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Analog Devices Inc. LT3755EUD-2#PBF
- Part No.:
- LT3755EUD-2#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755EUD-2#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,173
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Product details
Overview
LT3755EUD-2#PBF from Analog Devices is a constant-frequency, current-mode DC/DC LED controller optimized for high-current automotive and industrial LED drivers. It drives an external N-channel MOSFET, supports 4.5V–40V input, delivers up to 75V output, features 100mV high-side current sensing, and enables true-color PWM dimming up to 3000:1 in boost/buck/buck-boost topologies.
For engineers reviewing the LT3755EUD-2#PBF datasheet, LT3755EUD-2#PBF pinout, LT3755EUD-2#PBF application, or LT3755EUD-2#PBF equivalent, key selection criteria include its AEC-Q100 qualification, open LED protection with dedicated OPENLED pin, programmable 100kHz–1MHz switching frequency via RT resistor, and dual-loop (constant-current + constant-voltage) regulation capability for robust LED system design.
Technical Context
The LT3755EUD-2#PBF implements a fixed-frequency current-mode control architecture with internal 7.15V INTVCC regulator powering the gate driver and logic. Its high-side ISP/ISN current sense interface operates up to 75V common-mode voltage and provides 100mV full-scale threshold with CTRL-adjustable scaling (0–1.1V), enabling precise LED current regulation across wide temperature and supply ranges.
Unlike the LT3755-1 (SYNC-capable) and base LT3755, the LT3755-2 variant integrates an improved open LED status pin (OPENLED) with latched fault reporting during PWM idle states and re-assertion behavior after overvoltage recovery-critical for automotive headlamp safety compliance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 40V - supports 12V/24V automotive battery rails with cold-crank margin. |
| Output Voltage Capability | Up to 75V - enables driving long LED strings in headlamp and signage applications. |
| Current Sense Threshold | 100mV (typical) at ISP–ISN - enables accurate, low-loss high-side sensing with 0.1Ω shunt. |
| Switching Frequency Range | 100kHz to 1MHz - adjustable via RT pin resistor for EMI optimization or magnetics size reduction. |
| Dimming Ratio | 3000:1 PWM - ensures flicker-free, high-fidelity color rendering in dynamic lighting systems. |
| Operating Junction Temp | –40°C to +125°C - qualified per AEC-Q100 Grade E for under-hood automotive use. |
| Package | 16-lead 3mm × 3mm QFN with exposed pad - thermally enhanced for high-power LED driver PCB layouts. |
Pinout & Package
LT3755EUD-2#PBF uses 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/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PWMOUT (Pin 1) | Buffered PWM output | Drives NMOS disconnect switch; toggles low on FB overvoltage (>VFB + 60mV) to isolate LED load. |
| FB (Pin 2) | Voltage feedback input | Regulates to 1.25V nominal; enables CV mode and open-LED detection (pulls OPENLED when FB < VFB – 50mV). |
| ISN (Pin 3) | Negative current sense input | High-side current sense return; supports >2.9V common-mode for buck-boost configurations. |
| ISP (Pin 4) | Positive current sense input | High-side current sense high terminal; short-circuit detection active when ISN < 3V. |
| VC (Pin 5) | Error amplifier output | Integrates ISP–ISN error; high-impedance during PWM low to retain state for next cycle. |
| CTRL (Pin 6) | Current threshold adjust | Scales ISP–ISN threshold from 0–100mV linearly (0–1.1V); clamps at full scale above 1.2V. |
| VREF (Pin 7) | 2.0V reference output | Stable 2.0V source (±2%) for CTRL divider or temperature compensation networks. |
| PWM (Pin 8) | Digital dimming input | Active-low enable; disables switching, idles oscillator, and forces GATE/PWMOUT low. |
| OPENLED (Pin 9) | Open LED fault indicator | Open-collector pull-down asserted when FB < VFB – 50mV; latched during PWM idle (LT3755-2 specific). |
| SS (Pin 10) | Soft-start control | 10µA pull-up to 2.5V rail; external capacitor sets ramp time; reset by UVLO or thermal fault. |
| RT (Pin 11) | Frequency programming | Resistor-to-GND sets oscillator frequency (100kΩ → ~375kHz); no internal pull-up. |
| SHDN/UVLO (Pin 12) | Shutdown & input monitoring | 1.22V falling threshold with programmable hysteresis; sub-µA shutdown IQ. |
| INTVCC (Pin 13) | Internal LDO output | 7.15V regulated supply (±150mV); powers gate driver; requires 4.7µF local ceramic bypass. |
