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Analog Devices Inc. LT3755IUD-2#TRPBF
- Part No.:
- LT3755IUD-2#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755IUD-2#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,220
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Product details
Overview
LT3755IUD-2#TRPBF from Analog Devices is a high-voltage, constant-current LED controller IC designed for automotive and industrial LED drivers. It operates as a current-mode DC/DC controller driving external N-channel MOSFETs, supports 4.5V–40V input, delivers up to 75V output, enables 3000:1 PWM dimming, and features high-side current sensing for boost/buck/buck-boost topologies.
For engineers reviewing the LT3755IUD-2#TRPBF datasheet, LT3755IUD-2#TRPBF pinout, LT3755IUD-2#TRPBF application, or LT3755IUD-2#TRPBF equivalent, key selection criteria include its AEC-Q100 qualification, 100kHz–1MHz adjustable switching frequency, open LED protection with dedicated OPENLED pin, 100mV high-side current sense threshold, and thermally enhanced 3mm × 3mm QFN package with exposed ground pad.
Technical Context
The LT3755IUD-2#TRPBF implements fixed-frequency current-mode control with internal 7.15V INTVCC regulator, ground-referenced FB pin enabling dual constant-current/constant-voltage regulation, and programmable soft-start via SS pin. Its high-side ISP/ISN current sensing architecture decouples LED string grounding from power stage layout constraints.
Unlike LT3755-1 (SYNC-capable) and base LT3755, the -2 variant integrates an improved OPENLED status pin with re-assertion logic after overvoltage recovery and excludes SYNC functionality-making it optimized for fault-reporting-critical LED headlamp and signage applications where open-load detection reliability is prioritized over clock synchronization.
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 transients. |
| Output Voltage Capability | Up to 75V - enables driving long LED strings in single-stage boost configurations. |
| Switching Frequency Range | 100kHz to 1MHz - adjustable via RT resistor to balance efficiency, EMI, and magnetics size. |
| Current Sense Threshold | 100mV (typical) at ISP–ISN - enables precise, low-loss high-side current sensing with minimal voltage drop. |
| Dimming Ratio | 3000:1 true-color PWM dimming - 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 I. |
| Package | 16-lead 3mm × 3mm QFN with exposed thermal pad - provides low θJA = 68°C/W for high-power density layouts. |
Pinout & Package
LT3755IUD-2#TRPBF is housed in a thermally enhanced 16-lead plastic QFN (3mm × 3mm) with exposed ground pad (Pin 17), rated for –40°C to +125°C operation. The exposed pad must be soldered to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PIN 1 (VREF) | Voltage reference output | 2.00V ±1.5% source for CTRL biasing or temperature compensation networks; supplies ≤100µA. |
| PIN 2 (PWM) | Digital dimming enable input | Active-low shutdown with internal pull-down; controls PWMOUT and oscillator wake-up timing. |
| PIN 3 (OPENLED) | Open-load fault indicator | Open-collector output asserting when FB < VFB −50mV; latched during PWM low, re-asserted post-overvoltage recovery (LT3755-2 specific). |
| PIN 4 (SS) | Soft-start control | 10µA pull-up to 2.5V rail; external capacitor sets ramp time; reset by UVLO or thermal fault. |
| PIN 5 (FB) | Voltage feedback input | Regulates to 1.25V nominal; enables CV mode and open-LED detection; must not float. |
| PIN 6 (PWMOUT) | Buffered PWM output | INTVCC-referenced gate driver for NMOS disconnect switch; toggles low if FB > VFB +60mV for overvoltage protection. |
| PIN 7 (GATE) | NMOS gate driver output | Drives external low-side N-channel FET between INTVCC and GND; fast 35ns rise/fall times. |
| PIN 8 (SENSE) | Low-side current sense input | Kelvin-connected to RSENSE positive terminal; limits peak switch current at 108mV threshold. |
| PIN 9 (CTRL) | Analog dimming / current setpoint | Adjusts ISP–ISN threshold from 0V to 100mV linearly (0–1V) then clamps; enables analog dimming or thermal derating. |
| PIN 10 (VC) | Error amplifier output | High-impedance transconductance node; RC network stabilizes voltage loop; stores state during PWM low. |
| PIN 11 (ISP) | High-side current sense (+) | Accepts up to 75V common-mode; bias current varies with CTRL voltage; part of short-circuit detection below 3V. |
| PIN 12 (ISN) | High-side current sense (−) | Ground-referenced return for ISP; enables high-side sensing without floating grounds; short-circuit threshold = 150mV above ISN. |
| PIN 13 (RT) | Frequency programming | Resistor-to-GND sets oscillator frequency; 100kΩ → ~375kHz; supports 100kHz–1MHz range. |
