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Analog Devices Inc. LT3518HUF#PBF
- Part No.:
- LT3518HUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WQFN Exposed Pad
- Datasheet:
-
LT3518HUF#PBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 2.3A 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,192
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Product details
Overview
LT3518HUF#PBF from Analog Devices is a constant-frequency current-mode DC/DC LED driver IC with an internal 2.3A, 45V N-channel MOSFET switch, supporting boost, buck, and buck-boost topologies. It delivers precise constant-current regulation via 100mV high-side current sensing and enables 3000:1 true-color PWM dimming for high-fidelity display backlighting in automotive and avionic systems.
For engineers reviewing the LT3518HUF#PBF datasheet, LT3518HUF#PBF pinout, LT3518HUF#PBF application, or LT3518HUF#PBF equivalent, key selection criteria include its –40°C to 150°C operating junction temperature, 250kHz–2.5MHz adjustable switching frequency, open-LED protection, and gate driver for external PMOS LED disconnect-critical for robust illumination control in thermally demanding environments.
Technical Context
The LT3518HUF#PBF integrates dual feedback loops: a voltage loop (FB pin, 1.01V threshold) for overvoltage protection and a current loop (ISP/ISN, 100mV sense threshold) for LED current regulation. Its error amplifier (A3) selects the lower of the two loop outputs to enforce seamless transition between constant-current and constant-voltage modes.
It features synchronous frequency adjustment via SYNC pin (with RT resistor set 20% below external clock), soft-start control (SS pin), and independent PWM dimming (3000:1) plus analog dimming (10:1 via CTRL pin). The TG output drives an external PMOS for LED string disconnection during PWM low periods, minimizing output capacitor discharge and improving transient recovery.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 2.3A typical; ensures reliable drive for high-brightness LED strings up to 30W in buck-boost configurations. |
| Input Voltage Range | 3V to 30V continuous, 40V transient; supports wide-input industrial and automotive power rails without external protection. |
| Current Sense Threshold | 100mV at ISP–ISN; enables accurate, low-loss LED current regulation with minimal thermal drift across temperature. |
| Switching Frequency Range | 250kHz to 2.5MHz; allows optimization of inductor size (e.g., 4.3µH at 2MHz) vs. efficiency (e.g., 15µH at 1MHz). |
| Operating Junction Temp | –40°C to 150°C; qualified for under-hood automotive lighting and high-ambient industrial enclosures. |
| PWM Dimming Ratio | 3000:1 true-color; preserves color fidelity across full brightness range in display backlight applications. |
| Shutdown Current | <1µA; enables ultra-low-power standby in battery-backed illumination systems. |
Pinout & Package
The LT3518HUF#PBF is housed in a 16-lead (4mm × 4mm) plastic QFN package with exposed thermal pad (Pin 17) soldered to PCB ground for thermal management (θJA = 36°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW | Power Switch Output | Drives external inductor/diode; requires minimized trace area to reduce EMI and switching losses. |
| VIN | Main Input Supply | Accepts 3V–30V input; must be bypassed with ≥1µF ceramic capacitor placed adjacent to pin. |
| SHDN | Enable/Disable Control | Logic-high (>1.2V) enables operation; logic-low (<0.4V) reduces quiescent current to <1µA. |
| FB | Voltage Feedback Input | Regulates output voltage to 1.01V threshold; used for overvoltage protection in boost/buck-boost modes. |
| CTRL | Analog Dimming Input | Sets current sense threshold from 0–100mV (0–1V input); provides 10:1 linear dimming ratio when PWM is active. |
| PWM | Digital Dimming Input | Directly gates main switch; low state disables switching and saves VC node charge for fast recovery. |
| TG | Top-Gate Driver Output | Drives external PMOS source-to-VISP; clamped to VISP – 7V for safe gate drive in high-side disconnect. |
| ISP / ISN | High-Side Current Sense Inputs | Differential pair measuring voltage across external sense resistor; rail-to-rail operation supports full LED string voltage range. |
| RT | Frequency Adjustment | Resistor-to-ground sets oscillator frequency; 16.9kΩ yields 1MHz, enabling compact magnetics design. |
| SYNC | External Clock Input | Accepts TTL/CMOS clock; forces synchronized switching with 20% slower RT-set base frequency. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 2.3A/45V Power Switch | Eliminates external MOSFET and associated gate drive complexity in space-constrained LED drivers. |
| True Color PWM™ Dimming | 3000:1 ratio with no color shift-achieved by preserving VC node charge state during PWM off-time. |
| Open LED Protection | Automatic shutdown if ISP–ISN voltage exceeds threshold, preventing overvoltage damage to LED string. |
| PMOS Gate Driver (TG) | Enables fast, low-loss LED string disconnection during PWM low phase, reducing output capacitor discharge. |
| Adjustable Frequency (250kHz–2.5MHz) | Allows trade-off between efficiency (lower fSW) and solution size (higher fSW) without redesigning compensation. |
Applications
| Automotive Headlight Modules | Avionic Display Backlighting |
|---|---|
Use Scenario: High-intensity LED arrays in adaptive front-lighting systems requiring thermal resilience and EMI control. IC Role / Device Role / Timing Role: Constant-current LED driver with open-LED fault detection and PMOS disconnect for fail-safe operation. Use Value: 150°C junction rating enables direct mounting near heat-generating optics; 3000:1 dimming supports dynamic beam shaping without color distortion. | Use Scenario: Cockpit LCD backlighting where reliability, color accuracy, and low EMI are mission-critical. IC Role / Device Role / Timing Role: Synchronized buck-boost LED driver with 120Hz PWM dimming and tight current regulation. Use Value: SYNC pin allows alignment with display frame timing; 100mV current sense minimizes power loss and thermal rise in sealed enclosures. |
| Industrial Scanner Illumination | Medical Endoscope Lighting |
