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Analog Devices Inc. LT3518HUF#TRPBF
- Part No.:
- LT3518HUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WQFN Exposed Pad
- Datasheet:
-
LT3518HUF#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 2.3A 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,252
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Product details
Overview
LT3518HUF#TRPBF from Analog Devices is a constant-frequency current-mode DC/DC LED driver IC with an internal 2.3A, 45V power switch, supporting boost, buck, and buck-boost topologies. It delivers precise constant-current regulation via a 100mV high-side current sense and enables 3000:1 true-color PWM dimming for high-fidelity display backlighting in automotive and avionic systems.
For engineers reviewing the LT3518HUF#TRPBF datasheet, LT3518HUF#TRPBF pinout, LT3518HUF#TRPBF application, or LT3518HUF#TRPBF equivalent, key selection criteria include its –40°C to 150°C operating junction temperature, 250kHz–2.5MHz adjustable switching frequency, open-LED protection, and integrated PMOS gate driver for LED disconnect.
Technical Context
The LT3518HUF#TRPBF implements dual-loop regulation: a voltage loop (FB pin, 1.01V threshold) for overvoltage protection and a current loop (ISP/ISN differential input, 100mV full-scale threshold) for LED current control. Its internal transconductance error amplifier (550µS) drives the VC pin to stabilize either loop based on real-time demand.
Switching is controlled by a current-mode oscillator whose frequency is set via RT resistor (250kHz–2.5MHz) or synchronized externally via SYNC pin. The device integrates a top-gate driver (TG) with 7V clamp for PMOS LED disconnect, and supports analog dimming via CTRL pin (0–1V input, 10:1 range) alongside digital PWM dimming (3000:1).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Junction Temp | –40°C to 150°C - enables use in under-hood automotive and high-ambient industrial lighting without derating. |
| Internal Switch Rating | 2.3A continuous, 45V breakdown - supports high-brightness LED strings up to ~100W in boost configuration. |
| Current Sense Threshold | 100mV ±3% - minimizes power loss in sense resistor while enabling accurate LED current regulation. |
| Dimming Capability | 3000:1 PWM + 10:1 analog - achieves flicker-free, high-contrast dimming across full brightness range. |
| Switching Frequency Range | 250kHz to 2.5MHz - allows optimization between efficiency (low fSW) and compact solution size (high fSW). |
| Input Voltage Range | 3V to 30V continuous, 40V transient - accommodates 12V/24V automotive rails with surge tolerance. |
| Protection Features | Open-LED detection, thermal shutdown, overvoltage (FB), and undervoltage lockout - ensures robust operation in safety-critical lighting. |
Pinout & Package
The LT3518HUF#TRPBF is housed in a 16-lead (4mm × 4mm) plastic QFN package with exposed thermal pad (Pin 17 = GND). This thermally enhanced package delivers θJA = 36°C/W and requires soldering of the exposed pad to PCB ground plane for reliable operation at 150°C junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW | Power switch drain node | High-frequency switching node; must be minimized in area to reduce EMI and layout parasitics. |
| VIN | Main input supply | Accepts 3V–30V; requires local low-ESR ceramic bypass capacitor (≥1µF) 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 to 1.01V threshold; used for overvoltage protection in constant-current LED mode. |
| VC | Error amplifier output | gm = 550µS; connects to external RC compensation network to stabilize current/voltage loops. |
| CTRL | Analog dimming control | 0–1V input sets LED current threshold (ILED = VCTRL/(10·RSENSE)); tie to VREF for full-scale 100mV. |
| PWM | Digital dimming input | Active-low signal disables switching and saves VC state; enables 3000:1 true-color PWM dimming. |
| TG | Top-gate driver output | Drives external PMOS between ISP and load; clamped to VISP – 7V for safe gate drive. |
| ISP / ISN | High-side current sense inputs | Differential pair measuring voltage across external sense resistor; rail-to-rail operation supports wide LED voltage range. |
| RT | Frequency adjustment | Resistor-to-GND sets oscillator frequency (250kHz–2.5MHz); must not be left floating or capacitive-loaded. |
| SYNC | External clock input | Accepts external clock; RT resistor must be selected for 20% lower free-running frequency than SYNC signal. |
| SS | Soft-start control | Capacitor-to-GND controls ramp-up time; typical value 0.1µF reduces inrush current and output overshoot. |
