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Analog Devices Inc. LT3955EUHE#PBF
- Part No.:
- LT3955EUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3955EUHE#PBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3.5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,893
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Product details
Overview
LT3955EUHE#PBF from Analog Devices (formerly Linear Technology) is a 60V-input, constant-current/constant-voltage DC/DC converter with integrated 80V/3.5A N-channel MOSFET, designed for high-power LED driving in boost, SEPIC, buck-boost, and flyback topologies. It delivers ±3% current regulation and ±2% voltage regulation, supports 3000:1 True Color PWM™ dimming, and operates from –40°C to 125°C junction temperature.
For engineers reviewing the LT3955EUHE#PBF datasheet, LT3955EUHE#PBF pinout, LT3955EUHE#PBF application, or LT3955EUHE#PBF equivalent, this page provides verified technical context, validated pin functions, confirmed thermal and electrical specifications, and real-world application mappings - all grounded in the official Linear Technology/LTC documentation and product marking data.
Technical Context
The LT3955EUHE#PBF implements a fixed-frequency, current-mode control architecture with internal slope compensation, enabling stable operation across wide input (4.5V–60V) and output voltage ranges. Its dual-loop capability allows seamless transition between constant-current (CC) and constant-voltage (CV) regulation via FB and ISP/ISN feedback paths.
It integrates a programmable PWM dimming signal generator (170Hz–390Hz), analog dimming via CTRL (0–1V linear threshold adjustment), and fault protection including open-LED detection (FB–50mV + ISP–ISN <25mV), overcurrent shutdown (ISP–ISN ≥600mV), and FB overvoltage latch-off (FB ≥ VFB+60mV).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 60V - supports automotive battery, industrial 24V/48V rails, and wide-range off-line inputs without pre-regulation. |
| Switch Rating | 80V drain-source, 3.5A continuous - enables high-power LED strings up to 65V at 300mA in boost configuration with margin. |
| Current Regulation Accuracy | ±3% - ensures consistent LED brightness across temperature and unit-to-unit variation without external calibration. |
| PWM Dimming Ratio | 3000:1 True Color PWM™ - preserves color fidelity in high-end lighting by avoiding low-frequency flicker and duty-cycle nonlinearity. |
| Switching Frequency Range | 100kHz to 1MHz - selectable via RT resistor to balance efficiency, EMI, and magnetics size (e.g., 350kHz typical in 20W reference design). |
| Thermal Package | 36-lead 5mm × 6mm QFN with exposed GND/SW pads - achieves θJA = 34°C/W for sustained 20W LED drive without forced air. |
| Shutdown Current | <1µA - enables ultra-low-power standby in battery-powered signage or emergency lighting systems. |
Pinout & Package
LT3955EUHE#PBF is housed in a thermally enhanced 36-lead (5mm × 6mm) plastic QFN package with two exposed pads: Pin 37 (GND) and Pin 38 (SW), both requiring direct soldering to PCB copper planes for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pins 8, 9, 20, 21, Exposed Pad 38) | Drain of internal N-MOSFET | High-current switching node; must be routed with low-inductance, high-copper-area trace tied directly to SW plane. |
| ISP / ISN (Pins 28 / 27) | High-side or low-side current sense inputs | Enable rail-to-rail sensing (0V–80V common-mode); differential voltage sets LED current (e.g., 250mV across RSENSE = full-scale). |
| FB (Pin 25) | Voltage feedback input | Regulates output voltage to 1.25V reference; also triggers open-LED detection when combined with ISP/ISN <25mV. |
| CTRL (Pin 31) | Analog dimming / current threshold control | Linearly adjusts current sense threshold from 20mV to 250mV (0–1V input), enabling precise analog dimming or thermal derating. |
| DIM/SS (Pin 35) | Soft-start and PWM generator programming | Charging current sets PWMOUT duty cycle; capacitor value determines soft-start time and dimming frequency stability. |
| RT (Pin 36) | Frequency adjustment | Resistor to GND programs switching frequency (e.g., 95.3kΩ → 350kHz); critical for EMI compliance and inductor selection. |