| VIN (Pin 14) | Main power input | 4.5V–40V input; must be bypassed with ≥0.22µF ceramic capacitor near pin. |
| SENSE (Pin 15) | Low-side current sense | Kelvin-connected to FET source; monitors switch current for slope-compensated current-mode control. |
| GATE (Pin 16) | MOSFET gate driver | Drives external N-channel FET between INTVCC and GND; fast rise/fall (<35ns into 3.3nF). |
| Exposed Pad (Pin 17) | Thermal & electrical ground | Must be soldered to PCB ground plane; serves as current sense return path for SENSE pin. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q100 qualification | Grade E (–40°C to +125°C) ensures reliability for automotive headlamp and interior lighting systems. |
| High-side current sensing | Supports ISP/ISN inputs up to 75V common-mode voltage - enables flexible topology selection (boost, buck, SEPIC, flyback). |
| Improved OPENLED pin | Latched fault reporting during PWM idle and automatic re-assertion after overvoltage recovery - meets ASIL-B diagnostic coverage requirements. |
| Dual-loop regulation | Simultaneous constant-current (via ISP/ISN/CTRL) and constant-voltage (via FB) control - prevents LED overvoltage during open-circuit faults. |
| Programmable soft-start | External capacitor on SS pin controls startup dI/dt and inrush current - eliminates input rail sag and stress on input capacitors. |
Applications
| Automotive LED Headlamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Driving 50W white LED arrays in adaptive front-lighting systems (AFS) with dynamic beam shaping. IC Role / Device Role / Timing Role: Constant-current LED controller with open-LED fault detection and PWM dimming interface for ECU-synchronized light modulation. Use Value: AEC-Q100 qualification and latched OPENLED reporting ensure functional safety compliance (ISO 26262) without external supervision circuitry. | Use Scenario: Powering multi-string 100W+ LED fixtures in warehouse and factory environments with 24V/48V DC distribution. IC Role / Device Role / Timing Role: High-efficiency DC/DC controller supporting buck-boost topology to maintain regulation across wide input voltage swings (e.g., 20–40V). Use Value: 75V output capability and 100mV current sense threshold enable high-current, low-loss operation with minimal thermal derating. |
| Architectural LED Signage | Battery-Powered Emergency Lighting |
Use Scenario: Controlling RGB LED modules in outdoor digital billboards requiring precise color consistency and 3000:1 dimming depth. IC Role / Device Role / Timing Role: Dual-loop controller delivering stable current regulation while preventing overvoltage during string failure or partial disconnect. Use Value: Independent FB and ISP/ISN loops allow simultaneous brightness control and fault containment - eliminating cascading failures across parallel LED strings. | Use Scenario: LED driver in portable emergency lights powered by 12V sealed lead-acid or Li-ion packs with deep discharge tolerance. IC Role / Device Role / Timing Role: Wide-input (4.5V–40V) controller with <1µA shutdown current and programmable UVLO hysteresis for battery state-of-charge management. Use Value: Sub-µA shutdown IQ extends standby runtime; undervoltage lockout prevents deep discharge damage to rechargeable batteries. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3756EUD-2#PBF | Higher 60V ISP/ISN common-mode rating; identical pinout and feature set; rated for –40°C to +125°C. | Targeted at higher-output-voltage LED drivers where ISP/ISN node exceeds 48V but remains below 60V. | Select LT3756EUD-2#PBF only if ISP/ISN voltage exceeds 48V in your topology; otherwise LT3755EUD-2#PBF offers optimal cost/performance balance. |
| LM3410XSDX/NOPB | Single-stage boost-only controller; no high-side current sense; max 40V output; no OPENLED or FB overvoltage protection. | Cost-sensitive, lower-power (<15W) LED applications without fault diagnostics or multi-topology flexibility. | Choose LM3410XSDX/NOPB only for simple boost LED drivers with fixed output and no safety-critical fault reporting needs. |
Compared with LT3756EUD-2#PBF, LT3755EUD-2#PBF offers identical AEC-Q100 qualification and OPENLED functionality at lower ISP/ISN voltage rating (75V vs 60V), while LM3410XSDX/NOPB lacks high-side sensing, dual-loop regulation, and automotive qualification - making it unsuitable for safety-critical or multi-topology designs.
