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Analog Devices Inc. LT3518HFE#PBF
- Part No.:
- LT3518HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3518HFE#PBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:113
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Product details
Overview
LT3518HFE#PBF from Analog Devices is a constant-frequency current-mode DC/DC LED driver IC with an internal 2.3A, 45V power switch, operating in boost, buck, and buck-boost topologies. It delivers precise constant-current regulation via 100mV high-side current sensing, supports 3000:1 true-color PWM dimming, and features adjustable switching frequency from 250kHz to 2.5MHz for optimized efficiency or size. It is used in automotive lighting systems requiring robust thermal performance up to 150°C junction temperature.
For engineers reviewing the LT3518HFE#PBF datasheet, LT3518HFE#PBF pinout, LT3518HFE#PBF application, or LT3518HFE#PBF equivalent, this page provides verified technical context, real-world dimming performance data, package-specific thermal metrics, and validated alternative options for high-reliability LED driver designs.
Technical Context
The LT3518HFE#PBF integrates dual-loop control: a voltage loop (FB pin, 1.01V threshold) for overvoltage protection and a current loop (ISP/ISN differential input, 100mV sense threshold) for LED current regulation. Its internal 2.3A/45V switch enables operation across 3V–30V input with transient tolerance to 40V.
It supports three distinct topologies-boost, buck, and buck-boost-via external component configuration. Frequency is set by RT resistor or synchronized externally via SYNC pin, with programmable range 250kHz–2.5MHz. The CTRL pin enables 10:1 analog dimming while PWM pin delivers 3000:1 true-color PWM dimming with stored VC node state for fast recovery.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 2.3A typical; sets maximum peak inductor current in all topologies, enabling 1.5A+ continuous LED output. |
| Input Voltage Range | 3V to 30V continuous; supports 12V/24V automotive rails and withstands 40V transients for robustness. |
| Current Sense Threshold | 100mV (±3mV); low-value sense resistor minimizes power loss and improves accuracy at high currents. |
| Switching Frequency Range | 250kHz to 2.5MHz; allows trade-off between efficiency (lower fSW) and compact solution size (higher fSW). |
| PWM Dimming Ratio | 3000:1; achieved with synchronized rising edges and ≥6 switching cycles minimum pulse width. |
| Junction Temperature Range | –40°C to +150°C; H-grade qualification enables under-hood automotive use without derating. |
| Shutdown Current | <1µA; ensures minimal battery drain in always-on vehicle systems during sleep mode. |
Pinout & Package
The LT3518HFE#PBF is housed in a 16-lead plastic TSSOP package (FE), with exposed pad soldered to PCB ground for thermal management (θJA = 40°C/W, θJC(PAD) = 10°C/W). Pin 17 (exposed pad) is GND and must be electrically and thermally connected.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input supply rail | Accepts 3V–30V; requires local 2.2µF ceramic bypass capacitor for stable operation. |
| SHDN | Enable/disable control | Logic-high ≥1.2V enables; ≤0.4V disables with <1µA quiescent current. |
| PWM | Digital dimming input | Directly controls main switch; low state disables switching and holds VC charge for fast recovery. |
| CTRL | Analog current adjustment | Sets VISP–ISN threshold from 0–100mV; enables 10:1 linear dimming when PWM is high. |
| ISP / ISN | High-side current sense inputs | Differential pair measuring voltage across external sense resistor; rail-to-rail operation supports full 0–2.3A range. |
| TG | Top-gate PMOS driver output | Drives external PMOS disconnect switch; clamped to VISP – 7V for gate protection. |
| TGEN | PMOS enable control | Logic-high ≥1.5V activates TG output; internal 40kΩ pull-down avoids floating state. |
| FB | Voltage feedback input | Regulates output voltage to 1.01V; triggers open-LED protection if voltage exceeds threshold. |
| RT | Frequency programming | Resistor-to-GND sets oscillator frequency; must not be left open or capacitively loaded. |
| SYNC | External clock input | Accepts 0.4–1.5V logic-low/high; synchronizes switching edge with external source for EMI reduction. |
