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Analog Devices Inc. LT3755EUD-1#PBF
- Part No.:
- LT3755EUD-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755EUD-1#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:722
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Product details
Overview
LT3755EUD-1#PBF from Analog Devices is a constant-frequency, current-mode DC/DC LED controller optimized for high-side current sensing in boost, buck, buck-boost, SEPIC, and flyback topologies. It drives an external N-channel MOSFET with a 7.15V regulated gate supply, supports 4.5V–40V input, delivers up to 75V output, and enables true-color PWM dimming up to 3000:1 - used in automotive LED headlamps and industrial high-power lighting systems.
For engineers reviewing the LT3755EUD-1#PBF datasheet, LT3755EUD-1#PBF pinout, LT3755EUD-1#PBF application, or LT3755EUD-1#PBF equivalent, key selection criteria include its frequency synchronization capability (LT3755-1 variant), 100mV high-side current sense threshold, open LED protection via FB monitoring, and AEC-Q100 qualification for automotive-grade reliability.
Technical Context
The LT3755EUD-1#PBF implements a fixed-frequency current-mode control architecture with internal slope compensation, enabling stable regulation across wide VIN (4.5V–40V) and VOUT (up to 75V) ranges. Its SYNC pin accepts external clock signals for precise switching frequency alignment - a feature exclusive to the -1 variant and absent in standard LT3755 and LT3755-2 parts.
It integrates dual feedback loops: one for constant-current regulation via ISP/ISN differential sensing (100mV full-scale threshold), and another for constant-voltage regulation via FB (1.25V reference). The CTRL pin linearly adjusts current threshold from 0V to 1V, while PWM provides digital dimming control with buffered PWMOUT output for NMOS load disconnect.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 40V - supports 12V/24V automotive battery rails and industrial DC supplies without pre-regulation. |
| Output Voltage Capability | Up to 75V - enables driving long LED strings (e.g., 20× white LEDs @ 3.5V) in boost configuration. |
| Switching Frequency Range | 100kHz to 1MHz - adjustable via RT resistor; synchronized externally on LT3755EUD-1#PBF via SYNC pin. |
| Current Sense Threshold | 100mV (typical) at ISP–ISN - enables accurate high-side LED current regulation with minimal power loss in sense resistor. |
| FB Regulation Voltage | 1.25V (nominal) - ground-referenced voltage loop reference for constant-voltage operation or open-LED detection. |
| Shutdown Current | <1µA - ensures ultra-low quiescent draw during vehicle ignition-off states. |
| Operating Junction Temp | –40°C to +125°C - qualified per AEC-Q100 Grade E for under-hood automotive environments. |
Pinout & Package
LT3755EUD-1#PBF is housed in a thermally enhanced 16-lead (3mm × 3mm) plastic QFN package with exposed pad (Pin 17) soldered to PCB ground for thermal and electrical integrity. Pin numbering follows standard QFN top-view layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PWMOUT (Pin 1) | Buffered PWM output driver | Drives NMOS disconnect switch; toggles low during FB overvoltage (>VFB + 60mV) to isolate LED load. |
| FB (Pin 2) | Voltage feedback input | Ground-referenced 1.25V regulation point; triggers OPENLED pull-down when < VFB – 50mV (open LED fault). |
| ISN (Pin 3) | Negative current sense input | High-side current sense return; enables short-circuit detection when ISN < 3V and ISP–ISN > 150mV. |
| ISP (Pin 4) | Positive current sense input | High-side current sense high terminal; bias current varies with CTRL voltage per datasheet TPCs. |
| VC (Pin 5) | Error amplifier output | Transconductance amplifier output; stabilizes loop with RC network; high-impedance during PWM low. |
| CTRL (Pin 6) | Current threshold adjustment | Sets ISP–ISN threshold from 0V to 1V (linear), then clamps at 100mV above 1.2V - enables analog dimming. |
| VREF (Pin 7) | 2.0V reference output | Stable 2.0V rail (±2%) sourcing ≤100µA - used to bias CTRL divider or temperature compensation networks. |
| PWM (Pin 8) | Digital dimming enable | Active-high control; disables switching, idles oscillator, and forces GATE/PWMOUT low when low. |
| SYNC (Pin 9) | External clock synchronization input | Replaces OPENLED function on LT3755-1 variants; accepts logic-level clock for frequency alignment (not present on LT3755/LT3755-2). |
| SS (Pin 10) | Soft-start timing capacitor | 10µA internal pull-up to 2.5V rail; sets startup ramp time with external capacitor; reset by UVLO or thermal fault. |
| RT (Pin 11) | Frequency programming resistor | Resistor-to-GND sets switching frequency (100kHz–1MHz); RT = 100kΩ yields ~1MHz, RT = 10kΩ yields ~100kHz. |
