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Analog Devices Inc. LT3755EUD#TRPBF
- Part No.:
- LT3755EUD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755EUD#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:7,872
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Product details
Overview
LT3755EUD#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 integrated 7.15V INTVCC regulator - used in automotive LED headlamps and industrial high-power lighting.
For engineers reviewing the LT3755EUD#TRPBF datasheet, LT3755EUD#TRPBF pinout, LT3755EUD#TRPBF application, or LT3755EUD#TRPBF equivalent, key selection considerations include high-side current sense architecture, programmable 100kHz–1MHz switching frequency, AEC-Q100 qualification (E-grade), open LED protection via FB-based detection, and thermal shutdown with 125°C max junction temperature.
Technical Context
The LT3755EUD#TRPBF implements fixed-frequency current-mode control with slope compensation, using an internal transconductance error amplifier (VC) to regulate either LED current (via ISP/ISN differential sensing) or output voltage (via FB). Its dual-loop capability allows simultaneous or selective regulation - current loop dominates when CTRL > 1.2V and ISP–ISN > 2.9V; voltage loop activates when FB deviates from 1.25V nominal reference.
It integrates a 7.15V LDO for gate drive and logic, supports soft-start via SS pin with 10µA pull-up, and includes dedicated protection circuits: open LED detection (FB < VFB – 50mV), overvoltage shutdown (FB > VFB + 60mV), short-circuit detection (ISP–ISN > 150mV at ISN < 3V), and thermal limit at 165°C. The GATE driver delivers fast rise/fall times (<35ns) into 3300pF loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 40V - supports wide-range battery and industrial supply inputs without pre-regulation |
| Output Voltage Capability | Up to 75V - enables long LED strings in automotive headlamp and signage applications |
| 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 optimize efficiency, EMI, or magnetics size |
| Dimming Ratio | 3000:1 true-color PWM - preserves LED chromaticity across full brightness range |
| Operating Junction Temp | –40°C to +125°C - qualified for under-hood automotive environments per AEC-Q100 Grade E |
| Package | 16-lead 3mm × 3mm QFN with exposed pad - thermally enhanced for high-power LED driver PCB layouts |
Pinout & Package
LT3755EUD#TRPBF uses a thermally enhanced 16-lead (3mm × 3mm) plastic QFN package with exposed ground pad (Pin 17). Pin numbering follows standard top-view layout; exposed pad must be soldered 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 fault to isolate LED load |
| FB (Pin 2) | Voltage feedback input | Regulates output voltage to 1.25V; triggers OPENLED pull-down if below VFB – 50mV (open LED) |
| 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 input; combined with ISN to set LED current ILED = 100mV/RSENSE |
| VC (Pin 5) | Error amplifier output | Integrates difference between ISP–ISN and CTRL-set threshold; stabilizes loop with RC network |
| CTRL (Pin 6) | Current threshold adjust | Sets ISP–ISN regulation point: 100mV (full scale) when VCTRL > 1.2V; linear scaling below 1V |
| VREF (Pin 7) | 2.0V reference output | Supplies bias for CTRL divider; supports analog dimming and temperature compensation circuits |
| PWM (Pin 8) | Digital dimming input | Active-high signal enabling/disabling switching; internal pull-down; controls PWMOUT and oscillator |
| 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 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 → ~1MHz, 1MΩ → ~100kHz |
| SHDN/UVLO (Pin 12) | Shutdown & UVLO input | 1.22V falling threshold with programmable hysteresis; disables IC and resets soft-start on undervoltage |
| INTVCC (Pin 13) | Internal regulated supply | 7.15V LDO output powering GATE, PWMOUT, and internal logic; requires 4.7µF local ceramic bypass |
| VIN (Pin 14) | Main input supply | 4.5V–40V input; must be bypassed with ≥0.22µF ceramic capacitor near pin |
| SENSE (Pin 15) | Low-side current sense | Kelvin-connected to source of external sense resistor; monitors switch current for current-mode control |
| GATE (Pin 16) | MOSFET gate driver | Drives external N-channel FET between INTVCC and GND; fast 35ns rise/fall into 3300pF |
