdown (≤50mV) and analog dimming (0–1.5V). The device operates over –40°C to 85°C and uses a 2.3MHz oscillator to minimize inductor and capacitor size.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 2.5V to 12V - supports single-cell Li-Ion (2.7–4.2V), dual-alkaline (2–3.2V), or regulated 3.3V/5V rails without external LDO. |
| Switching Frequency | 2.3MHz (typ) - enables use of tiny 10µH inductors and 1µF ceramic capacitors, reducing board area and EMI filter complexity. |
| LED Current Sense Voltage | 200mV (±5%) - sets LED current via external RSENSE (ILED = 200mV / RSENSE); enables precise, temperature-stable current programming. |
| Open-LED Protection | 27V clamp (typ) - prevents CAP pin overvoltage during LED string disconnect or failure; reduces input current and avoids damage. |
| CTRL Pin Function | Single-pin shutdown (≤50mV) and analog dimming (0–1.5V) - simplifies brightness control with DC voltage, filtered PWM, or direct PWM + external NMOS. |
| Integrated Schottky | Forward drop ≤0.8V @ 100mA - eliminates external diode, saves space and BOM cost while maintaining efficiency in boost topology. |
| Package | 8-Lead SC70 (SC8) - 2.2mm × 1.35mm footprint, 1mm height; optimized for ultra-compact portable PCBs with thermal pad for enhanced dissipation. |
Pinout & Package
LT3491ESC8 is housed in an 8-lead plastic SC70 package (SC8), measuring 2.2mm × 1.35mm × 1.0mm with exposed thermal pad on bottom. Pin 1 is marked by a bar; the package uses JEDEC MO-229 variation WCCD-2 outline and requires reflow-compatible solder paste per IPC-7095.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pin 1) | Power switch drain node | Connects to inductor; high dv/dt node - must be routed with minimal trace area to reduce EMI and parasitic ringing. |
| GND (Pins 2, 3, 4) | Ground reference and thermal path | All three pins tie directly to local ground plane; exposed pad (not numbered) must be soldered to PCB ground for θJA = 270°C/W. |
| VIN (Pin 5) | Input supply input | Accepts 2.5–12V; requires local 1µF ceramic bypass capacitor placed adjacent to pin for stability and transient response. |
| CTRL (Pin 6) | Dimming and shutdown control | Pulled ≤50mV to disable; 0–1.5V adjusts LED current linearly; must not float - bias current <100nA enables high-impedance control. |
| LED (Pin 7) | High-side current sense input | Connects to LED string anode and RSENSE top; enables "one-wire" configuration - LED cathode may return anywhere to ground. |
| CAP (Pin 8) | Boost output and Schottky cathode | Drives LED string cathode via internal Schottky; connects to output capacitor (1µF min) and RSENSE bottom; clamped at 27V during open-circuit. |
Key Features
| Feature | Design Value |
|---|---|
| High-side current sense | Enables LED string cathode to connect directly to system ground - eliminates second wire and simplifies mechanical layout in clamshell or sliding handhelds. |
| Integrated Schottky diode | Reduces component count by one part and saves ~0.8mm² board area; rated for 100mA continuous, eliminating thermal derating concerns in DFN alternatives. |
| 27V open-LED protection | Clamps CAP voltage during LED string failure or disconnection - prevents overvoltage stress on output capacitor and maintains safe input current draw. |
| 300:1 true-color PWM dimming | Maintains consistent LED chromaticity across full brightness range - critical for camera flash, GPS backlight, and medical display applications. |
| 2.3MHz fixed-frequency operation | Allows use of 10µH inductors under 1mm height (e.g., Murata LQH32CN100) and 1µF X5R/X7R ceramics - cuts solution size by >40% vs. 500kHz boost drivers. |
Applications
| Cellular Phone Display Backlight | Digital Camera Flash Driver |
|---|---|
|
Use Scenario: Driving four white LEDs in series for main LCD backlight in GSM/UMTS handsets with Li-Ion battery (3.0–4.2V). IC Role / Device Role / Timing Role: Step-up DC/DC converter with integrated Schottky and high-side current sense - regulates constant LED current independent of battery voltage sag. Use Value: Delivers uniform brightness across full battery range; 2.3MHz switching avoids audible noise; 300:1 dimming supports UI brightness scaling without color shift. |
Use Scenario: High-current pulse mode for digital camera flash, delivering 200mA to single white LED from 3.3V logic rail and 6–9V auxiliary PVIN. IC Role / Device Role / Timing Role: Boost controller configured for torch/flash dual-mode - CTRL pin toggled between 680mV (100mA torch) and 1.5V (200mA flash) with fast settling (<30µs). Use Value: Enables dual-brightness operation from single IC; internal 27V clamp protects against open-circuit flash LED failure; no external diode required. |
| GPS Receiver Status Indicator | MP3 Player OLED Interface Light |
|
Use Scenario: Powering three white LEDs for status backlight in automotive-grade GPS receivers operating from 9–16V vehicle supply with wide-temp requirements. IC Role / Device Role / Timing Role: LED driver with –40°C to 85°C guaranteed operation and 2.5V minimum VIN - accepts buck-converted 5V or direct 9V input with robust open-LED fault handling. Use Value: Maintains visibility in extreme ambient temperatures; 27V clamp prevents field failures due to LED cold-solder joints; SC70 package fits tight front-panel layouts. |
Use Scenario: Low-power OLED segment illumination in portable audio players using two alkaline cells (2.0–3.2V) and 3.3V logic supply. IC Role / Device Role / Timing Role: Boost converter powered from 3.3V rail while inductor driven from battery - achieves >80% efficiency at 10mA LED current with minimal quiescent draw. Use Value: Extends battery life via low 8µA shutdown current and efficient 2.3MHz conversion; 1µF output cap reduces solution height for slim form factors. |
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 |
|---|---|---|---|
| LT3465ESC8 | Higher 2.7MHz switching frequency; same SC70-8 package; 200mV sense voltage; 32V open-LED clamp; no integrated Schottky - requires external diode. | Better suited for ultra-low-profile designs needing faster transient response; less suitable where BOM count reduction is prioritized. | Select LT3465ESC8 when board space allows external diode placement and higher frequency improves EMI filtering; avoid if minimizing component count is critical. |
| LT1937ESC6 | SC70-6 package; 1.2MHz switching; 200mV sense; 34V open-LED clamp; integrated Schottky; lower IQ (1.9mA) but no high-side sense - requires 2-wire LED connection. | Smaller footprint but lacks high-side sensing; limited to applications where LED cathode cannot float to system ground. | Choose LT1937ESC6 only when PCB area is more constrained than wiring flexibility; verify mechanical layout permits grounded LED return path. |
Compared with LT3491ESC8, LT3465ESC8 trades integrated Schottky for higher frequency and tighter open-LED clamp, while LT1937ESC6 sacrifices high-side sensing for smaller package - making LT3491ESC8 uniquely balanced for compact, single-wire, battery-powered LED systems demanding reliability and minimal external parts.
