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Analog Devices Inc. LT3517HUF#PBF
- Part No.:
- LT3517HUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WQFN Exposed Pad
- Datasheet:
-
LT3517HUF#PBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 1.5A 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,974
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Product details
Overview
LT3517HUF#PBF from Analog Devices is a constant-frequency current-mode DC/DC LED driver IC with an integrated 1.5A, 45V internal power switch, operating in boost, buck, and buck-boost topologies. It delivers precise constant-current regulation via 100mV high-side current sensing, supports 250kHz–2.5MHz adjustable switching frequency, and enables 5000:1 true-color PWM dimming for automotive lighting and display backlighting.
For engineers reviewing the LT3517HUF#PBF datasheet, LT3517HUF#PBF pinout, LT3517HUF#PBF application, or LT3517HUF#PBF equivalent, key selection criteria include its –40°C to 150°C junction temperature rating, QFN-16 (4mm × 4mm) package with exposed thermal pad, open-LED protection, and dual-loop (voltage + current) regulation architecture enabling seamless mode transitions.
Technical Context
The LT3517HUF#PBF implements a dual-loop control architecture: a voltage feedback loop (FB pin, 1.01V threshold) and a current feedback loop (ISP/ISN differential sense, 100mV full-scale), where the lower demand dominates to enforce either constant-voltage or constant-current regulation. Its internal 1.5A/45V N-channel MOSFET switch operates with current-mode control using a stabilizing ramp and PWM comparator.
It integrates a transconductance error amplifier (550µS) at the VC pin for loop compensation, supports external synchronization (SYNC pin), programmable soft-start (SS pin), and provides a dedicated PMOS gate driver (TG pin) with 7V clamp for LED string disconnect-enabling fast PWM dimming recovery and load dump protection in automotive environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.5A typical; sets maximum peak inductor current to prevent saturation and ensure safe operation under transient loads. |
| Input Voltage Range | 3V to 30V continuous, 40V transient; supports wide automotive battery range including cold-crank and load-dump conditions. |
| Current Sense Threshold | 100mV ±3% at ISP–ISN; enables accurate LED current regulation with low-power, high-precision shunt resistor selection. |
| Switching Frequency Range | 250kHz to 2.5MHz via RT resistor; allows optimization of inductor size, efficiency, and EMI profile for space-constrained designs. |
| Junction Temperature Range | –40°C to 150°C; qualified for under-hood automotive and high-reliability industrial LED lighting applications. |
| PWM Dimming Ratio | 5000:1 true-color ratio; achieved by external PWM signal controlling main switch enable/disable with stored VC state for minimal recovery delay. |
| Analog Dimming Range | 10:1 via CTRL pin (0–1V); linearly scales current sense threshold to extend total dimming range when combined with PWM. |
Pinout & Package
The LT3517HUF#PBF is housed in a 16-lead (4mm × 4mm) plastic QFN package with exposed thermal pad (Pin 17) that must be soldered to PCB ground for thermal and electrical integrity. Thermal resistance θJA = 36°C/W, θJC(PAD) = 10°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW | Power Switch Output | Drives external inductor/diode network; high di/dt node requiring minimized trace area to reduce EMI. |
| VIN | Main Input Supply | Accepts 3V–30V input; requires local 2.2µF ceramic bypass capacitor placed adjacent to pin. |
| SHDN | Enable/Disable Control | Logic-high (>1.2V) enables operation; logic-low (<0.4V) disables switch and reduces quiescent current to <1µA. |
| CTRL | Current Setpoint Input | 0–1V analog input scaling LED current threshold from 0 to 100mV; ties to VREF for full-scale operation. |
| PWM | Digital Dimming Input | Active-low signal disabling main switch and preserving VC charge state for fast recovery during 5000:1 dimming. |
| SYNC | External Clock Input | Accepts 20% faster external clock than RT-set frequency to synchronize switching and reduce beat frequencies. |
| FB | Voltage Feedback Input | Regulates output voltage to 1.01V threshold; used for overvoltage protection and CV mode in boost/buck-boost configurations. |
| RT | Frequency Programming | Resistor-to-GND sets oscillator frequency; open circuit prohibited; 16.9kΩ yields 1MHz nominal operation. |
| ISP / ISN | High-Side Current Sense | Differential inputs measuring voltage across external sense resistor; rail-to-rail operation supports wide LED string voltage range. |
| TG | PMOS Gate Driver Output | Inverted PWM signal driving external PMOS between VISP and (VISP – 7V); 7V clamp protects gate oxide. |