| Exposed Pad (Pin 17) | Thermal & electrical ground | 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 flexible topology selection (boost/buck/buck-boost/SEPIC/flyback) without ground-referenced LED cathode constraints |
| Programmable switching frequency | 100kHz–1MHz adjustment via single RT resistor - balances efficiency, EMI, and magnetic component size |
| True-color PWM dimming | 3000:1 ratio preserves LED color point across full intensity range - critical for automotive lighting compliance |
| AEC-Q100 Grade E qualification | Validated for automotive under-hood operation from –40°C to +125°C junction temperature |
| Integrated open LED and overvoltage protection | FB-based fault detection triggers OPENLED status and forces PWMOUT low - eliminates need for external monitoring circuitry |
| Thermally enhanced QFN package | 3mm × 3mm footprint with exposed pad achieves θJA = 68°C/W - sustains high-power LED driver operation without heatsink |
Applications
| Automotive LED Headlamps | Battery-Powered High-Brightness Lighting |
|---|---|
Use Scenario: 50W white LED headlamp module in passenger vehicle front lighting system, operating from 8V–16V battery with cold-crank down to 6V. IC Role / Device Role / Timing Role: Constant-current LED controller regulating string current via high-side ISP/ISN sensing; manages boost topology to maintain 75V output during low-input conditions. Use Value: AEC-Q100 qualification ensures reliability in under-hood thermal cycling; 3000:1 PWM dimming enables adaptive driving beam (ADB) functionality without color shift. | Use Scenario: Portable inspection lamp powered by 12V sealed lead-acid battery, requiring stable 3A LED current across discharge curve. IC Role / Device Role / Timing Role: Buck-mode LED controller using SENSE pin for low-side current sensing; adjusts duty cycle dynamically as VIN drops from 13.8V to 10.5V. Use Value: Wide 4.5V–40V input range accommodates full battery discharge profile; programmable UVLO prevents deep discharge damage. |
| Industrial Signage Backlighting | UV-C LED Disinfection Systems |
Use Scenario: Large-format outdoor LED sign with 24V DC input and multi-string parallel LED arrays requiring uniform brightness and thermal derating. IC Role / Device Role / Timing Role: Constant-voltage regulator via FB pin, with current limiting enforced by CTRL-adjusted ISP–ISN threshold to prevent overcurrent during ambient temperature rise. Use Value: Dual-loop architecture allows seamless transition between CV and CC modes; FB open-LED detection alerts controller to string failure before thermal runaway. | Use Scenario: Pulsed UV-C LED array (275nm) driven at 1A peak for surface disinfection, requiring precise current control and fast fault response. IC Role / Device Role / Timing Role: High-frequency (600kHz) current-mode controller in boost configuration; uses PWM input for microsecond-level pulse control and OPENLED for real-time string integrity monitoring. Use Value: 100mV current sense threshold minimizes power loss in shunt resistor; short-circuit detection (ISP–ISN > 150mV) protects expensive UV-C LEDs from catastrophic failure. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3756EUD#TRPBF | Higher 60V ISP/ISN common-mode range (vs 75V), identical pinout and feature set; supports up to 150V output in boost mode | Targeted at ultra-high-voltage LED strings (>100V) and laser diode drivers where extended ISP/ISN voltage tolerance is required | Select LT3756EUD#TRPBF only when output voltage exceeds 75V or ISP/ISN common-mode voltage exceeds 75V - otherwise LT3755EUD#TRPBF offers optimal cost/performance balance |
| LM3410XMF/NOPB | Single-stage buck-only controller; no high-side sensing, no OPENLED, lower 32V output capability, no AEC-Q100 rating | Suitable for low-cost, non-automotive, low-power (<15W) LED lighting with fixed input voltage and simple CV/CC requirements | Choose LM3410XMF/NOPB for cost-sensitive consumer lighting where AEC-Q100, high-side sensing, and 75V capability are unnecessary |
Compared with LT3756EUD#TRPBF, the LT3755EUD#TRPBF trades ultra-high-voltage capability for tighter thermal performance in compact QFN packages; versus LM3410XMF/NOPB, it adds automotive qualification, topology flexibility, and robust fault protection - making it essential for safety-critical or high-reliability LED systems.