| PIN 14 (SHDN/UVLO) | Shutdown & input monitoring | 1.22V falling threshold with programmable hysteresis; sub-µA shutdown current; resets soft-start on undervoltage. |
| PIN 15 (INTVCC) | Internal LDO output | 7.15V regulated supply for gate/PWMOUT drivers; requires 4.7µF local ceramic bypass; current-limited to 34mA. |
| PIN 16 (VIN) | Main power input | Bypass with ≥0.22µF ceramic near pin; powers internal circuitry and charges INTVCC LDO. |
| PIN 17 (GND) | Power & signal ground | Exposed thermal pad; serves as Kelvin return for SENSE and ISN; must be soldered to PCB ground plane. |
Key Features
| Feature | Design Value |
|---|---|
| High-side current sensing | Enables flexible topology selection (boost/buck/buck-boost/SEPIC/flyback) without compromising LED string grounding or layout symmetry. |
| Improved OPENLED logic (LT3755-2) | Re-asserts open-load flag after FB recovers from overvoltage condition-critical for reliable fault reporting in safety-critical lighting. |
| AEC-Q100 Grade I qualification | Validated for automotive use across –40°C to +125°C junction temperature, supporting under-hood LED headlamp and DRL applications. |
| 100mV ISP–ISN sense threshold | Minimizes power loss in current-sense resistor while maintaining noise immunity and accuracy over temperature. |
| Programmable soft-start | Prevents inrush current and output overshoot via external capacitor on SS pin; automatically resets on UVLO or thermal fault. |
| Integrated 7.15V INTVCC LDO | Eliminates need for external bias supply; includes current limit (34mA typ) and UVLO (4.1V) to protect external FETs during brownout. |
Applications
| Automotive LED Headlamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: 50W white LED headlamp module operating from 8V–16V vehicle battery with load-dump tolerance. IC Role / Device Role / Timing Role: Constant-current controller regulating LED string current via high-side sensing; manages PWM dimming and open-LED fault signaling. Use Value: AEC-Q100 qualification ensures reliability in harsh under-hood environments; 3000:1 dimming preserves color fidelity for adaptive driving beam systems. |
Use Scenario: 100W high-bay fixture using multi-string parallel LEDs powered from 24VDC industrial bus. IC Role / Device Role / Timing Role: Primary current-mode controller in buck-boost topology delivering stable current despite wide input variation and thermal drift. Use Value: High-side sensing simplifies PCB layout for distributed LED arrays; programmable frequency avoids audible noise in factory settings. |
| Architectural LED Signage | UV-C LED Disinfection Systems |
Use Scenario: RGB pixelated signage requiring precise current matching across red/green/blue channels with analog + PWM dimming. IC Role / Device Role / Timing Role: Constant-current driver per channel with independent CTRL and PWM inputs enabling per-color intensity and hue control. Use Value: Dual dimming capability (3000:1 PWM + analog) enables smooth grayscale transitions and accurate white-point tuning. |
Use Scenario: Pulsed UV-C LED array (275nm) driven at high peak current for surface disinfection, requiring precise current limiting and fault isolation. IC Role / Device Role / Timing Role: High-voltage current controller with fast open-LED detection to prevent catastrophic failure of expensive UV LEDs during thermal stress. Use Value: OPENLED pin with re-assertion logic ensures continuous fault visibility even after transient overvoltage events common in pulsed operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EMSE#PBF | 4-switch synchronous buck-boost controller; no integrated gate driver; requires external MOSFETs and gate drivers. | Supports bidirectional power flow and higher efficiency at mid-input ranges; lacks dedicated OPENLED pin and AEC-Q100 rating. | Select when system requires >95% efficiency across 5V–36V input and bidirectional capability outweighs fault-reporting simplicity. |
| LM3414HVSDX/NOPB | Monolithic 40V buck LED driver with integrated 0.5Ω MOSFET; fixed 500kHz frequency; no high-side sensing or topology flexibility. | Lower BOM count and cost for simple low-power (<15W) boostless designs; no AEC-Q100 or open-LED status reporting. | Select for cost-sensitive, space-constrained consumer lighting where input stays within 6.5V–40V and output ≤40V. |
Compared with LTC3789EMSE#PBF and LM3414HVSDX/NOPB, the LT3755IUD-2#TRPBF uniquely combines AEC-Q100 qualification, high-side current sensing for topology freedom, and robust open-LED fault signaling in a compact QFN-making it optimal for automotive and industrial LED systems demanding reliability, flexibility, and diagnostics.