| TGEN | TG Enable Input | Logic-high (>1.5V) activates TG driver; internal 40kΩ pull-down ensures disable if left floating. |
| VREF | 2.0V Reference Output | Stable 2.0V ±2% reference sourcing up to 100µA; used for CTRL biasing and external resistor-divider setting. |
| VC | Error Amplifier Output | gm amplifier output (550µS) requiring RC compensation network for loop stability and transient response tuning. |
| SS | Soft-Start Control | Capacitor-to-GND controls startup ramp rate; 0.1µF typical value limits inrush current and output overshoot. |
| GND | Ground / Exposed Pad | Thermal and electrical ground connection; exposed pad (Pin 17) must be soldered to PCB ground plane with thermal vias. |
Key Features
| Feature | Design Value |
|---|---|
| Triple-Topology Operation | Configurable as boost, buck, or buck-boost via external component selection-enabling single IC solution across diverse LED voltage requirements. |
| Open LED Protection | Automatic shutdown when ISP–ISN voltage exceeds threshold, preventing unregulated output voltage rise and safeguarding downstream components. |
| Load Dump Tolerance | Withstands 40V nonrepetitive 1-second transients on VIN-meeting ISO 7637-2 Pulse 5a requirements for automotive 12V systems. |
| Integrated PMOS Driver | TG pin drives external PMOS to disconnect LED string during PWM off-time, eliminating output capacitor discharge and enabling true 5000:1 dimming fidelity. |
| Low Shutdown Current | <1µA quiescent draw in shutdown-critical for always-on automotive modules where battery drain must be minimized. |
Applications
| Automotive Headlamp Control | Industrial Display Backlighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) requiring precise, flicker-free dimming and robust operation under 12V battery fluctuations and load-dump events. IC Role / Device Role / Timing Role: Constant-current LED driver regulating 1A–3A strings in buck-boost configuration, with TG-driven PMOS disconnect for rapid PWM response and open-LED fault detection. Use Value: Enables 5000:1 dimming resolution and 150°C junction rating for under-hood placement without derating, reducing BOM count versus discrete solutions. | Use Scenario: High-brightness LCD backlight for medical imaging displays requiring stable luminance across ambient temperature shifts and long operational life. IC Role / Device Role / Timing Role: Boost-mode constant-current source driving 10–20 white LEDs in series, regulated via FB loop for overvoltage protection and ISP/ISN for current accuracy. Use Value: 100mV current sense threshold minimizes I²R losses and heat generation in shunt resistor, improving thermal management and system efficiency. |
| Aerospace Cabin Lighting | Barcode Scanner Illumination |
Use Scenario: Weight- and reliability-critical LED lighting in commercial aircraft cabins, subject to extended temperature cycling and stringent EMI limits. IC Role / Device Role / Timing Role: Buck-mode driver powering distributed LED arrays, leveraging SYNC pin to align switching with avionics master clock and suppress conducted emissions. Use Value: Adjustable 250kHz–2.5MHz frequency allows EMI filtering optimization while maintaining 1.5A switch capability in compact QFN package. | Use Scenario: High-speed barcode scanners requiring microsecond-level LED strobe timing and consistent optical output intensity across varying supply voltages. IC Role / Device Role / Timing Role: Constant-current source in boost topology with CTRL-based analog trim and PWM-triggered strobing, synchronized via SYNC for deterministic timing. Use Value: Dual dimming (5000:1 PWM + 10:1 analog) extends dynamic range beyond standard scanner requirements, supporting multi-spectral illumination modes. |
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 3A switch current, no integrated current sense amplifier; requires external op-amp for current regulation. | Targeted at higher-power LED arrays (>2A) and multi-string configurations; lacks 100mV sense and built-in open-LED protection. | Select when >2A output current or multi-channel independent control is required; not drop-in due to different compensation and sensing architecture. |
| MAX16820ATP+ | Fixed 2MHz switching frequency, 1.2A switch, 200mV current sense threshold, no SYNC or TG pin. | Optimized for cost-sensitive, space-constrained portable lighting; limited to boost-only topology and narrower input range (4.5V–28V). | Choose for simpler, lower-cost boost-only designs where 5000:1 dimming and automotive temp grade are not required. |
Compared with LTC3783EFE#PBF and MAX16820ATP+, the LT3517HUF#PBF uniquely combines triple-topology flexibility, integrated 100mV current sensing, 150°C operation, and PMOS disconnect capability-making it optimal for high-reliability, thermally demanding LED systems requiring both precision dimming and fault resilience.