Availability
LT3755EUD-2#PBF is available at Aetrix Electronics and suitable for automotive LED headlamps, industrial high-bay lighting, and architectural signage requiring stable component supply, AEC-Q100 compliance, and high-reliability thermal performance.
Supply support for LT3755EUD-2#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 power management semiconductors, serving automotive, industrial, communications, and healthcare markets.
The LT3755 family was designed specifically for high-power, high-reliability LED driver applications demanding precise current regulation, robust fault protection, and AEC-Q100 qualification - especially in automotive lighting systems.
FAQ
What is the key functional difference between LT3755EUD-2#PBF and the base LT3755EUD#PBF?
The LT3755EUD-2#PBF includes an improved OPENLED pin implementation that latches the open-LED fault condition during PWM idle states and automatically re-asserts the signal after FB recovers from overvoltage events. This behavior enhances diagnostic reliability in automotive lighting systems where intermittent faults must be captured and reported consistently. The base LT3755EUD#PBF does not provide latched reporting or automatic re-assertion.
Can LT3755EUD-2#PBF operate in buck configuration with input voltage higher than output voltage?
Yes, LT3755EUD-2#PBF supports buck topology when VIN exceeds VOUT. Its high-side current sensing architecture (ISP/ISN) and ground-referenced FB pin enable stable constant-current regulation in buck mode. The controller maintains 100mV current sense threshold accuracy and full protection features-including open-LED detection and overvoltage shutdown-even in buck operation.
What is the maximum recommended switching frequency for LT3755EUD-2#PBF in a thermally constrained layout?
The LT3755EUD-2#PBF supports up to 1MHz switching frequency, but in thermally constrained layouts using the 3mm × 3mm QFN package, Analog Devices recommends limiting frequency to ≤500kHz. This balances gate drive losses, INTVCC loading (IINTVCC = QG × fOSC), and thermal rise-especially when driving high-QG MOSFETs or operating near 125°C junction temperature.
How does the CTRL pin affect LED current regulation in LT3755EUD-2#PBF?
The CTRL pin sets the ISP–ISN current sense threshold from 0mV to 100mV linearly over 0–1.1V input, enabling analog dimming or temperature compensation. For VCTRL > 1.2V, the threshold is fixed at 100mV. In LT3755EUD-2#PBF, this directly scales the regulated LED current ILED = (VCTRL – 100mV)/(10 × RLED) for VCTRL ≤ 1V, providing precise, temperature-stable current control independent of PWM duty cycle.
Is LT3755EUD-2#PBF compatible with external synchronization signals?
No, LT3755EUD-2#PBF does not support external synchronization. The SYNC pin is reserved for the LT3755-1 variant only. On LT3755EUD-2#PBF, Pin 9 is designated as OPENLED (not SYNC), and no internal circuitry exists to accept or process external clock signals. Frequency adjustment must be performed exclusively via the RT pin resistor.
LT3755EUD-2#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-2#PBF FAQ
1.How can I place an order for LT3755EUD-2#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755EUD-2#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-2#PBF reliable?
The price and inventory of LT3755EUD-2#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-2#PBF is usually 5 days.
3.What payment methods are accepted for LT3755EUD-2#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755EUD-2#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755EUD-2#PBF?
LT3755EUD-2#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755EUD-2#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-2#PBF?
For technical support, including LT3755EUD-2#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755EUD-2#PBF requirements.
6.How does Aetrix verify that LT3755EUD-2#PBF is sourced from the original manufacturer or authorized distributors?
All LT3755EUD-2#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-2#PBF meets industry standards.
7.What is the process for return or replacement of LT3755EUD-2#PBF?
All LT3755EUD-2#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755EUD-2#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-2#PBF part is unused and in its original packaging.
Return procedure for LT3755EUD-2#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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