| SHDN/UVLO (Pin 12) | Shutdown & undervoltage lockout | 1.22V falling threshold with programmable hysteresis; pulls down 2.1µA to set hysteresis via external divider. |
| INTVCC (Pin 13) | Internal LDO output (7.15V) | Regulated supply for gate driver, PWMOUT, and internal logic; requires 4.7µF ceramic bypass close to pin. |
| VIN (Pin 14) | Main input supply | Accepts 4.5V–40V; powers INTVCC LDO and internal circuitry; must be bypassed with ≥0.22µF ceramic capacitor. |
| SENSE (Pin 15) | Low-side switch current sense | Kelvin-connected to source of external N-MOSFET; monitors switch current for current-mode control and limit. |
| GATE (Pin 16) | N-MOSFET gate driver | Drives external FET between INTVCC and GND; turns off during shutdown, fault, or idle states. |
| Exposed Pad (Pin 17) | Thermal & electrical ground | Must be soldered to PCB ground plane; serves as primary thermal path and low-impedance return for SENSE resistor. |
Key Features
| Feature | Design Value |
|---|---|
| Frequency synchronization | SYNC pin enables precise external clock alignment - eliminates beat frequencies and EMI peaks in multi-controller systems. |
| True-color PWM dimming | 3000:1 dimming ratio achieved via clean PWM edge control and fast GATE response (35ns rise/fall), preserving LED color fidelity. |
| High-side current sensing | ISP/ISN inputs support flexible topology selection (boost/buck/buck-boost/SEPIC/flyback) without ground-loop interference. |
| Open LED fault detection | FB-based monitoring asserts OPENLED (or uses SYNC pin on -1 variant) to signal open-circuit conditions before overvoltage damage. |
| AEC-Q100 qualification | Grade E (–40°C to +125°C) qualification ensures reliability in automotive headlamp, DRL, and interior lighting applications. |
| Programmable soft-start | SS pin with external capacitor prevents inrush current and output overshoot during power-up in high-power LED drivers. |
Applications
| Automotive LED Headlamps | Battery-Powered High-Brightness Lighting |
|---|---|
|
Use Scenario: 50W white LED headlamp module powered from 12V/24V vehicle battery with dynamic voltage transients. IC Role / Device Role / Timing Role: Constant-current controller regulating LED string current via high-side ISP/ISN sensing; synchronizes switching to reduce EMI in safety-critical lighting. Use Value: Enables AEC-Q100-compliant, flicker-free illumination with 3000:1 dimming for adaptive driving beams and DRL integration. |
Use Scenario: Portable stage lighting or emergency beacon using Li-ion battery (8–36V) to drive multiple high-flux LED strings. IC Role / Device Role / Timing Role: Buck-boost LED controller maintaining regulated current despite battery voltage sag; uses CTRL pin for analog brightness scaling. Use Value: Delivers consistent lumen output across full battery discharge curve while minimizing heat generation in compact enclosures. |
| Industrial Machine Vision Illumination | Architectural LED Signage Power Supply |
|
Use Scenario: High-speed strobed lighting for factory floor inspection systems requiring microsecond-level timing precision. IC Role / Device Role / Timing Role: PWM-synchronized LED driver with <170ns minimum off-time and fast GATE response for sub-millisecond flash control. Use Value: Eliminates motion blur in high-frame-rate imaging by enabling precise, repeatable LED on/off transitions without color shift. |
Use Scenario: Constant-current power supply for outdoor RGB LED signage operating in wide ambient temperature ranges (–40°C to +85°C). IC Role / Device Role / Timing Role: Boost-mode LED controller with open-LED protection and thermal derating via VC loop; operates from 24VDC distributed bus. Use Value: Ensures fail-safe operation and uniform brightness across thousands of LEDs, reducing maintenance in inaccessible installations. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3755EUD#PBF | Lacks SYNC pin; OPENLED function active on Pin 9; no external frequency synchronization capability. | Suitable for standalone LED drivers where EMI co-location is not critical and fixed-frequency operation suffices. | Select when system-level clock alignment is unnecessary and cost-sensitive BOM optimization is prioritized. |
| LT3755EUD-2#PBF | Features improved OPENLED status pin behavior (re-asserts after overvoltage clears); no SYNC functionality. | Preferred for safety-critical open-load detection in medical or aerospace lighting where fault reporting integrity is paramount. | Choose when robust, re-triggerable open-LED reporting is required and synchronization is not needed. |
Compared with LT3755EUD#PBF and LT3755EUD-2#PBF, the LT3755EUD-1#PBF uniquely provides external clock synchronization - essential for noise-sensitive multi-channel LED systems - while retaining AEC-Q100 qualification and identical pinout, enabling drop-in replacement where SYNC is unused.
