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Analog Devices Inc. LT3755IUD#TRPBF
- Part No.:
- LT3755IUD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755IUD#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT3755IUD#TRPBF 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, supports 4.5V–40V input, provides 100mV high-side current sensing, enables 3000:1 PWM dimming, and features AEC-Q100 qualification for automotive headlamp drivers.
For engineers reviewing the LT3755IUD#TRPBF datasheet, LT3755IUD#TRPBF pinout, LT3755IUD#TRPBF application, or LT3755IUD#TRPBF equivalent, key selection criteria include high-side current sense architecture, programmable 100kHz–1MHz switching frequency, open LED protection via FB threshold monitoring, and thermal-enhanced 3mm × 3mm QFN package with exposed ground pad.
Technical Context
The LT3755IUD#TRPBF 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 voltage or output voltage via FB pin referenced to 1.25V.
High-side current sensing enables topology flexibility and avoids ground loop interference; the CTRL pin adjusts current threshold from 0V to 1.1V, scaling V(ISP–ISN) from 0mV to 100mV. Open LED detection activates when FB falls below VFB – 50mV (typ), asserting OPENLED pull-down.
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 single-string or multi-string high-brightness LED arrays without cascading stages. |
| Current Sense Threshold | 100mV (typ) 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 magnetic component size. |
| Dimming Ratio | 3000:1 true-color PWM - preserves LED chromaticity across full brightness range for automotive lighting compliance. |
| Operating Junction Temp | –40°C to +125°C - qualified per AEC-Q100 Grade I for under-hood and headlamp applications. |
| Package | 16-lead 3mm × 3mm QFN with exposed GND pad - enables high-power thermal dissipation in compact layouts. |
Pinout & Package
LT3755IUD#TRPBF uses a thermally enhanced 16-lead plastic QFN (3mm × 3mm) with exposed ground pad (Pin 17), requiring soldering to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PWMOUT (Pin 1) | Buffered PWM output | Drives NMOS disconnect switch; toggles low during FB overvoltage (>VFB + 60mV) to isolate LED load. |
| FB (Pin 2) | Voltage feedback input | Regulates output voltage to 1.25V; triggers OPENLED pull-down if < 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 input; bias current varies with CTRL voltage for accurate gain control. |
| VC (Pin 5) | Error amplifier output | Integrates ISP–ISN vs CTRL error; high-impedance during PWM low to retain state for next cycle. |
| CTRL (Pin 6) | Current threshold adjust | Scales V(ISP–ISN) threshold linearly (0–1V) then clamps at 100mV (>1.2V); enables analog dimming. |
| VREF (Pin 7) | 2.0V reference output | Stable 2.0V source (±2%) for CTRL divider or temperature compensation networks; supplies ≤100µA. |
| PWM (Pin 8) | Digital dimming input | Active-low shutdown; disables oscillator, forces GATE/PWMOUT low, and resets soft-start on falling edge. |
| OPENLED (Pin 9) | Open LED status output | Open-collector pull-down asserted when FB < VFB – 50mV; requires external <1mA pull-up. |
| SS (Pin 10) | Soft-start control | 10µA internal 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 yields ~375kHz per datasheet curve. |
| SHDN/UVLO (Pin 12) | Enable & undervoltage detect | 1.22V falling threshold with programmable hysteresis; sub-µA bias above threshold; pulls down at 2.1µA below. |
| INTVCC (Pin 13) | Internal LDO output | 7.15V regulated supply (±150mV) for gate driver; requires 4.7µF local ceramic bypass. |
| VIN (Pin 14) | Main input supply | Accepts 4.5V–40V; 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) | NMOS gate driver | Drives external FET gate between INTVCC and GND; forced low during shutdown/fault/idle. |
| Exposed Pad (Pin 17) | Thermal & electrical GND | Must be soldered to PCB ground plane; serves as current sense return path and thermal conduction path. |
Key Features
| Feature | Design Value |
|---|---|
| High-side current sensing | Enables topology agnosticism (boost/buck/buck-boost/SEPIC/flyback) without compromising ground-referenced control. |
| Programmable 100kHz–1MHz frequency | Optimizes magnetics size, efficiency, and EMI filtering while maintaining stable current-mode operation. |
| 3000:1 true-color PWM dimming | Maintains LED spectral consistency across full dimming range-critical for automotive adaptive driving beam systems. |
| AEC-Q100 Grade I qualification | Validated for automotive ambient temperatures (–40°C to +125°C junction), meeting reliability and lifetime requirements. |
| Integrated open LED and short-circuit protection | Monitors FB for open load and ISP–ISN differential for short-circuit, independently disabling GATE within one cycle. |
Applications
| Automotive LED Headlamps | Battery-Powered LED Lighting |
|---|---|
Use Scenario: High-intensity front lighting in passenger vehicles with adaptive beam shaping and dynamic leveling. IC Role / Device Role / Timing Role: Constant-current LED controller managing 50W+ white LED strings in boost configuration with real-time thermal derating. Use Value: AEC-Q100 qualification ensures reliability under vibration, thermal cycling, and load dump; 3000:1 PWM dimming enables precise DRL and matrix beam control. | Use Scenario: Portable medical devices, emergency signage, or handheld inspection tools powered by Li-ion or 12V sealed lead-acid batteries. IC Role / Device Role / Timing Role: Wide-input buck-boost LED driver sustaining consistent luminance across battery discharge (10V–40V). Use Value: 4.5V minimum VIN enables operation down to nearly depleted cells; low shutdown IQ (<1µA) extends runtime in standby. |
