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Analog Devices Inc. LT3517HFE#PBF
- Part No.:
- LT3517HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3517HFE#PBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,505
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Product details
Overview
LT3517HFE#PBF from Analog Devices is a constant-current/constant-voltage DC/DC LED driver IC with an internal 1.5A, 45V power switch, programmable 250kHz–2.5MHz switching frequency, 100mV high-side current sense threshold, and support for boost/buck/buck-boost topologies. It delivers precise LED current regulation in automotive lighting and display backlighting applications requiring robust thermal performance.
For engineers reviewing the LT3517HFE#PBF datasheet, LT3517HFE#PBF pinout, LT3517HFE#PBF application, or LT3517HFE#PBF equivalent, key selection considerations include its –40°C to 150°C operating junction temperature range, 5000:1 true-color PWM dimming capability, 10:1 analog dimming via CTRL pin, open-LED protection, and TSSOP-16 package compatibility with industrial-grade thermal requirements.
Technical Context
The LT3517HFE#PBF implements dual-loop regulation using a current-mode architecture with independent voltage (FB) and current (ISP/ISN) feedback paths, enabling seamless transition between constant-current and constant-voltage modes. Its internal 1.5A/45V DMOS switch supports wide-input operation (3V–30V), transient tolerance up to 40V, and gate drive for external PMOS disconnect via TG pin.
Switching frequency is set by an external RT resistor or synchronized to an external clock via SYNC pin, with internal oscillator range of 250kHz–2.5MHz. The CTRL pin modulates the current-sense threshold from 0V to 1V (scaling LED current linearly), while PWM input enables high-ratio digital dimming with stored VC node state for fast recovery.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temp Range | –40°C to 150°C junction temperature - enables use in under-hood automotive and high-ambient industrial LED systems without derating. |
| Internal Switch Rating | 1.5A continuous, 45V breakdown - supports high-brightness LED strings with up to ~30W output in buck-boost configurations. |
| Current Sense Threshold | 100mV ±3% - minimizes power loss in sense resistor and improves accuracy over temperature vs. higher-voltage thresholds. |
| PWM Dimming Ratio | 5000:1 - achieves flicker-free, high-fidelity color rendering in display backlighting without visible steps. |
| Input Voltage Range | 3V to 30V continuous, 40V transient - accommodates 12V/24V automotive rails and handles load-dump events per ISO 7637-2. |
| Switching Frequency Range | 250kHz to 2.5MHz - allows optimization for EMI (low-freq) or compactness (high-freq) using single RT resistor or SYNC input. |
| Shutdown Current | <1µA - preserves battery life in always-on vehicle lighting modules during sleep mode. |
Pinout & Package
LT3517HFE#PBF uses a 16-lead plastic TSSOP package (JEDEC MO-153, 4.4mm × 5.0mm × 1.2mm height) with exposed pad not connected internally; thermal management relies on PCB copper area under pin 17 (GND).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Main input supply rail | Accepts 3V–30V DC; requires local 2.2µF ceramic bypass capacitor to suppress high-frequency switching noise. |
| SHDN | Enable/disable control | Logic-high ≥1.2V enables operation; logic-low ≤0.4V disables switch and reduces quiescent current to <1µA. |
| CTRL | Analog current setpoint | 0V–1V input scales LED current linearly (0–100%); tied to VREF for full-scale 100mV sense threshold. |
| PWM | Digital dimming input | Active-low signal disables switching and holds VC node charge for sub-2µs recovery at 2MHz fSW. |
| SYNC | External clock input | Accepts 100kHz–3MHz CMOS clock; RT resistor must be selected for 20% lower free-running frequency. |
| FB | Voltage loop feedback | Regulates to 1.01V threshold; used for overvoltage protection and constant-voltage mode in boost configurations. |
| SS | Soft-start timing | 0.1µF capacitor sets ramp time to limit inrush current and prevent output overshoot at startup. |
| RT | Oscillator frequency set | Resistor to GND programs fSW from 250kHz (91.5kΩ) to 2.5MHz (4.03kΩ); must not be left floating. |
| SW | Power switch drain | Connects to inductor/diode node; trace must be minimized to reduce EMI and voltage ringing. |
| TG | PMOS gate driver output | Drives external PMOS high-side switch with 7V clamp; enables LED string disconnect during PWM off-time. |