Availability
LT3517HUF#PBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial display backlighting, aerospace cabin lighting, and barcode scanner illumination requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3517HUF#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3517 product line was designed specifically for high-efficiency, high-reliability LED lighting in harsh environments-emphasizing wide input range, integrated protection features, and flexible topology support for automotive and avionic applications.
FAQ
What is the maximum operating junction temperature for the LT3517HUF#PBF?
The LT3517HUF#PBF is specified for a maximum operating junction temperature of 150°C, with guaranteed performance across –40°C to 150°C. This H-grade qualification makes LT3517HUF#PBF suitable for under-hood automotive applications where ambient temperatures exceed 125°C, unlike the E- and I-grade variants rated only to 125°C.
How does the LT3517HUF#PBF achieve 5000:1 PWM dimming ratio?
The LT3517HUF#PBF achieves 5000:1 true-color PWM dimming by combining fast-switching disable/enable of the main power switch with preservation of the VC pin's charge state during PWM low periods. This eliminates recovery delay, and when paired with an external PMOS driven by the TG pin to disconnect the LED string, it prevents output capacitor discharge-ensuring precise average current control down to 0.02% duty cycle.
Can the LT3517HUF#PBF operate in buck, boost, and buck-boost topologies with the same PCB layout?
No-the LT3517HUF#PBF supports all three topologies but requires distinct external component configurations: buck uses PVIN tied to VIN and SW connected to inductor input; boost uses SW to inductor input and PVIN to LED cathode; buck-boost requires additional flying capacitor and diode routing. The LT3517HUF#PBF pinout remains identical, but board layout must be optimized per topology to manage current paths, grounding, and EMI.
What is the purpose of the TG and TGEN pins on the LT3517HUF#PBF?
The TG pin is a dedicated PMOS gate driver output that delivers an inverted PWM signal referenced to VISP, clamped to VISP – 7V for gate oxide protection. The TGEN pin enables this function: applying >1.5V activates TG, while grounding or leaving it floating (due to internal 40kΩ pull-down) disables it. Together, they enable fast LED string disconnection during PWM off-time-critical for achieving LT3517HUF#PBF's 5000:1 dimming fidelity.
Does the LT3517HUF#PBF require external compensation components on the VC pin?
Yes-the VC pin is the output of the internal transconductance error amplifier (550µS) and requires external RC compensation for loop stability. For most LED applications, a 10nF capacitor from VC to GND suffices; adding a series resistor increases slew rate to improve transient response during fast VIN or CTRL changes. Omitting compensation risks oscillation or poor regulation, especially in buck-boost configurations with high output impedance.
LT3517HUF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- True Color PWM™
- 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:
- 1.5A (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)
LT3517HUF#PBF FAQ
1.How can I place an order for LT3517HUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3517HUF#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 LT3517HUF#PBF reliable?
The price and inventory of LT3517HUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3517HUF#PBF is usually 5 days.
3.What payment methods are accepted for LT3517HUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3517HUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3517HUF#PBF?
LT3517HUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3517HUF#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 LT3517HUF#PBF?
For technical support, including LT3517HUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3517HUF#PBF requirements.
6.How does Aetrix verify that LT3517HUF#PBF is sourced from the original manufacturer or authorized distributors?
All LT3517HUF#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 LT3517HUF#PBF meets industry standards.
7.What is the process for return or replacement of LT3517HUF#PBF?
All LT3517HUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3517HUF#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 LT3517HUF#PBF part is unused and in its original packaging.
Return procedure for LT3517HUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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