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Analog Devices Inc. LT3955EUHE#TRPBF
- Part No.:
- LT3955EUHE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3955EUHE#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3.5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,376
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Product details
Overview
LT3955EUHE#TRPBF from Analog Devices (formerly Linear Technology) is a 60V-input, constant-current/constant-voltage DC/DC LED controller with integrated 80V/3.5A N-channel MOSFET, programmable 100kHz–1MHz switching frequency, ±3% current regulation accuracy, and True Color PWM™ dimming up to 3000:1. It drives high-power LEDs in boost, SEPIC, buck-boost, or flyback topologies and supports battery/supercapacitor charging.
For engineers reviewing the LT3955EUHE#TRPBF datasheet, LT3955EUHE#TRPBF pinout, LT3955EUHE#TRPBF application, or LT3955EUHE#TRPBF equivalent, key selection criteria include high-side/low-side current sensing capability (0V–80V common-mode), rail-to-rail ISP/ISN threshold adjustability via CTRL pin (0–1V linear range), open-LED and output short-circuit protection, and thermally enhanced 36-lead 5mm × 6mm QFN package with dual exposed pads (GND and SW).
Technical Context
The LT3955EUHE#TRPBF 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 design simultaneously regulates LED current via ISP/ISN differential sensing and output voltage via FB feedback, with automatic mode transition signaled by VMODE.
It integrates a self-oscillating PWM dimming generator (programmable 4%–96% duty via DIM/SS current), analog dimming via CTRL (0–1V), and fault management including ISP–ISN overcurrent detection (600mV threshold), FB overvoltage shutdown (VFB + 60mV), and thermal shutdown at 165°C. The INTVCC LDO (7.85V, 36mA) powers internal drivers and requires local 1µF ceramic bypassing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 60V - supports automotive battery, industrial 24/48V rails, and wide-range DC supplies without external pre-regulation. |
| Switch Rating | 80V drain-source, 3.5A continuous - enables direct drive of high-Vf LED strings (e.g., 65V @ 300mA) in boost configuration. |
| Current Regulation Accuracy | ±3% - ensures consistent luminance across temperature and unit variation in LED lighting systems. |
| PWM Dimming Ratio | 3000:1 - preserves color fidelity (True Color PWM™) for architectural, medical, and display backlighting. |
| Switching Frequency Range | 100kHz to 1MHz - allows trade-off between efficiency (lower fSW) and component size (higher fSW) using RT resistor. |
| ISP/ISN Common-Mode Range | 0V to 80V - supports high-side sensing in boost/flyback or low-side sensing in buck/SEPIC without level-shifting circuitry. |
| Thermal Package | 36-lead 5mm × 6mm QFN with dual exposed pads (GND and SW) - achieves θJA = 34°C/W for high-power LED driver thermal management. |
Pinout & Package
LT3955EUHE#TRPBF is housed in a thermally enhanced 36-lead plastic QFN (5mm × 6mm), featuring two exposed pads: Pin 37 (GND) and Pin 38 (SW), both requiring solder connection to respective PCB copper planes for optimal thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ISP / ISN (Pins 28 / 27) | High-side or low-side current sense inputs | Differential measurement of LED current via external sense resistor; supports 0V–80V common-mode range and ±3% regulation accuracy. |
| FB (Pin 25) | Voltage feedback input | Regulates output voltage to 1.25V reference; enables CV mode, open-LED detection (VFB – 50mV), and overvoltage shutdown (VFB + 60mV). |
| CTRL (Pin 31) | Analog dimming and current threshold control | Linearly adjusts ISP–ISN current sense threshold from 21mV to 258mV (0–1V input), enabling precise analog dimming and temperature compensation. |
| DIM/SS (Pin 35) | Soft-start and PWM dimming generator control | Programs PWMOUT duty cycle (4%–96%) and soft-start time via external capacitor; internal 12µA pull-up sets dimming frequency. |
| VMODE (Pin 34) | Open-LED / CV-mode status indicator | Open-drain output pulled low when FB > VFB – 50mV AND ISP–ISN < 25mV - signals transition from CC to CV regulation or open-load fault. |
| PWMOUT (Pin 23) | Buffered PWM output | Drives external NMOS disconnect switch or level shifter; toggles low during FB overvoltage or ISP–ISN overcurrent faults for load isolation. |
| SW (Pins 8, 9, 20, 21, 38) | Drain of internal 80V/3.5A N-MOSFET | Primary power switching node; exposed pad (Pin 38) must be soldered to SW copper plane for thermal and low-inductance routing. |