Availability
LT3755IUD-2#TRPBF is available at Aetrix Electronics and suitable for automotive LED headlamps, industrial high-bay lighting, architectural signage, and UV-C disinfection systems requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.
Supply support for LT3755IUD-2#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 with precision power, signal chain, and RF solutions.
The LT3755 product line was engineered specifically for high-reliability, high-power LED lighting applications-emphasizing wide input range, flexible topology support, robust fault protection, and automotive-grade qualification.
FAQ
What is the key functional difference between LT3755IUD-2#TRPBF and LT3755IUD#TRPBF?
The LT3755IUD-2#TRPBF integrates an improved OPENLED status pin that re-asserts the open-load fault signal after the FB pin recovers from an overvoltage event (FB > VFB +60mV), whereas the base LT3755IUD#TRPBF does not re-assert OPENLED until FB falls below both the open-LED and overvoltage thresholds. This makes LT3755IUD-2#TRPBF more reliable for continuous fault monitoring in safety-critical LED systems like automotive headlamps.
Does LT3755IUD-2#TRPBF support synchronization to an external clock?
No, LT3755IUD-2#TRPBF does not support external clock synchronization. The SYNC pin function is exclusive to the LT3755-1 variant (e.g., LT3755IUD-1#TRPBF). On LT3755IUD-2#TRPBF, Pin 3 is designated OPENLED-not SYNC-and the internal oscillator is only adjustable via the RT resistor. Attempting to drive a clock signal into Pin 3 will disrupt open-LED fault reporting.
What is the maximum recommended output voltage for LT3755IUD-2#TRPBF in boost configuration?
The absolute maximum ISP pin voltage is 75V, and the datasheet specifies "Output Voltage Up to 75V" for the LT3755 family. In boost configuration, LT3755IUD-2#TRPBF reliably regulates LED strings up to 75V-provided external components (MOSFET, diode, inductor, output capacitor) are rated accordingly and layout minimizes parasitic ringing. Exceeding 75V risks damage to the ISP/ISN input stage.
Can LT3755IUD-2#TRPBF operate in constant-voltage mode only, without LED current regulation?
Yes, LT3755IUD-2#TRPBF can operate exclusively in constant-voltage mode. Tie ISP and ISN together and connect CTRL to VREF (Pin 1) to disable the current loop; regulate output voltage via the FB pin referenced to its 1.25V internal threshold. The FB pin remains active for overvoltage protection and OPENLED reporting even in CV-only operation.
What thermal design considerations apply to the exposed pad of LT3755IUD-2#TRPBF?
The exposed pad (Pin 17) of LT3755IUD-2#TRPBF is electrically GND and thermally critical-θJA is specified at 68°C/W only when the pad is fully soldered to a minimum 100mm² copper area on the PCB. Use ≥4 thermal vias (0.3mm diameter) connecting the pad to inner/ground planes. Insufficient pad soldering or undersized copper will cause junction temperature to exceed 125°C, triggering thermal shutdown and reducing reliability.
LT3755IUD-2#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-2#TRPBF FAQ
1.How can I place an order for LT3755IUD-2#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755IUD-2#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-2#TRPBF reliable?
The price and inventory of LT3755IUD-2#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-2#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3755IUD-2#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755IUD-2#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755IUD-2#TRPBF?
LT3755IUD-2#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755IUD-2#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-2#TRPBF?
For technical support, including LT3755IUD-2#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755IUD-2#TRPBF requirements.
6.How does Aetrix verify that LT3755IUD-2#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3755IUD-2#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-2#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3755IUD-2#TRPBF?
All LT3755IUD-2#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755IUD-2#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-2#TRPBF part is unused and in its original packaging.
Return procedure for LT3755IUD-2#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3755IUD-2#TRPBF Tags
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