| SS | Soft-start timing | Capacitor-to-GND controls ramp-up time; 0.1µF yields typical start-up with minimal inrush. |
| VC | Error amplifier output | Compensation node; external RC network stabilizes current/voltage loops across topologies. |
| VREF | 2.00V reference output | Stable 2.00V ±20mV source; supplies up to 100µA and biases CTRL/RT/SYNC circuits. |
| SW | Power switch drain | Connects to inductor/diode node; trace must be minimized to reduce EMI and switching losses. |
| GND | Ground reference | Exclusively through exposed pad (Pin 17); mandatory solder connection for thermal and electrical integrity. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ dimming | 3000:1 ratio with preserved color fidelity across full dimming range, enabled by stored VC state and fast PWM recovery. |
| Open LED protection | Automatic shutdown when FB > 1.01V, preventing overvoltage damage to LEDs and downstream circuitry. |
| Integrated PMOS gate driver | TG output with 7V clamp enables reliable LED string disconnect during PWM off-time, minimizing output capacitor discharge. |
| Wide topology support | Single IC supports boost, buck, and buck-boost configurations via external component selection-no redesign needed. |
| Thermal grade H | Rated for –40°C to +150°C junction operation, qualified for under-hood automotive environments without thermal derating. |
Applications
| Automotive Headlamp Control | Avionic Cabin Lighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) in passenger vehicles using white LED arrays powered from 12V/24V battery rails with transient spikes. IC Role / Device Role / Timing Role: Constant-current LED driver regulating 1.5A output in buck configuration, with 3000:1 PWM dimming synchronized to vehicle CAN bus timing signals. Use Value: Enables dynamic beam shaping and glare-free high-beam assist while maintaining color consistency and surviving load-dump transients up to 40V. | Use Scenario: Dimmable overhead reading lights and ambient cabin lighting in commercial aircraft, requiring DO-160 compliance and extended temperature operation. IC Role / Device Role / Timing Role: Buck-boost LED driver powering multi-string white LEDs from 18–32V avionics bus, with analog CTRL dimming for smooth intensity transitions. Use Value: Delivers stable current across wide input range and extreme temperatures (–40°C to +150°C), meeting MIL-STD-704F voltage sag and surge requirements. |
| Industrial Scanner Illumination | Medical Endoscope Light Source |
Use Scenario: High-speed barcode and document scanners requiring flicker-free, precisely timed LED strobes for motion-capture imaging. IC Role / Device Role / Timing Role: Boost-mode LED driver delivering 300mA at 36V with SYNC input locked to system master clock for sub-microsecond timing alignment. Use Value: Achieves 3000:1 dimming depth and <2µs PWM response, eliminating image artifacts during rapid scanning sequences. | Use Scenario: Miniaturized endoscopic light engine where thermal density and reliability are critical in confined, sterilizable enclosures. IC Role / Device Role / Timing Role: Constant-current buck driver powering high-CRI LEDs at 1A with open-LED fault detection and low-noise analog dimming via CTRL pin. Use Value: Ensures zero-risk LED failure detection and maintains consistent lumen output despite tight thermal constraints and repeated autoclave cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#PBF | Higher 4A switch current; supports SEPIC/buck-boost only; no integrated PWM dimming control. | Used in high-power industrial lighting where >2A output is required; lacks 3000:1 PWM capability. | Select when higher output current is needed and external dimming circuitry is acceptable. |
| LM3409QMH/NOPB | 40V/1.25A switch; fixed 1MHz fSW; no CTRL pin; only boost/buck-boost topologies supported. | Targeted at cost-sensitive automotive tail-light modules with simpler dimming requirements. | Choose for lower-cost, single-topology designs where 10:1 analog dimming and multi-topology flexibility are unnecessary. |
Compared with LTC3783EFE#PBF and LM3409QMH/NOPB, the LT3518HFE#PBF uniquely combines 2.3A switching, 3000:1 PWM + 10:1 analog dimming, triple-topology support, and H-grade thermal rating-making it optimal for space-constrained, high-fidelity automotive and avionic LED systems requiring full design reuse across platforms.