| GND (Pins 4, 24, 37) | Signal and power ground reference | Multiple GND pins and exposed pad (Pin 37) reduce ground impedance and improve noise immunity in high-di/dt LED drive paths. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ dimming | 3000:1 ratio with no color shift - critical for high-CRI LED applications in medical imaging and studio lighting. |
| Configurable topology support | Drives LEDs in boost, SEPIC, Cuk, buck, buck-boost, or flyback - eliminates need for multiple controller families across product lines. |
| Integrated protection suite | Open-LED reporting (VMODE), output short-circuit protected boost, ISP–ISN overcurrent (600mV), FB overvoltage (VFB + 60mV), and thermal shutdown - reduces BOM count and system-level validation effort. |
| Accurate analog dimming | CTRL pin adjusts current sense threshold from 21mV to 258mV with ±3% linearity - enables smooth, flicker-free dimming synchronized with ambient light sensors. |
| Programmable frequency & UVLO | RT pin sets fSW (100kHz–1MHz); EN/UVLO offers adjustable hysteresis via external resistor - optimizes EMI compliance and brown-out resilience. |
Applications
| Automotive Headlamp Driver | Industrial High-Bay Lighting |
|---|---|
|
Use Scenario: Driving 65V, 300mA white LED strings in 12V/24V vehicle electrical systems with cold-crank tolerance down to 4.5V. IC Role / Device Role / Timing Role: Constant-current LED controller with integrated 80V/3.5A switch, operating in boost mode with 350kHz switching frequency and 3000:1 True Color PWM™ dimming. Use Value: Eliminates external high-voltage MOSFET and gate driver; maintains ±3% current accuracy across –40°C to 125°C ambient for consistent lumen output. |
Use Scenario: Powering multi-string 48V LED arrays in warehouse lighting fixtures requiring DALI-compatible analog dimming and surge immunity. IC Role / Device Role / Timing Role: Constant-current regulator with CTRL-based analog dimming and FB-based overvoltage clamping, configured in SEPIC for AC/DC offline compatibility. Use Value: Enables single-chip solution for 0–10V dimming interface and open-circuit LED string detection (VMODE reporting) without auxiliary comparators. |
| Battery & Supercapacitor Charger | Medical Endoscope Illumination |
|
Use Scenario: Charging 24V Li-ion packs or 30V supercapacitors from 12–60V sources with C/10 charge termination and thermal foldback. IC Role / Device Role / Timing Role: Constant-voltage/constant-current charger using FB for voltage regulation and ISP/ISN for current limiting, with C/10 indication via VMODE assertion. Use Value: Replaces dedicated charger ICs; uses same current-sense architecture for accurate charge current control and end-of-charge detection. |
Use Scenario: Driving RGB LED modules in surgical endoscopes requiring flicker-free, color-stable dimming and rapid on/off response for image capture synchronization. IC Role / Device Role / Timing Role: High-speed PWM dimming controller with 180ns minimum on-time, 160ns minimum off-time, and 3000:1 True Color PWM™ for artifact-free video imaging. Use Value: Delivers sub-millisecond dimming transitions and zero color shift across full intensity range - essential for diagnostic-grade illumination fidelity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#TRPBF | Requires external high-side N-MOSFET; no integrated switch; supports higher VIN (100V) but lacks internal PWM generator. | Better suited for ultra-high-voltage (>80V) LED strings or where discrete FET selection is required for thermal partitioning. | Select when system demands >80V output or discrete FET optimization; not drop-in due to missing internal switch and PWMOUT functionality. |
| MAX16834ATP+T | Fixed 500kHz fSW; no DIM/SS programmable PWM generator; lower current limit (2.5A); no VMODE open-LED reporting pin. | Targeted at cost-sensitive, medium-power (<15W) LED drivers where 3000:1 dimming and fault reporting are non-critical. | Choose for simpler, lower-cost designs lacking advanced protection and dimming features; requires external PWM source for >1000:1 dimming. |
Compared with LTC3783EFE#TRPBF and MAX16834ATP+T, the LT3955EUHE#TRPBF uniquely integrates an 80V/3.5A switch, self-oscillating PWM generator, and VMODE fault reporting - reducing component count by ≥4 devices and enabling compact, high-reliability LED driver designs with minimal external circuitry.