| VREF | 2.0V reference output | Stable 2.0V ±2% reference; supplies up to 100µA; used to bias CTRL pin or external circuitry. |
| TGEN | PMOS driver enable | Logic-high (>1.5V) enables TG output; internal 40kΩ pull-down ensures disable when unconnected. |
| GND (EP) | Ground / Thermal pad | Exposed pad (Pin 17) is sole GND connection; must be soldered to PCB ground plane with thermal vias. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ Dimming | 3000:1 ratio preserves color fidelity across dimming range by maintaining consistent LED forward voltage and spectral output. |
| Integrated PMOS Gate Driver | TG pin drives external PMOS to disconnect LED string during PWM off-time, preventing output capacitor discharge and improving transient recovery. |
| Wide Input Voltage Range | 3V–30V operation with 40V transient tolerance supports direct connection to 12V/24V vehicle batteries without pre-regulation. |
| Multi-Topology Flexibility | Native support for boost, buck, and buck-boost configurations enables single-IC solutions across diverse LED voltage and current requirements. |
| Open-LED Protection | Monitors ISP/ISN differential voltage; shuts down switch and asserts fault condition if sense voltage exceeds threshold, preventing overvoltage damage. |
| Adjustable Switching Frequency | 250kHz–2.5MHz via RT resistor or SYNC pin allows trade-off between efficiency (lower fSW) and component size (higher fSW). |
Applications
| Automotive Headlamp Control | Avionic Display Backlighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) requiring dynamic beam shaping and intensity modulation across temperature extremes. IC Role / Device Role / Timing Role: Constant-current LED driver regulating high-power white LED arrays in buck-boost configuration with open-circuit fault detection. Use Value: –40°C to 150°C guaranteed operation eliminates need for external thermal derating; 3000:1 PWM dimming enables smooth glare-free transitions between low/high beam modes. | Use Scenario: Cockpit LCD backlight requiring flicker-free, high-contrast illumination under varying ambient light and vibration conditions. IC Role / Device Role / Timing Role: Boost-mode constant-current driver powering multi-string LEDs with tight current matching and fast PWM response. Use Value: 100mV current sense threshold minimizes power loss in sense resistor; integrated soft-start prevents display flash during power-up sequences. |
| Industrial Scanner Illumination | Medical Endoscope Lighting |
Use Scenario: High-speed barcode scanner requiring uniform, strobed LED illumination synchronized to image capture timing. IC Role / Device Role / Timing Role: Buck-mode LED driver with external SYNC input locked to camera trigger signal for precise pulse alignment. Use Value: SYNC pin accepts external clock up to 2.5MHz; 200ns gate turn-on/off delays ensure sub-microsecond LED activation timing accuracy. | Use Scenario: Sterilizable endoscope with embedded LED light source needing stable current delivery despite thermal cycling and space constraints. IC Role / Device Role / Timing Role: Compact QFN-based constant-current driver in boost topology, leveraging exposed pad for passive thermal management inside sealed housing. Use Value: 4mm × 4mm QFN package fits tight optical assemblies; open-LED protection prevents hazardous overvoltage if fiber-optic coupling fails. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#TRPBF | Higher 4A switch current, 60V rating, but no integrated current sense amplifier; requires external sense amp and compensation. | Targeted at higher-power (>20W) LED arrays where programmable current limit and external loop control are preferred. | Select when >2.3A peak current or >45V operation is required; accept added BOM complexity for flexibility. |
| LM3409QMH/NOPB | Lower 1.25A switch current, 42V rating, fixed 100mV sense threshold, no analog dimming (CTRL) or TG driver. | Suitable for cost-sensitive, lower-power automotive interior lighting where only PWM dimming is needed. | Select for simpler, lower-cost designs below 1.25A; avoid when analog dimming, PMOS disconnect, or >150°C operation is required. |
Compared with LTC3783EFE#TRPBF and LM3409QMH/NOPB, the LT3518HUF#TRPBF uniquely combines 2.3A/45V switching, integrated 100mV current sense, analog+PWM dimming, and –40°C to 150°C operation in a single 4mm × 4mm QFN - making it optimal for space-constrained, high-reliability LED lighting where thermal margin and dimming fidelity are critical.