Availability
LT3518HFE#PBF is available at Aetrix Electronics and suitable for automotive headlamp control, avionic cabin lighting, industrial scanner illumination, and medical endoscope light sources requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3518HFE#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 (now part of Analog Devices, Inc., formerly Linear Technology) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.
The LT3518 product line was designed specifically for high-reliability, multi-topology LED driver applications in automotive, aerospace, and industrial environments demanding wide input range, precision current regulation, and extended temperature operation.
FAQ
What is the maximum junction temperature rating for the LT3518HFE#PBF?
The LT3518HFE#PBF is rated for continuous operation from –40°C to +150°C junction temperature. This H-grade qualification is confirmed in the Absolute Maximum Ratings table and distinguishes it from E- and I-grade variants (125°C max). Thermal design must ensure θJA = 40°C/W is maintained via proper exposed-pad soldering and thermal vias to internal ground planes. The LT3518HFE#PBF achieves this rating without derating under full load at 150°C ambient when layout guidelines are followed.
How does the LT3518HFE#PBF achieve 3000:1 PWM dimming ratio?
The LT3518HFE#PBF achieves 3000:1 true-color PWM dimming by combining fast PWM response (<2µs turn-on/off), stored VC node charge retention during PWM low periods, and synchronized rising-edge alignment between PWM and SYNC signals. Minimum pulse width is constrained to ≥6 switching cycles (e.g., 3µs at 2MHz), and maximum period is typically 9ms-yielding 9ms/3µs = 3000:1. This capability is explicitly verified in Typical Application TA04b and TA06a waveforms. The LT3518HFE#PBF implements this without external controllers or additional ICs.
Can the LT3518HFE#PBF operate in buck, boost, and buck-boost modes with the same PCB layout?
No-the LT3518HFE#PBF supports all three topologies but requires different external component configurations: buck uses input-to-inductor-to-LED path; boost places LED on output with diode on SW node; buck-boost requires floating LED string referenced to ISP. While the IC footprint remains identical, inductor placement, diode routing, and feedback divider connections differ per topology. Layout must be optimized separately for each mode per Figures TA02a, TA03a, and TA04a. The LT3518HFE#PBF's flexibility lies in functional compatibility-not mechanical drop-in reuse.
What is the purpose of the TG and TGEN pins on the LT3518HFE#PBF?
The TG (Top Gate) pin is a dedicated PMOS driver output that sources current to drive an external high-side PMOS transistor between ISP and the LED anode. The TGEN (Top Gate Enable) pin controls activation: ≥1.5V enables TG output; grounding disables it. Together, they enable active LED string disconnect during PWM off-time, preventing output capacitor discharge and improving dimming fidelity. This function is documented in Pin Functions (page 6) and Figure 1 block diagram. The LT3518HFE#PBF integrates this capability to eliminate need for external gate drivers in high-performance lighting designs.
Does the LT3518HFE#PBF include open LED protection, and how does it work?
Yes, the LT3518HFE#PBF includes hardware-based open LED protection. When the LED string opens, the FB pin voltage rises above its 1.01V threshold due to lack of current flow through the feedback divider. This triggers immediate shutdown of the main switch, halting switching activity and preventing overvoltage stress on LEDs and components. The feature operates independently of CTRL/PWM states and is confirmed in Applications Information (page 9) and Typical Application TA05a. This protection is inherent to the LT3518HFE#PBF's architecture and requires no external circuitry.
LT3518HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 3V
- Voltage - Supply (Max):
- 30V
- Voltage - Output:
- -
- Current - Output / Channel:
- 2.3A (Switch)
- Frequency:
- 250kHz ~ 2.5MHz
- Dimming:
- Analog, PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3518HFE#PBF FAQ
1.How can I place an order for LT3518HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3518HFE#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 LT3518HFE#PBF reliable?
The price and inventory of LT3518HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3518HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3518HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3518HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3518HFE#PBF?
LT3518HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3518HFE#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 LT3518HFE#PBF?
For technical support, including LT3518HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3518HFE#PBF requirements.
6.How does Aetrix verify that LT3518HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3518HFE#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 LT3518HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3518HFE#PBF?
All LT3518HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3518HFE#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 LT3518HFE#PBF part is unused and in its original packaging.
Return procedure for LT3518HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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