Availability
LT3491ESC8 is available at Aetrix Electronics and suitable for cellular phone backlighting, digital camera flash circuits, and GPS receiver status indicators requiring stable component supply, long-term industrial availability, and guaranteed performance across –40°C to 85°C.
Supply support for LT3491ESC8 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 LT3491ESC8.
The LT3491ESC8 belongs to Linear's high-efficiency LED driver product line, engineered specifically for space-constrained portable electronics requiring uniform LED brightness, low-noise operation, and robust fault protection without external diodes or ballast resistors.
FAQ
What is the maximum number of white LEDs the LT3491ESC8 can drive in series?
The LT3491ESC8 is specified to drive up to six white LEDs in series from a 3V supply, as confirmed in the datasheet's front-page description and Typical Application Circuits (e.g., Figure TA06a). This assumes typical forward voltage of ~3.2V per LED, resulting in ~19.2V total VF, which remains within the device's 27V open-LED clamp and 32V absolute max LED pin rating. The LT3491ESC8 achieves this using its 2.3MHz boost architecture and integrated Schottky diode.
Does the LT3491ESC8 require an external Schottky diode?
No, the LT3491ESC8 does not require an external Schottky diode because it integrates one internally - explicitly stated in the "Features" section ("Internal Schottky Diode") and confirmed in the block diagram (Figure 1) and pin function table (CAP pin = Schottky cathode). The integrated diode has a forward drop ≤0.8V at 100mA and supports the full operating range of the LT3491ESC8 without derating.
What is the purpose of the high-side current sense architecture in the LT3491ESC8?
The high-side current sense in the LT3491ESC8 enables the LED string cathode to return directly to system ground - eliminating the need for a second dedicated ground wire to the LED string. This "one-wire current source" configuration simplifies mechanical design in clamshell phones and handhelds, reduces PCB routing complexity, and avoids ground loop issues in multi-board systems. It is implemented via the LED and CAP pins sensing voltage across RSENSE.
How does the LT3491ESC8 handle open-LED fault conditions?
The LT3491ESC8 includes internal open-LED protection that clamps the CAP pin voltage at 27V (typical), as verified in Electrical Characteristics (CAP Pin Overvoltage Protection = 26–28V) and Typical Performance Graph G05. During an open-LED event, the device reduces switching frequency to minimize input current draw while maintaining safe voltage levels - preventing damage to the output capacitor or surrounding circuitry.
Can the LT3491ESC8 operate from a 2.5V input supply?
Yes, the LT3491ESC8 supports a minimum input voltage of 2.5V, as specified in Absolute Maximum Ratings and Electrical Characteristics tables. It has been validated in low-input applications such as powering three LEDs from two AA cells (2.0–3.2V), with the inductor driven from the battery while the IC itself is powered from a separate 3.3V logic rail - ensuring reliable startup and regulation even at the 2.5V lower limit.
LT3491ESC8 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- True Color PWM™
- Package/Case:
- 8-VFSOP (0.049", 1.25mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- DC DC Regulator
- Topology:
- Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 2.5V
- Voltage - Supply (Max):
- 12V
- Voltage - Output:
- 27V
- Current - Output / Channel:
- 350mA (Switch)
- Frequency:
- 2.3MHz
- Dimming:
- PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SC-70-8
LT3491ESC8 FAQ
1.How can I place an order for LT3491ESC8 through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3491ESC8 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 LT3491ESC8 reliable?
The price and inventory of LT3491ESC8 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3491ESC8 is usually 5 days.
3.What payment methods are accepted for LT3491ESC8?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3491ESC8 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3491ESC8?
LT3491ESC8 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3491ESC8 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 LT3491ESC8?
For technical support, including LT3491ESC8 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3491ESC8 requirements.
6.How does Aetrix verify that LT3491ESC8 is sourced from the original manufacturer or authorized distributors?
All LT3491ESC8 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 LT3491ESC8 meets industry standards.
7.What is the process for return or replacement of LT3491ESC8?
All LT3491ESC8 units undergo pre-shipment inspection (PSI). If there is an issue with LT3491ESC8, 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 LT3491ESC8 part is unused and in its original packaging.
Return procedure for LT3491ESC8:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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