| ISP / ISN | High-side current sense inputs | Differential pair referenced to VISP; 100mV full-scale threshold enables accurate, low-loss current measurement. |
| TGEN | PMOS driver enable | Logic-high ≥1.5V activates TG output; internal 40kΩ pull-down ensures safe default-off state. |
| VREF | 2.0V precision reference | Supplies up to 100µA; used to bias CTRL, PWM, and external resistive dividers for stable voltage setting. |
| VC | Error amplifier output | Transconductance amplifier output; compensated externally with RC network for loop stability. |
| GND | Signal and power ground | Pin 17 (exposed pad) is GND; must be soldered to large PCB ground plane for thermal and EMI performance. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ dimming | 5000:1 ratio with stored VC state ensures no color shift or brightness discontinuity during rapid dimming transitions. |
| Integrated PMOS gate driver | TG output with 7V clamp and TGEN enable allows clean LED string disconnection during PWM off-time, preventing output capacitor discharge. |
| Wide-input transient tolerance | Withstands 40V/1s transients per ISO 7637-2 - eliminates need for external TVS in automotive 24V systems. |
| Open-LED fault protection | Automatic shutdown when ISP–ISN voltage exceeds threshold - prevents overvoltage damage to LED string and downstream circuitry. |
| Adjustable frequency synchronization | RT + SYNC dual-mode frequency control enables deterministic EMI reduction in noise-sensitive environments like infotainment displays. |
Applications
| Automotive Headlamp Control | Industrial Display Backlighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) with dynamic beam shaping using multiple LED zones driven from 12V/24V battery rail. IC Role / Device Role / Timing Role: Constant-current LED driver regulating individual LED strings in buck-boost topology with PWM dimming synchronized to camera frame rate. Use Value: –40°C to 150°C rating ensures reliable operation near engine compartment; 5000:1 dimming enables smooth glare-free transitions between low/high beam modes. | Use Scenario: High-brightness LCD backlight for medical imaging monitors requiring uniform luminance and zero flicker across 1000:1 contrast ratio. IC Role / Device Role / Timing Role: Boost-mode LED driver powering parallel LED strings with FB-based overvoltage protection and CTRL-based fine current trimming. Use Value: 100mV current sense minimizes heat in sense resistor; 2.5MHz max switching frequency allows ultra-compact 0402 inductor and capacitor layout. |
| Aerospace Cabin Lighting | Barcode Scanner Illumination |
Use Scenario: Redundant LED lighting module for passenger cabin with MIL-STD-704 compliant input and thermal derating above 85°C ambient. IC Role / Device Role / Timing Role: Buck-mode driver with SHDN-controlled sequencing and TG-driven PMOS disconnect for fail-safe current isolation. Use Value: H-grade 150°C junction rating meets DO-160E thermal requirements; <1µA shutdown current extends emergency battery runtime. | Use Scenario: Pulsed high-intensity illumination source for handheld barcode scanners requiring microsecond-level LED turn-on/off timing. IC Role / Device Role / Timing Role: Synchronized buck-boost driver with 2MHz switching and PWM input aligned to image sensor trigger for precise exposure control. Use Value: Sub-2µs PWM recovery time enables >500fps scanning; open-LED detection prevents false triggers during LED failure. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3517IFE#PBF | Same functionality and pinout, but rated for –40°C to 125°C junction temperature. | Suitable for commercial/industrial environments without extended thermal stress; lower cost than H-grade. | Select when ambient temperature remains below 105°C and automotive qualification is not required. |
| LT3517HUF#PBF | Identical electrical specs and thermal rating, but in 4mm × 4mm QFN package with exposed thermal pad. | Better thermal performance (θJA = 36°C/W vs. 40°C/W) and smaller footprint; requires different PCB layout. | Choose for space-constrained designs needing superior heat dissipation, such as embedded projector modules. |
Compared with LT3517IFE#PBF, the LT3517HFE#PBF provides 25°C higher maximum junction temperature for sustained operation in hot environments, while LT3517HUF#PBF offers improved thermal resistance and reduced board area at the cost of rework complexity for QFN assembly.