| Industrial Machine Vision Lighting | Architectural LED Retrofit Drivers |
Use Scenario: High-CRI, strobed illumination for automated optical inspection (AOI) systems requiring microsecond-level timing precision. IC Role / Device Role / Timing Role: Fast-response current controller synchronizing LED flash with camera exposure via PWM input with <100ns jitter. Use Value: Fixed-frequency current mode ensures deterministic timing; OPENLED status enables real-time fault logging during production line operation. | Use Scenario: Retrofitting legacy AC fixtures with DC-powered LED modules using existing 12–48V DC distribution rails. IC Role / Device Role / Timing Role: Constant-voltage regulator (via FB) combined with constant-current regulation (via ISP/ISN) for hybrid CV/CC LED loads. Use Value: Dual-loop capability allows seamless transition between CV mode (for driver ICs) and CC mode (for bare LEDs); 75V output supports long series strings. |
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 programmable RT; lacks OPENLED pin; supports only boost/buck-boost. | Targeted at simpler, cost-sensitive industrial LED drivers without automotive qualification or topology flexibility. | Select when fixed frequency suffices and AEC-Q100 is not required; verify absence of OPENLED does not impact system fault reporting. |
| LM3423MH/NOPB | Lower max output voltage (60V); no CTRL-based analog dimming; integrated gate driver rated for 1.5A peak (vs LT3755's external FET drive). | Designed for mid-power LED drivers (≤30W); optimized for thermal performance in MSOP-10, not QFN. | Choose for lower-power, space-constrained designs where 60V output ceiling and lack of analog dimming are acceptable trade-offs. |
Compared with LTC3783EFE#PBF and LM3423MH/NOPB, LT3755IUD#TRPBF offers broader topology support, AEC-Q100 qualification, programmable frequency, and dual-loop CV/CC regulation-making it uniquely suited for high-reliability, high-flexibility automotive and industrial LED systems.
Availability
LT3755IUD#TRPBF 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 high-side current sensing architecture.
Supply support for LT3755IUD#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 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-efficiency, high-reliability LED current regulation in demanding environments-including automotive front lighting-where topology flexibility, wide input range, and robust fault protection are essential.
FAQ
What is the maximum output voltage supported by the LT3755IUD#TRPBF?
The LT3755IUD#TRPBF supports output voltages up to 75V, enabling direct drive of multi-LED series strings in boost, buck-boost, or SEPIC configurations without intermediate voltage conversion stages. This rating applies across its full operating temperature range and is validated under typical load and layout conditions specified in the datasheet.
Does the LT3755IUD#TRPBF support both constant-current and constant-voltage regulation?
Yes, the LT3755IUD#TRPBF supports dual-loop regulation: constant-current via ISP/ISN differential sensing and constant-voltage via the FB pin referenced to 1.25V. The two loops interact to prevent overvoltage during open-LED events and ensure stable operation in hybrid LED-driver architectures.
How does the OPENLED pin function on the LT3755IUD#TRPBF?
The OPENLED pin on the LT3755IUD#TRPBF is an open-collector output that asserts a pull-down when FB falls below VFB – 50mV (typical), indicating an open LED string. It requires an external pull-up current <1mA and latches status during PWM low periods-providing reliable fault signaling in automotive and industrial lighting systems.
What package type and thermal characteristics apply to the LT3755IUD#TRPBF?
The LT3755IUD#TRPBF uses a 16-lead 3mm × 3mm plastic QFN with exposed ground pad (Pin 17). Its thermal resistance is θJA = 68°C/W and θJC = 4.2°C/W. The exposed pad must be soldered to the PCB ground plane to achieve rated power dissipation and junction temperature limits.
Can the LT3755IUD#TRPBF be synchronized to an external clock?
No-the LT3755IUD#TRPBF variant does not include SYNC functionality. That feature is exclusive to the LT3755-1 family (e.g., LT3755IUD-1#TRPBF). The LT3755IUD#TRPBF uses the RT pin for internal frequency programming only; Pin 9 is configured as OPENLED, not SYNC.
LT3755IUD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT3755IUD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755IUD#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 LT3755IUD#TRPBF reliable?
The price and inventory of LT3755IUD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3755IUD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3755IUD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755IUD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755IUD#TRPBF?
LT3755IUD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755IUD#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 LT3755IUD#TRPBF?
For technical support, including LT3755IUD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755IUD#TRPBF requirements.
6.How does Aetrix verify that LT3755IUD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3755IUD#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 LT3755IUD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3755IUD#TRPBF?
All LT3755IUD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755IUD#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 LT3755IUD#TRPBF part is unused and in its original packaging.
Return procedure for LT3755IUD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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