Availability
LT3755EUD-1#PBF is available at Aetrix Electronics and suitable for automotive LED headlamps, battery-powered portable lighting, and industrial machine vision systems requiring stable component supply, AEC-Q100 compliance, and precise frequency control.
Supply support for LT3755EUD-1#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving automotive, industrial, communications, and healthcare markets.
The LT3755 family was designed specifically for high-efficiency, high-reliability LED current regulation in demanding environments - emphasizing topology flexibility, fault protection, and automotive-grade robustness.
FAQ
What distinguishes LT3755EUD-1#PBF from the base LT3755EUD#PBF?
The LT3755EUD-1#PBF replaces the OPENLED function on Pin 9 with a SYNC input for external clock synchronization - enabling precise frequency alignment in multi-controller systems. All other electrical characteristics, pinout, package, and AEC-Q100 qualification remain identical to LT3755EUD#PBF, allowing mechanical compatibility where SYNC is unused.
Does LT3755EUD-1#PBF support both constant-current and constant-voltage regulation?
Yes, LT3755EUD-1#PBF supports dual-loop regulation: constant-current via ISP/ISN differential sensing (100mV threshold) and constant-voltage via FB pin (1.25V reference). The two loops interact - FB regulates output voltage while ISP/ISN limits peak LED current - enabling safe operation in open-circuit or overvoltage fault conditions.
What is the purpose of the CTRL pin on LT3755EUD-1#PBF?
The CTRL pin on LT3755EUD-1#PBF adjusts the ISP–ISN current sense threshold linearly from 0V to 1V (e.g., 0.5V sets 50mV threshold), enabling analog dimming or temperature-compensated current regulation. Above 1.2V, the threshold clamps at 100mV full-scale - ensuring predictable current limiting independent of CTRL voltage drift.
Can LT3755EUD-1#PBF drive LEDs in buck configuration?
Yes, LT3755EUD-1#PBF supports buck, boost, buck-boost, SEPIC, and flyback topologies due to its high-side current sensing architecture (ISP/ISN). In buck mode, it regulates LED current referenced to input voltage - ideal for 24V industrial lighting where output voltage must stay below VIN.
Is LT3755EUD-1#PBF suitable for automotive applications?
Yes, LT3755EUD-1#PBF is AEC-Q100 qualified (Grade E, –40°C to +125°C) and features integrated protections including open-LED detection, short-circuit sensing, thermal shutdown, and undervoltage lockout - making it suitable for automotive LED headlamps, DRLs, and interior lighting per ISO 16750-2 requirements.
LT3755EUD-1#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Controller
- Topology:
- Flyback, SEPIC, Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- No
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 4.5V
- Voltage - Supply (Max):
- 40V
- Voltage - Output:
- -
- Current - Output / Channel:
- -
- Frequency:
- 100kHz ~ 1MHz
- Dimming:
- Analog, PWM
- Applications:
- -
- Operating Temperature:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LT3755EUD-1#PBF FAQ
1.How can I place an order for LT3755EUD-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755EUD-1#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 LT3755EUD-1#PBF reliable?
The price and inventory of LT3755EUD-1#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3755EUD-1#PBF is usually 5 days.
3.What payment methods are accepted for LT3755EUD-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755EUD-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755EUD-1#PBF?
LT3755EUD-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755EUD-1#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 LT3755EUD-1#PBF?
For technical support, including LT3755EUD-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755EUD-1#PBF requirements.
6.How does Aetrix verify that LT3755EUD-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT3755EUD-1#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 LT3755EUD-1#PBF meets industry standards.
7.What is the process for return or replacement of LT3755EUD-1#PBF?
All LT3755EUD-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755EUD-1#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 LT3755EUD-1#PBF part is unused and in its original packaging.
Return procedure for LT3755EUD-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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