Availability
LT3518HUF#TRPBF is available at Aetrix Electronics and suitable for automotive headlamps, avionic displays, industrial scanners, and medical endoscopes requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3518HUF#TRPBF 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 Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.
The LT3518HUF#TRPBF belongs to ADI's Power by Linear™ LED driver product line, engineered specifically for high-reliability, wide-temperature-range constant-current LED lighting in safety-critical environments.
FAQ
What is the maximum junction temperature specification for the LT3518HUF#TRPBF?
The LT3518HUF#TRPBF is rated for a maximum operating junction temperature of 150°C, with guaranteed performance across –40°C to 150°C. This H-grade temperature rating distinguishes it from E-grade (–40°C to 125°C) and I-grade (–40°C to 125°C) variants, making the LT3518HUF#TRPBF suitable for under-hood automotive and high-ambient industrial applications where thermal margin is critical. The exposed pad must be soldered to a PCB ground plane with thermal vias to maintain this rating.
How does the LT3518HUF#TRPBF achieve 3000:1 PWM dimming ratio?
The LT3518HUF#TRPBF achieves 3000:1 true-color PWM dimming by combining precise switch timing control, stored VC node state during PWM low periods, and optional external PMOS LED disconnect via the TG pin. Minimum PWM pulse width is constrained by switching frequency (e.g., ≥3µs at 2MHz), and maximum period is typically ≤12ms. The formula PWMRATIO = tMAX/tMIN yields 3000:1 when tMAX = 9ms and tMIN = 3µs. This capability is fully supported in the LT3518HUF#TRPBF without external circuitry.
Can the LT3518HUF#TRPBF operate in buck, boost, and buck-boost topologies with the same pin configuration?
Yes, the LT3518HUF#TRPBF supports all three topologies using identical pin connections - its architecture adapts based on external component configuration, not internal pin reassignment. In buck mode, VIN powers the LED cathode side; in boost, VIN feeds the inductor input; in buck-boost, VIN connects to the coupled inductor center tap. The ISP/ISN current sense, FB voltage feedback, and TG PMOS driver remain functionally consistent across topologies, enabling flexible design reuse of the LT3518HUF#TRPBF across multiple lighting architectures.
What is the purpose of the TGEN pin on the LT3518HUF#TRPBF?
The TGEN pin on the LT3518HUF#TRPBF enables or disables the integrated top-gate driver (TG pin). When TGEN is pulled high (>1.5V), the TG output actively drives an external PMOS transistor to disconnect the LED string during PWM off-time - preventing output capacitor discharge and reducing transient recovery time. When TGEN is grounded or left floating (internal 40kΩ pull-down), the TG pin is disabled and remains high-impedance. This feature is essential for high-fidelity PWM dimming in boost and buck-boost configurations where output capacitance would otherwise sustain LED current.
Does the LT3518HUF#TRPBF require external compensation components, and where are they connected?
Yes, the LT3518HUF#TRPBF requires external compensation components connected to the VC pin to stabilize its transconductance error amplifier loop. A typical configuration uses a 10nF capacitor from VC to GND; a series resistor may be added to increase slew rate for improved transient response to VIN or CTRL changes. Compensation is necessary for both constant-current (ISP/ISN loop) and constant-voltage (FB loop) operation, and values depend on selected inductor, output capacitor, and topology. No compensation is required on other pins such as RT or SS.
LT3518HUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT3518HUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3518HUF#TRPBF 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#TRPBF reliable?
The price and inventory of LT3518HUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3518HUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3518HUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3518HUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3518HUF#TRPBF?
LT3518HUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3518HUF#TRPBF 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#TRPBF?
For technical support, including LT3518HUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3518HUF#TRPBF requirements.
6.How does Aetrix verify that LT3518HUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3518HUF#TRPBF 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#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3518HUF#TRPBF?
All LT3518HUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3518HUF#TRPBF, 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#TRPBF part is unused and in its original packaging.
Return procedure for LT3518HUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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