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Analog Devices Inc. LT3755IUD#PBF
- Part No.:
- LT3755IUD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755IUD#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,768
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Product details
Overview
LT3755IUD#PBF from Analog Devices is a constant-frequency, current-mode DC/DC LED controller driving external N-channel MOSFETs in boost, buck, buck-boost, SEPIC, or flyback topologies. It delivers up to 75V output with 4.5V–40V input, 100mV high-side current sense threshold, and 3000:1 PWM dimming. Used in automotive LED headlamps requiring precise constant-current regulation.
For engineers reviewing the LT3755IUD#PBF datasheet, LT3755IUD#PBF pinout, LT3755IUD#PBF application, or LT3755IUD#PBF equivalent, key selection factors include high-side current sensing architecture, AEC-Q100 qualification, programmable 100kHz–1MHz switching frequency, open LED protection via FB-based fault detection, and thermal shutdown at 165°C.
Technical Context
The LT3755IUD#PBF implements fixed-frequency current-mode control with internal 7.15V INTVCC regulator powering gate driver and logic. Its error amplifier (VC) regulates either LED current via ISP/ISN differential sensing or output voltage via FB pin referenced to 1.25V nominal.
High-side current sensing enables topology flexibility and avoids ground loop issues. The CTRL pin adjusts current sense threshold from 0V to 1.1V, enabling analog dimming or temperature compensation; PWM input supports true-color PWM dimming with 3000:1 ratio and fast disconnect via PWMOUT-driven NMOS.
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 LED strings in headlamp and signage applications. |
| Current Sense Threshold | 100mV (typical) at ISP–ISN - enables accurate, low-loss high-side current sensing with minimal power dissipation. |
| Switching Frequency Range | 100kHz to 1MHz - adjustable via RT resistor for optimizing efficiency, EMI, or magnetic component size. |
| Operating Junction Temp | –40°C to +125°C - I-grade rating ensures reliability in under-hood automotive environments. |
| Shutdown Current | <1µA - enables ultra-low-power standby in always-on lighting systems. |
| AEC-Q100 Qualification | Qualified - meets automotive stress test requirements for temperature, humidity, and lifetime reliability. |
Pinout & Package
LT3755IUD#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 performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 14) | Main input supply connection | Accepts 4.5V–40V; requires local 0.22µF+ ceramic bypass capacitor. |
| GATE (Pin 16) | N-channel MOSFET gate driver output | Sinks/sourcing to INTVCC or GND; drives external power switch with 35ns rise/fall time. |
| SENSE (Pin 15) | Low-side switch current sense input | Kelvin-connected to source of external NMOS; monitors peak switch current for current-mode control. |
| ISP / ISN (Pins 4 / 3) | High-side LED string current sense inputs | Differential pair measuring voltage across sense resistor; supports 2.9V–75V common-mode range. |
| FB (Pin 2) | Voltage feedback input | Regulates output voltage to 1.25V reference; enables open-LED detection when FB drops below VFB –50mV. |
| CTRL (Pin 6) | Analog dimming and current threshold control | Adjusts ISP–ISN threshold from 0V to 1.1V; enables temperature-compensated current regulation. |
| PWM (Pin 8) | Digital dimming enable input | Active-low signal; provides 3000:1 true-color PWM dimming with synchronized PWMOUT for load disconnect. |
| OPENLED (Pin 9) | Open-LED fault indicator | Open-collector output asserting pull-down when FB falls below VFB –50mV (LT3755/LT3755-2 only). |
| RT (Pin 11) | Frequency programming input | Resistor-to-GND sets oscillator frequency from 100kHz to 1MHz per manufacturer curve. |
| SHDN/UVLO (Pin 12) | Shutdown and undervoltage lockout | 1.22V falling threshold with programmable hysteresis; disables IC and resets soft-start on undervoltage. |
| VC (Pin 5) | Error amplifier output | High-impedance during PWM low; stores demand state; requires RC compensation network for loop stability. |
| INTVCC (Pin 13) | Internal regulated supply | 7.15V LDO output powering gate driver and logic; requires 4.7µF ceramic bypass capacitor. |