Availability
LT3755EUD#TRPBF is available at Aetrix Electronics and suitable for automotive LED headlamps, industrial signage backlighting, and UV-C disinfection systems requiring stable component supply, AEC-Q100 compliance, and high-efficiency constant-current regulation.
Supply support for LT3755EUD#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 precision instrumentation, industrial automation, communications, and automotive markets.
The LT3755 product line was designed specifically for high-reliability, high-efficiency LED driver applications demanding wide input range, flexible topology support, and integrated protection - targeting automotive front lighting and industrial solid-state lighting systems.
FAQ
What topology configurations does the LT3755EUD#TRPBF support?
The LT3755EUD#TRPBF supports boost, buck, buck-boost, SEPIC, and flyback topologies through its high-side current sensing architecture and flexible feedback structure. Unlike traditional controllers constrained to ground-referenced LED cathodes, the LT3755EUD#TRPBF's ISP/ISN inputs enable direct high-side sensing - allowing the LED string to float relative to ground. This eliminates topology limitations imposed by low-side sensing and makes LT3755EUD#TRPBF suitable for applications such as automotive headlamps where the LED anode must connect to battery voltage.
How does the LT3755EUD#TRPBF implement open LED detection?
The LT3755EUD#TRPBF implements open LED detection using the FB pin voltage level: when FB falls below VFB – 50mV (typically 1.20V), the OPENLED pin asserts a pull-down signal. This occurs because an open LED string causes the output voltage to rise uncontrollably, pulling FB above its regulation point - but once the feedback loop loses control, FB collapses due to lack of current flow. The LT3755EUD#TRPBF monitors this collapse and signals fault condition via OPENLED, enabling system-level diagnostics without external comparators.
Can the LT3755EUD#TRPBF operate with input voltage below 6V?
Yes, the LT3755EUD#TRPBF can operate with input voltage as low as 4.5V, but SHDN/UVLO pin operation requires special attention below 6V: per datasheet Note 3, the SHDN/UVLO pin must not exceed VIN for proper undervoltage lockout function. To ensure reliable startup and shutdown behavior at low VIN, tie SHDN/UVLO directly to VIN or use a resistor divider referenced to VIN instead of ground. Also, connecting INTVCC to VIN (instead of regulating) is recommended when VIN ≤ 8V to avoid dropout issues.
What is the role of the CTRL pin in the LT3755EUD#TRPBF?
The CTRL pin in the LT3755EUD#TRPBF sets the ISP–ISN current sense threshold: for VCTRL > 1.2V, the threshold is fixed at 100mV; for 0V < VCTRL < 1V, it scales linearly as (VCTRL – 100mV)/(10 × RSENSE). This enables analog dimming, temperature compensation (by feeding VREF into CTRL via thermistor divider), or dynamic current derating. Leaving CTRL unconnected causes undefined regulation - it must be actively driven or tied to VREF/GND depending on desired mode.
Does the LT3755EUD#TRPBF require external components for thermal protection?
No, the LT3755EUD#TRPBF includes internal thermal protection that activates at 165°C junction temperature, forcing GATE and PWMOUT low until temperature recovers. However, sustained operation above 125°C degrades lifetime - so external thermal design remains critical. The 3mm × 3mm QFN package with exposed pad must be soldered to a minimum 1cm² copper pour for effective heat dissipation. No external thermal sensor or circuitry is needed for basic overtemperature shutdown, as the LT3755EUD#TRPBF handles this autonomously.
LT3755EUD#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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LT3755EUD#TRPBF FAQ
1.How can I place an order for LT3755EUD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755EUD#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 LT3755EUD#TRPBF reliable?
The price and inventory of LT3755EUD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3755EUD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3755EUD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755EUD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755EUD#TRPBF?
LT3755EUD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755EUD#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 LT3755EUD#TRPBF?
For technical support, including LT3755EUD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755EUD#TRPBF requirements.
6.How does Aetrix verify that LT3755EUD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3755EUD#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 LT3755EUD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3755EUD#TRPBF?
All LT3755EUD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755EUD#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 LT3755EUD#TRPBF part is unused and in its original packaging.
Return procedure for LT3755EUD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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