| VMODE (Pin 34) | Open-LED / CV-mode status indicator | Open-drain output pulled low when FB drops below VFB–50mV AND ISP–ISN <25mV - signals transition to voltage regulation or fault condition. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 80V/3.5A Power Switch | Eliminates external MOSFET and gate driver, reducing BOM count and layout complexity in high-voltage LED drivers. |
| Rail-to-Rail Current Sense Range (0V–80V) | Supports both high-side and low-side sensing configurations without level-shifting circuitry, simplifying PCB routing and noise immunity. |
| True Color PWM™ Dimming (3000:1) | Preserves LED chromaticity at low dimming levels by eliminating low-frequency artifacts and maintaining precise duty-cycle linearity. |
| Output Short-Circuit Protected Boost | Automatically disables switch and asserts PWMOUT low during ISP–ISN overvoltage (>600mV), protecting LEDs and FETs during load faults. |
| Programmable VIN UVLO with Hysteresis | EN/UVLO pin allows user-defined turn-on/off thresholds (e.g., 12V start, 10.5V shutdown) with 40mV hysteresis to prevent oscillation near brownout. |
| C/10 Indication for Battery Chargers | Enables accurate end-of-charge detection in supercapacitor or LiFePO4 charging applications using ISP–ISN voltage threshold (25mV typical). |
Applications
| Automotive LED Headlamps | Industrial High-Bay Lighting |
|---|---|
|
Use Scenario: Driving 12–24V input, multi-string white LED arrays in vehicle forward lighting with strict thermal and EMI requirements. IC Role / Device Role / Timing Role: Constant-current controller managing boost topology with synchronized PWM dimming for adaptive driving beams. Use Value: ±3% current accuracy maintains consistent lumen output across temperature; 350kHz switching avoids AM radio band interference. |
Use Scenario: Powering 48V-input, 60–100W LED fixtures in warehouse ceilings with long cable runs and ambient temperatures up to 70°C. IC Role / Device Role / Timing Role: Dual-loop CC/CV regulator operating in SEPIC mode to tolerate input dips and regulate string voltage during thermal derating. Use Value: Rail-to-rail ISP/ISN sensing enables low-side sensing on high-voltage strings; exposed SW pad sustains 20W dissipation at 125°C junction. |
| Medical Surgical Lighting | Smart Streetlight Drivers |
|
Use Scenario: Precision dimmable LED modules in OR lights requiring flicker-free, color-stable illumination under DALI or 0–10V control. IC Role / Device Role / Timing Role: Analog + PWM hybrid dimmer using CTRL for coarse adjustment and PWMOUT for fine-grained True Color PWM™. Use Value: 3000:1 dimming range meets IEC 60601-2-41 surgical light standards; VMODE pin reports open-circuit faults to safety controller. |
Use Scenario: Outdoor LED streetlight power supply with surge protection, grid voltage fluctuations (90–305VAC rectified), and remote monitoring. IC Role / Device Role / Timing Role: Constant-current LED driver in buck-boost configuration, interfacing with MCU via VMODE and FB for telemetry and fault logging. Use Value: Open-LED detection (via FB+ISP/ISN logic) enables predictive maintenance alerts; INTVCC LDO powers auxiliary monitoring circuitry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3761EUHE#PBF | Higher 100V input rating, no integrated PWM generator, requires external oscillator; 4.5A switch. | Better suited for >60V input industrial lighting; lacks self-oscillating dimming, needing external PWM source. | Select when input exceeds 60V or when external clock synchronization is mandatory; not drop-in for LT3955EUHE#PBF's DIM/SS-based dimming. |
| LM3409QMH/NOPB | 48V max input, 5A switch, no integrated PWM generator, automotive AEC-Q100 qualified. | Targeted at automotive cabin lighting; lacks C/10 charging function and open-LED reporting via VMODE. | Choose for AEC-Q100-compliant designs where 60V input headroom is unnecessary and functional safety certification is required. |
Compared with LT3955EUHE#PBF, LT3761EUHE#PBF trades integrated dimming for higher input voltage tolerance and LT3955EUHE#PBF offers superior system integration for non-automotive high-brightness LED applications requiring minimal external components and embedded diagnostics.
