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Analog Devices Inc. LT3755IUD-2#PBF
- Part No.:
- LT3755IUD-2#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755IUD-2#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:462
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Product details
Overview
LT3755IUD-2#PBF from Analog Devices is a constant-frequency, current-mode DC/DC LED controller optimized for high-current automotive and industrial lighting. 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 LT3755IUD-2#PBF datasheet, LT3755IUD-2#PBF pinout, LT3755IUD-2#PBF application, or LT3755IUD-2#PBF equivalent, key selection criteria include its AEC-Q100 qualification, open-LED protection with dedicated OPENLED pin, programmable frequency (100kHz–1MHz), 1.25V FB regulation, and thermally enhanced 3mm × 3mm QFN package with exposed ground pad.
Technical Context
The LT3755IUD-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 current sense inputs (ISP/ISN) enable flexible topology support-boost, buck, buck-boost, SEPIC, or flyback-without requiring ground-referenced LED strings.
It integrates dual-loop regulation: LED current is controlled via ISP–ISN differential voltage (programmable from 0 to 100mV using CTRL), while FB provides constant-voltage feedback referenced to 1.25V. The LT3755-2 variant adds improved open-LED status reporting on the OPENLED pin with latched fault behavior during PWM idle states.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 40V - supports wide automotive battery range including cold-crank and load-dump conditions. |
| Output Voltage Capability | Up to 75V - enables driving long series strings of high-brightness white LEDs. |
| Current Sense Threshold | 100mV (typical) at ISP–ISN - sets precise LED current with minimal power loss in sense resistor. |
| Switching Frequency Range | 100kHz to 1MHz - adjustable via RT resistor to balance efficiency, EMI, and magnetics size. |
| FB Regulation Voltage | 1.25V (nominal) - stable reference for constant-voltage loop or overvoltage protection. |
| CTRL Pin Adjustment Range | 0V to 1.1V - linearly scales current threshold from 0mV to full-scale 100mV for analog dimming. |
| Shutdown Current | <1µA - enables ultra-low-power standby in always-on automotive systems. |
| Operating Junction Temp | –40°C to +125°C - qualified for under-hood and industrial ambient environments. |
Pinout & Package
LT3755IUD-2#PBF uses a thermally enhanced 16-lead (3mm × 3mm) plastic QFN package with exposed ground pad (Pin 17), rated for –40°C to +125°C operation. The exposed pad must be soldered to PCB ground for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PWMOUT (Pin 1) | Buffered PWM output | Drives external NMOS disconnect switch; toggles low during FB overvoltage (>VFB + 60mV) to protect LEDs. |
| FB (Pin 2) | Voltage feedback input | Ground-referenced node for CV regulation or open-LED detection; regulates to 1.25V nominal. |
| ISN (Pin 3) | Negative current sense input | High-side current sense return; enables short-circuit detection when ISN < 3V. |
| ISP (Pin 4) | Positive current sense input | High-side current sense high side; bias current varies with CTRL voltage per datasheet curve. |
| VC (Pin 5) | Error amplifier output | Integrates error signal for loop stability; high-impedance during PWM low to retain state. |
| CTRL (Pin 6) | Current threshold control | Sets ISP–ISN regulation point: 100mV when VCTRL > 1.2V; linear scaling below 1V. |
| 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-high enable; controls switching and resets VC state; internal pull-down. |
| OPENLED (Pin 9) | Open-LED fault indicator | Open-collector output asserted when FB < VFB – 50mV; latched during PWM idle (LT3755-2 feature). |
| SS (Pin 10) | Soft-start control | 10µA pull-up to 2.5V rail; external capacitor sets startup ramp time and prevents inrush. |
| RT (Pin 11) | Frequency programming | Resistor-to-GND sets oscillator frequency; 100kΩ = ~375kHz per typical curve. |
| SHDN/UVLO (Pin 12) | Enable & undervoltage lockout | 1.22V falling threshold with programmable hysteresis; disables IC below VIN min. |
| INTVCC (Pin 13) | Internal LDO output | 7.15V regulated supply for gate driver and logic; 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; clamped during fault/shutdown. |
| Exposed Pad (Pin 17) | Thermal & electrical ground | Must be soldered to PCB ground plane for thermal dissipation and current sense return path. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q100 qualification | Validated for automotive applications including temperature cycling, vibration, and ESD robustness. |
| High-side current sensing | Enables all topologies (boost/buck/buck-boost/SEPIC/flyback) without grounding LED cathode. |
| True-color PWM dimming | 3000:1 ratio achieved via clean, jitter-free PWMOUT synchronization with internal oscillator. |
| Programmable open-LED response | OPENLED pin asserts when FB drops below VFB – 50mV and remains latched during PWM off (LT3755-2). |
| Integrated 7.15V INTVCC LDO | Eliminates need for external bias supply; powers gate driver and logic with built-in current limit (34mA typ). |
| Adjustable frequency with RT pin | 100kHz–1MHz range allows optimization of magnetics size, efficiency, and EMI compliance. |
Applications
| Automotive LED Headlamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: 50W white LED headlamp driver in passenger vehicle front lighting module. IC Role / Device Role / Timing Role: Constant-current controller regulating 1.5A through 12-series white LEDs in boost configuration. Use Value: AEC-Q100 qualification ensures reliability under thermal shock and vibration; OPENLED latching enables fault logging during intermittent lamp disconnection. | Use Scenario: High-efficiency 100W LED fixture for warehouse ceiling mounting with 0–10V dimming interface. IC Role / Device Role / Timing Role: Buck-mode LED driver with analog dimming via CTRL pin and digital override via PWM input. Use Value: 100mV current sense threshold minimizes I²R loss in shunt resistor; 40V max input accommodates 24V/48V industrial supplies. |
| Battery-Powered Emergency Lighting | UV-C LED Disinfection Systems |