Use Scenario: Pulsed high-brightness LED illumination in barcode and document scanners requiring rapid on/off transitions. IC Role / Device Role / Timing Role: Fast-recovery buck-mode driver with stored VC node charge and external PMOS disconnect. Use Value: Sub-microsecond PWM recovery time ensures consistent exposure per scan line; 2.3A switch supports multi-LED parallel strings. | Use Scenario: Sterilizable, compact LED light sources in flexible endoscopes with strict thermal and size constraints. IC Role / Device Role / Timing Role: Thermally robust constant-current driver with analog + PWM dimming for precise intensity control. Use Value: Exposed-pad QFN package enables direct thermal coupling to metal housing; 10:1 CTRL dimming adds fine-grained adjustment atop 3000:1 PWM range. |
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, fixed 500kHz frequency, no integrated current sense amplifier. | Requires external current sense amp and resistor network; better suited for high-power (>30W), fixed-frequency designs. | Select when higher output power and simplified frequency control outweigh need for programmable dimming and integrated sensing. |
| LM3409QMH/NOPB | 40V/1.25A switch, 100mV sense, but only boost topology support and no TG driver. | Lacks buck/buck-boost capability and PMOS disconnect; limited to single-topology LED strings with lower current. | Choose for cost-sensitive boost-only automotive lighting where 1.25A max current suffices and thermal grade is less critical. |
Compared with LTC3783EFE#PBF and LM3409QMH/NOPB, the LT3518HUF#PBF uniquely combines triple topology flexibility, integrated current sense amplifier, TG driver for LED disconnect, and extended 150°C operation-making it optimal for compact, thermally aggressive, multi-mode LED systems requiring both precision dimming and fault resilience.
Availability
LT3518HUF#PBF is available at Aetrix Electronics and suitable for automotive headlight modules, avionic display backlighting, and industrial scanner illumination requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3518HUF#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.) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3518 product line was designed specifically for high-reliability, multi-topology LED driving in thermally demanding environments-emphasizing precision current regulation, wide input range, and integrated protection features for automotive and aerospace lighting.
FAQ
What is the maximum junction temperature rating for the LT3518HUF#PBF?
The LT3518HUF#PBF is guaranteed over the full –40°C to 150°C operating junction temperature range. This H-grade qualification distinguishes it from E- and I-grade variants (rated to 125°C) and enables deployment in under-hood automotive and high-ambient industrial applications where thermal derating is critical. The exposed pad must be soldered to a PCB ground plane with thermal vias to maintain this rating.
How does the LT3518HUF#PBF achieve 3000:1 PWM dimming without color shift?
The LT3518HUF#PBF achieves 3000:1 true-color PWM dimming by preserving the charge state on the VC pin during PWM low periods-disabling the main switch while retaining the error amplifier's demand current. When PWM goes high, the stored VC voltage enables immediate current restoration, eliminating settling delay and maintaining consistent LED forward voltage and chromaticity across the entire dimming range.
Can the LT3518HUF#PBF operate in buck, boost, and buck-boost topologies with the same PCB layout?
No-the LT3518HUF#PBF supports all three topologies functionally, but each requires distinct external component placement and routing. Buck mode places the LED string between PVIN and SW; boost mode places it between SW and output capacitor; buck-boost uses floating inductor configuration. Component values (inductor, sense resistor, feedback dividers) and layout (especially SW node area and grounding) must be optimized per topology-no universal layout exists.
What is the role of the TG pin on the LT3518HUF#PBF, and how is it used?
The TG pin on the LT3518HUF#PBF is a top-gate driver output that drives the gate of an external PMOS transistor connected between VISP and the LED anode. When enabled via TGEN, it provides inverted PWM control to disconnect the LED string during PWM low periods-preventing output capacitor discharge and enabling faster dimming recovery. Its internal 7V clamp ensures safe gate drive even when VISP reaches 45V.
Does the LT3518HUF#PBF require external compensation components, and what are typical values?
Yes-the LT3518HUF#PBF uses an internal transconductance error amplifier with VC pin output requiring external RC compensation. For most LED applications, a 10nF capacitor from VC to GND is sufficient; a series resistor is optional and used only to increase slew rate during fast VIN or CTRL transients. The compensation network stabilizes the current and voltage loops, with values dependent on selected inductor and output capacitance.
LT3518HUF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WQFN 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-QFN (4x4)
LT3518HUF#PBF FAQ
1.How can I place an order for LT3518HUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3518HUF#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 LT3518HUF#PBF reliable?
The price and inventory of LT3518HUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3518HUF#PBF is usually 5 days.
3.What payment methods are accepted for LT3518HUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3518HUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3518HUF#PBF?
LT3518HUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3518HUF#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 LT3518HUF#PBF?
For technical support, including LT3518HUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3518HUF#PBF requirements.
6.How does Aetrix verify that LT3518HUF#PBF is sourced from the original manufacturer or authorized distributors?
All LT3518HUF#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 LT3518HUF#PBF meets industry standards.
7.What is the process for return or replacement of LT3518HUF#PBF?
All LT3518HUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3518HUF#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 LT3518HUF#PBF part is unused and in its original packaging.
Return procedure for LT3518HUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3518HUF#PBF Tags
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