Availability
LT3517HFE#PBF is available at Aetrix Electronics and suitable for automotive lighting, industrial display backlighting, and aerospace cabin illumination requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3517HFE#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 precision instrumentation, industrial automation, and automotive markets.
The LT3517 product line was designed specifically for high-reliability LED driving in harsh environments, combining integrated power switching, dual-loop regulation, and automotive-grade thermal and transient robustness.
FAQ
What is the maximum allowable input voltage for continuous operation of the LT3517HFE#PBF?
The LT3517HFE#PBF supports continuous input voltage operation from 3V to 30V. It tolerates nonrepetitive 40V transients for up to one second, making it suitable for automotive 24V systems subject to load-dump conditions per ISO 7637-2. Exceeding 30V continuously risks exceeding thermal limits, especially at high ambient temperatures.
How does the LT3517HFE#PBF achieve 5000:1 PWM dimming ratio?
The LT3517HFE#PBF achieves 5000:1 true-color PWM dimming by combining fast-switching capability (up to 2.5MHz), stored VC node charge during PWM low periods, and precise timing alignment between SYNC and PWM edges. For example, at 2MHz switching frequency, the minimum 2µs pulse width yields a 10ms/2µs = 5000:1 ratio - all while maintaining consistent LED color point across dimming levels.
Can the LT3517HFE#PBF operate in buck, boost, and buck-boost topologies without external component changes?
Yes, the LT3517HFE#PBF supports all three topologies using the same IC, but external component selection (inductor, diode, sense resistor, feedback divider) must match the chosen configuration. The internal current-mode controller and dual-loop regulation automatically adapt to each topology's voltage/current relationships, as verified in Figures TA02a (buck), TA03a (boost), and TA04a (buck-boost) of the LT3517HFE#PBF datasheet.
What is the purpose of the TG and TGEN pins on the LT3517HFE#PBF?
The TG pin is a dedicated PMOS gate driver output that provides an inverted PWM signal with 7V clamping, enabling high-side LED string disconnect. The TGEN pin enables or disables the TG driver - tying TGEN ≥1.5V activates TG, while grounding it disables the output. This combination allows active current-loop interruption during PWM off-time, preventing output capacitor discharge and improving dimming fidelity in the LT3517HFE#PBF.
Does the LT3517HFE#PBF include overtemperature protection?
The LT3517HFE#PBF includes thermal shutdown that disables switching when junction temperature exceeds approximately 165°C. However, this is a safety mechanism - not a thermal regulation feature. Continuous operation above the rated 150°C maximum junction temperature (as specified for the H-grade) will degrade reliability. Proper PCB thermal design using the exposed pad and thermal vias is required to maintain safe operation within the LT3517HFE#PBF's specified range.
LT3517HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- True Color PWM™
- 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:
- 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-TSSOP-EP
LT3517HFE#PBF FAQ
1.How can I place an order for LT3517HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3517HFE#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 LT3517HFE#PBF reliable?
The price and inventory of LT3517HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3517HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3517HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3517HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3517HFE#PBF?
LT3517HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3517HFE#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 LT3517HFE#PBF?
For technical support, including LT3517HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3517HFE#PBF requirements.
6.How does Aetrix verify that LT3517HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3517HFE#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 LT3517HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3517HFE#PBF?
All LT3517HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3517HFE#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 LT3517HFE#PBF part is unused and in its original packaging.
Return procedure for LT3517HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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