Availability
LT3955EUHE#TRPBF is available at Aetrix Electronics and suitable for automotive headlamp systems, industrial high-bay lighting, battery charging circuits, and medical endoscope illumination requiring stable component supply and long-term production continuity.
Supply support for LT3955EUHE#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 (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 LT3955EUHE#TRPBF belongs to Linear's high-voltage LED controller product line, designed specifically for robust, high-efficiency constant-current LED driving in harsh environments - emphasizing thermal resilience, fault coverage, and topology flexibility.
FAQ
What is the maximum LED string voltage supported by the LT3955EUHE#TRPBF in boost configuration?
The LT3955EUHE#TRPBF supports LED string voltages up to 80V in boost mode, constrained by its internal 80V-rated N-channel MOSFET and ISP/ISN input common-mode range of 0V–80V. In the typical 24V input, 65V LED string application (300mA), it delivers 94% efficiency. Exceeding 80V requires external high-side switch or alternative topology like SEPIC.
How does the LT3955EUHE#TRPBF implement open-LED detection?
The LT3955EUHE#TRPBF detects open-LED conditions by monitoring two simultaneous conditions: FB voltage falling below VFB – 50mV (1.205V typical) while ISP–ISN differential drops below 25mV (C/10 threshold). When both occur, the VMODE pin pulls low - providing a dedicated, latchable fault signal usable for system-level diagnostics or safety shutdown.
Can the LT3955EUHE#TRPBF operate without an external PWM signal source?
Yes - the LT3955EUHE#TRPBF includes an integrated PWM dimming signal generator. By connecting a capacitor from the PWM pin to GND and biasing DIM/SS with its internal 12µA current source, it self-oscillates with duty ratio programmable from 4% to 96%. This eliminates need for external microcontroller or timer IC in basic dimming applications.
What is the purpose of the dual exposed pads (Pins 37 and 38) on the LT3955EUHE#TRPBF QFN package?
Pin 37 (exposed pad) is electrically connected to GND and must be soldered to the PCB ground plane for thermal dissipation and low-impedance return path. Pin 38 (exposed pad) connects directly to the SW node and must be soldered to the switch-node copper pour - minimizing parasitic inductance in the high-di/dt power loop and improving efficiency and EMI performance.
Does the LT3955EUHE#TRPBF support battery charging applications with C/10 termination?
Yes - the LT3955EUHE#TRPBF supports C/10 charge termination via its VMODE pin. When ISP–ISN falls below 25mV (typical) while FB remains regulated, VMODE asserts low. This signal can trigger external circuitry to terminate charging, making the LT3955EUHE#TRPBF suitable for Li-ion, lead-acid, and supercapacitor charging with accurate current-limited voltage regulation.
LT3955EUHE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT3955EUHE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3955EUHE#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 LT3955EUHE#TRPBF reliable?
The price and inventory of LT3955EUHE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3955EUHE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3955EUHE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3955EUHE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3955EUHE#TRPBF?
LT3955EUHE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3955EUHE#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 LT3955EUHE#TRPBF?
For technical support, including LT3955EUHE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3955EUHE#TRPBF requirements.
6.How does Aetrix verify that LT3955EUHE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3955EUHE#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 LT3955EUHE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3955EUHE#TRPBF?
All LT3955EUHE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3955EUHE#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 LT3955EUHE#TRPBF part is unused and in its original packaging.
Return procedure for LT3955EUHE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3955EUHE#TRPBF Tags
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