| VREF (Pin 7) | 2.0V reference output | Stable 2.0V source for CTRL biasing or external temperature compensation networks; supplies ≤100µA. |
| SS (Pin 10) | Soft-start timing input | 10µA internal current charges external capacitor; controls startup ramp rate and prevents inrush. |
| PWMOUT (Pin 1) | Buffered PWM output | Drives NMOS disconnect switch; toggles low if FB exceeds VFB +60mV for overvoltage LED protection. |
| Exposed Pad (Pin 17) | Thermal and electrical ground | Mandatory solder connection to PCB ground plane for thermal dissipation and noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| High-side current sensing | Enables flexible topology selection (boost/buck/buck-boost/SEPIC/flyback) without compromising ground-referenced control. |
| True-color PWM dimming | 3000:1 dimming ratio preserves LED color fidelity across full brightness range-critical for automotive adaptive lighting. |
| Programmable open-LED detection | FB-based fault detection (VFB –50mV threshold) provides reliable load-disconnect signaling without additional circuitry. |
| Integrated 7.15V gate driver supply | Eliminates need for external bias rail; supports robust NMOS drive with <35ns edge speeds and 34mA current limit. |
| Thermal shutdown protection | 165°C junction limit with automatic recovery prevents permanent damage during transient overloads or poor heatsinking. |
Applications
| Automotive LED Headlamps | Battery-Powered LED Lighting |
|---|---|
Use Scenario: High-brightness adaptive front-lighting system (AFS) in passenger vehicles operating across –40°C to +125°C ambient. IC Role / Device Role / Timing Role: Constant-current LED controller regulating 1A+ strings in boost configuration with dynamic dimming and fault reporting. Use Value: AEC-Q100 qualification and wide input range ensure operation during cold cranking (6V) and load dump (40V), while 3000:1 PWM maintains beam pattern integrity. | Use Scenario: Portable emergency lighting or industrial handheld tools powered by 12V lead-acid or Li-ion batteries. IC Role / Device Role / Timing Role: Buck-mode LED driver delivering stable current despite battery voltage sag from 12.8V down to 9V. Use Value: 4.5V minimum VIN and <1µA shutdown current extend runtime; high-side sensing avoids ground contamination in shared-battery systems. |
| Architectural LED Signage | Industrial Machine Vision Lighting |
Use Scenario: Outdoor digital signage requiring uniform brightness across 20+ LED modules under variable solar heating and humidity. IC Role / Device Role / Timing Role: Constant-voltage + constant-current hybrid controller using FB and ISP/ISN loops to maintain lumen output and prevent thermal runaway. Use Value: Programmable CTRL-based current scaling compensates for LED forward-voltage drift with temperature; 75V output supports long series strings reducing wiring complexity. | Use Scenario: High-speed inspection systems needing strobed illumination synchronized to camera exposure with microsecond timing precision. IC Role / Device Role / Timing Role: Fast-response LED driver using PWMOUT to trigger external NMOS disconnect switch for sub-10µs LED turn-off. Use Value: PWMOUT's 50mV VOL and INTVCC-referenced VOH ensure clean, fast switching; 170ns minimum off-time enables high-frequency strobing up to 500kHz. |
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 5V bias supply instead of 7.15V; no OPENLED pin. | Targeted at lower-power, fixed-frequency designs where programmability and fault reporting are secondary. | Select when board space is constrained and frequency optimization is unnecessary; verify compatibility with existing 5V bias architecture. |
| LM3410XSDX/NOPB | Single-stage buck-only controller; max 32V output; no high-side sensing; 2.5V–24V input; no AEC-Q100 rating. | Designed for cost-sensitive consumer LED lighting, not automotive or high-reliability industrial use. | Choose only for non-automotive, low-output-voltage (<32V), buck-only applications where qualification and topology flexibility are not required. |
Compared with LTC3783EFE#PBF and LM3410XSDX/NOPB, the LT3755IUD#PBF offers broader topology support, AEC-Q100 compliance, and programmable frequency-making it uniquely suited for demanding automotive and industrial LED systems where reliability, flexibility, and fault diagnostics are critical.