Use Scenario: Portable emergency exit sign powered by 12V sealed lead-acid battery with low-quiescent operation. IC Role / Device Role / Timing Role: Boost converter maintaining constant LED current across 10.5V–14.4V battery range. Use Value: <1µA shutdown current extends battery life; programmable UVLO prevents deep discharge damage. | Use Scenario: Pulsed UV-C LED array (275nm) for surface sterilization requiring precise current control and thermal derating. IC Role / Device Role / Timing Role: Constant-current source with temperature-compensated CTRL network using VREF output. Use Value: High-side sensing avoids ground loop interference in high-noise disinfection enclosures; 75V output supports multi-string UV LED arrays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#PBF | Fixed 500kHz frequency; no RT pin; integrated gate driver with higher peak current (2A); no OPENLED pin. | Targeted at compact, fixed-frequency designs where layout simplicity outweighs programmability needs. | Choose LTC3783EFE#PBF when board space is constrained and frequency flexibility is not required. |
| LM3410XMF/NOPB | Single-stage boost-only controller; lower max input (24V); no high-side sensing; no CTRL analog dimming. | Suitable for low-power (<10W), cost-sensitive consumer LED lighting with simple boost topology. | Choose LM3410XMF/NOPB only for non-automotive, low-voltage, single-topology applications lacking fault reporting needs. |
Compared with LTC3783EFE#PBF and LM3410XMF/NOPB, LT3755IUD-2#PBF uniquely combines AEC-Q100 qualification, programmable frequency, high-side current sensing, and latched OPENLED reporting-making it the only option qualified for automotive headlamp duty cycles and robust industrial fault diagnostics.
Availability
LT3755IUD-2#PBF is available at Aetrix Electronics and suitable for automotive LED headlamps, industrial high-bay lighting, and battery-powered emergency signage requiring stable component supply, long-term lifecycle support, and AEC-Q100 compliance.
Supply support for LT3755IUD-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 digital signal processing semiconductors, serving precision instrumentation, industrial automation, and automotive safety markets.
The LT3755 product line was designed specifically for high-reliability, high-power LED lighting systems demanding accurate current regulation, topology flexibility, and automotive-grade robustness.
FAQ
What is the key functional difference between LT3755IUD-2#PBF and the standard LT3755IUD#PBF?
The LT3755IUD-2#PBF includes an improved OPENLED pin implementation that latches the open-LED fault condition during PWM idle periods and reasserts it upon PWM reactivation-unlike the base LT3755IUD#PBF, which deasserts OPENLED when PWM goes low. This behavior enhances diagnostic reliability in pulsed-dimming automotive systems. All other electrical specifications and pinouts remain identical between the two variants.
Can LT3755IUD-2#PBF operate in buck configuration with high-side current sensing?
Yes, LT3755IUD-2#PBF supports buck topology using high-side current sensing via ISP and ISN pins-enabling the LED string to remain grounded while maintaining accurate current regulation. This eliminates ground-loop issues common in multi-string industrial fixtures. The controller's architecture inherently supports buck, boost, buck-boost, SEPIC, and flyback configurations without external level-shifting circuitry.
What is the minimum recommended capacitor value for the INTVCC pin on LT3755IUD-2#PBF?
The minimum recommended capacitor for the INTVCC pin on LT3755IUD-2#PBF is 4.7µF, using a 10V-rated X7R or X5R ceramic capacitor placed as close as possible to the pin. This value ensures stable LDO operation and supplies peak gate drive current during switching transitions. Lower values may cause INTVCC droop, leading to inconsistent gate drive or premature UVLO shutdown under heavy load.
How does the CTRL pin on LT3755IUD-2#PBF affect LED current regulation?
The CTRL pin on LT3755IUD-2#PBF directly programs the ISP–ISN current sense threshold: for VCTRL > 1.2V, the threshold is fixed at 100mV; for 0V < VCTRL < 1V, it scales linearly from 0mV to 100mV; and between 1V–1.2V, it transitions smoothly to full scale. This enables precise analog dimming or temperature-based current derating using the internal 2.0V VREF output as a stable reference for the CTRL divider network.
Is LT3755IUD-2#PBF compatible with synchronous rectification in boost mode?
No, LT3755IUD-2#PBF is not designed for synchronous rectification. It drives only a single external N-channel MOSFET via the GATE pin and relies on a diode for the freewheeling path in boost mode. Synchronous operation would require a second gate driver and complementary timing control-neither of which is implemented in the LT3755IUD-2#PBF architecture. For synchronous boost, consider the LT8390 or LT8705 families instead.
LT3755IUD-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:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LT3755IUD-2#PBF FAQ
1.How can I place an order for LT3755IUD-2#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755IUD-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 LT3755IUD-2#PBF reliable?
The price and inventory of LT3755IUD-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 LT3755IUD-2#PBF is usually 5 days.
3.What payment methods are accepted for LT3755IUD-2#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755IUD-2#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755IUD-2#PBF?
LT3755IUD-2#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755IUD-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 LT3755IUD-2#PBF?
For technical support, including LT3755IUD-2#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755IUD-2#PBF requirements.
6.How does Aetrix verify that LT3755IUD-2#PBF is sourced from the original manufacturer or authorized distributors?
All LT3755IUD-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 LT3755IUD-2#PBF meets industry standards.
7.What is the process for return or replacement of LT3755IUD-2#PBF?
All LT3755IUD-2#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755IUD-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 LT3755IUD-2#PBF part is unused and in its original packaging.
Return procedure for LT3755IUD-2#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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