Availability
LT3955EUHE#PBF is available at Aetrix Electronics and suitable for automotive LED headlamps, industrial high-bay lighting, medical surgical lighting, and smart streetlight drivers requiring stable component supply, long-term lifecycle support, and lead-free compliance.
Supply support for LT3955EUHE#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 and maintains full product support, documentation, and manufacturing continuity for the LT3955 family.
The LT3955 belongs to Linear's high-voltage LED driver product line, engineered specifically for precision constant-current regulation in demanding lighting and power conversion applications where reliability, dimming fidelity, and thermal robustness are critical.
FAQ
What is the maximum LED string voltage supported by the LT3955EUHE#PBF in boost configuration?
The LT3955EUHE#PBF supports LED string voltages up to 65V in its typical 20W boost reference design (VIN = 24V). Its 80V-rated internal switch and rail-to-rail 0V–80V ISP/ISN sensing range allow safe operation with output voltages approaching 75V, provided thermal limits and layout parasitics are managed per the datasheet layout guidelines.
Does the LT3955EUHE#PBF require an external PWM signal generator, or can it self-oscillate?
The LT3955EUHE#PBF can self-oscillate: connecting a capacitor from the PWM pin to GND activates its internal programmable PWM generator, with frequency set by DIM/SS charging current (170Hz–390Hz) and duty ratio controlled by DIM/SS voltage. No external signal generator is needed for basic dimming functionality.
How does the LT3955EUHE#PBF handle open-LED conditions?
The LT3955EUHE#PBF detects open-LED faults when FB falls below VFB–50mV (≈1.205V) while ISP–ISN drops below 25mV. This triggers the VMODE pin to pull low, signaling the fault. Simultaneously, PWMOUT is driven low to disconnect the LED string if an external NMOS is used, preventing unregulated voltage rise.
What is the purpose of the GNDK (Pin 12) on the LT3955EUHE#PBF?
GNDK (Kelvin ground) provides a dedicated low-impedance return path for the internal current-sense amplifier, separate from power ground (PGND). It must be connected directly to the PCB ground plane near the IC to eliminate voltage drop errors in high-accuracy current regulation - critical for maintaining ±3% LED current tolerance.
Can the LT3955EUHE#PBF be used for battery charging applications?
Yes - the LT3955EUHE#PBF supports constant-current/constant-voltage battery and supercapacitor charging. Its C/10 indication (triggered at ISP–ISN ≈25mV) enables precise end-of-charge detection, and FB loop regulation ensures safe voltage termination, as validated in Linear's AN138 application note for LiFePO4 charging.
LT3955EUHE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Flyback, SEPIC, Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 4.5V
- Voltage - Supply (Max):
- 60V
- Voltage - Output:
- -
- Current - Output / Channel:
- 3.5A (Switch)
- Frequency:
- 100kHz ~ 1MHz
- Dimming:
- Analog, PWM
- Applications:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3955EUHE#PBF FAQ
1.How can I place an order for LT3955EUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3955EUHE#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 LT3955EUHE#PBF reliable?
The price and inventory of LT3955EUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3955EUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3955EUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3955EUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3955EUHE#PBF?
LT3955EUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3955EUHE#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 LT3955EUHE#PBF?
For technical support, including LT3955EUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3955EUHE#PBF requirements.
6.How does Aetrix verify that LT3955EUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3955EUHE#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 LT3955EUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3955EUHE#PBF?
All LT3955EUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3955EUHE#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 LT3955EUHE#PBF part is unused and in its original packaging.
Return procedure for LT3955EUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3955EUHE#PBF Tags
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BCR402RE6327HTSA1
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BCR430UXTSA2
Infineon Technologies
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BCR420UE6433HTMA1
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BCR420UE6327HTSA1
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BCR421UE6327HTSA1
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LYT1604D-TL
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HV9910CLG-G
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CL2N8-G
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BCR420UW6-7
Diodes Incorporated
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BCR421UW6-7
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BCR420UFD-7
Diodes Incorporated
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