Availability
LT3755IUD#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 and long-term production continuity.
Supply support for LT3755IUD#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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3755 product line was designed specifically for high-reliability, high-efficiency LED driver applications-emphasizing wide input range, precise current regulation, topology flexibility, and automotive-grade robustness.
FAQ
What is the maximum output voltage supported by the LT3755IUD#PBF?
The LT3755IUD#PBF supports output voltages up to 75V, enabling it to drive long LED strings in automotive headlamps and architectural lighting. This capability is achieved through high-voltage ISP/ISN inputs rated to 75V and robust internal gate driver design. The actual achievable output depends on external component selection-including inductor saturation current, diode reverse voltage, and MOSFET breakdown rating-but the controller itself is specified for 75V operation.
Does the LT3755IUD#PBF support both constant-current and constant-voltage regulation?
Yes, the LT3755IUD#PBF supports dual-loop regulation: constant-current via ISP/ISN differential sensing and constant-voltage via the FB pin referenced to 1.25V. When both loops are active, the IC prioritizes current regulation unless the FB voltage exceeds its threshold, at which point voltage loop takes precedence-enabling safe open-LED protection and hybrid CV/CC operation in applications like LED signage with thermal derating.
How does the OPENLED pin function on the LT3755IUD#PBF?
The OPENLED pin on the LT3755IUD#PBF is an open-collector output that asserts a pull-down when the FB voltage falls below VFB –50mV (typical), indicating an open LED condition. It requires an external pull-up resistor (<1mA). During PWM low periods, the state is latched; upon next PWM high transition, OPENLED updates. This feature eliminates need for external comparators in fault-monitoring circuits and is specific to LT3755 and LT3755-2 variants-not LT3755-1.
What is the purpose of the CTRL pin on the LT3755IUD#PBF?
The CTRL pin on the LT3755IUD#PBF adjusts the ISP–ISN current sense threshold from 0V to 1.1V: below 1V, threshold scales linearly as (VCTRL – 100mV)/10RLED; above 1.2V, it holds at full-scale 100mV. This enables analog dimming, temperature compensation (e.g., using NTC with VREF), or dynamic current scaling. Leaving CTRL unconnected is prohibited-tie to VREF or GND depending on desired operating mode.
Is the LT3755IUD#PBF pin-compatible with other variants like LT3755-1 or LT3755-2?
No, the LT3755IUD#PBF is not pin-compatible with LT3755-1 or LT3755-2. While all share identical QFN-16 packaging and core pinout, Pin 9 serves as OPENLED on LT3755IUD#PBF but as SYNC on LT3755-1, and as enhanced OPENLED on LT3755-2. Using LT3755IUD#PBF in a layout designed for LT3755-1 would leave SYNC unconnected and disable synchronization, while substituting LT3755-2 may cause unintended behavior due to updated fault-latching logic.
LT3755IUD#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#PBF FAQ
1.How can I place an order for LT3755IUD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755IUD#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#PBF reliable?
The price and inventory of LT3755IUD#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#PBF is usually 5 days.
3.What payment methods are accepted for LT3755IUD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755IUD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755IUD#PBF?
LT3755IUD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755IUD#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#PBF?
For technical support, including LT3755IUD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755IUD#PBF requirements.
6.How does Aetrix verify that LT3755IUD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3755IUD#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#PBF meets industry standards.
7.What is the process for return or replacement of LT3755IUD#PBF?
All LT3755IUD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755IUD#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#PBF part is unused and in its original packaging.
Return procedure for LT3755IUD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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