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Analog Devices Inc. LT3755EUD-2#TRPBF
- Part No.:
- LT3755EUD-2#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LT3755EUD-2#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,455
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Product details
Overview
LT3755EUD-2#TRPBF from Analog Devices is a constant-current, current-mode DC/DC LED controller driving external N-channel MOSFETs in boost, buck, buck-boost, SEPIC, or flyback topologies. It features 4.5V–40V input range, 75V output capability, 100kHz–1MHz adjustable switching frequency, high-side current sensing with 100mV threshold, and AEC-Q100 qualification for automotive headlamp drivers.
For engineers reviewing the LT3755EUD-2#TRPBF datasheet, LT3755EUD-2#TRPBF pinout, LT3755EUD-2#TRPBF application, or LT3755EUD-2#TRPBF equivalent, key selection criteria include open LED protection behavior (LT3755-2 variant), CTRL-based analog dimming, PWM dimming up to 3000:1, thermal shutdown at 165°C, and QFN-16 (3mm × 3mm) package with exposed pad grounding.
Technical Context
The LT3755EUD-2#TRPBF implements fixed-frequency current-mode control with internal 7.15V INTVCC regulator powering gate driver and logic. Its high-side current sense architecture (ISP/ISN inputs) enables topology flexibility and avoids ground loop issues in LED string configurations.
It integrates dual-loop regulation: LED current control via ISP–ISN differential voltage referenced to CTRL pin (100mV full-scale), and optional constant-voltage regulation via FB pin (1.25V reference). The LT3755-2 variant adds improved OPENLED status latching behavior during PWM idle states and replaces SYNC functionality with OPENLED on Pin 9.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 40V - supports 12V/24V automotive battery rails with cold-crank margin |
| Output Voltage Capability | Up to 75V - enables driving long LED strings (e.g., 20× white LEDs @ 3.5V) |
| Switching Frequency Range | 100kHz to 1MHz - set by RT resistor; higher frequencies reduce inductor size but increase switching loss |
| Current Sense Threshold | 100mV (typical) at ISP–ISN - sets LED current as ILED = 100mV / Rsense when CTRL > 1.2V |
| CTRL Pin Adjustment Range | 0V to 1.1V - linearly scales current threshold from 0mV to 100mV for analog dimming |
| Open LED Detection | FB < 1.20V (typical) - asserts OPENLED pull-down to signal LED string disconnection |
| Shutdown Current | <1µA - achieved by pulling SHDN/UVLO ≤ 0.4V; critical for always-on automotive systems |
Pinout & Package
LT3755EUD-2#TRPBF uses a thermally enhanced 16-lead (3mm × 3mm) plastic QFN package with exposed pad (Pin 17) soldered to PCB ground for thermal and electrical integrity. Pin numbering follows standard QFN top-view layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PWMOUT (Pin 1) | Buffered PWM output | Drives NMOS disconnect switch; toggles low if FB exceeds 1.31V to protect LEDs from overvoltage |
| FB (Pin 2) | Voltage feedback input | Regulates to 1.25V; enables CV mode and open-LED detection (FB < 1.20V asserts OPENLED) |
| ISN (Pin 3) | Negative current sense input | Kelvin-connected to low side of sense resistor; bias current ~25µA; short-circuit detection active below 3V |
| ISP (Pin 4) | Positive current sense input | Kelvin-connected to high side of sense resistor; bias current varies with CTRL voltage |
| VC (Pin 5) | Error amplifier output | High-impedance during PWM low; stores demand state; requires RC compensation network to GND |
| CTRL (Pin 6) | Current threshold adjust | Sets ISP–ISN threshold from 0–100mV; 0–1.1V range provides linear analog dimming control |
| VREF (Pin 7) | 2.0V reference output | Stable 2.0V source (±2%); supplies current to CTRL divider or temperature compensation circuitry |
| PWM (Pin 8) | Digital dimming input | Active-high; enables/disables switching; internal pull-down; supports 3000:1 PWM dimming ratio |
| OPENLED (Pin 9) | Open-circuit fault indicator | Open-collector output; pulled low when FB < 1.20V; latched during PWM idle (LT3755-2 specific) |
| SS (Pin 10) | Soft-start timing | 10µA internal 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; 10kΩ → ~1MHz |
| SHDN/UVLO (Pin 12) | Enable & undervoltage detect | 1.22V falling threshold; hysteresis programmable via external divider; disables IC below threshold |
| INTVCC (Pin 13) | Internal LDO output | 7.15V regulated supply; powers gate driver and logic; requires 4.7µF local ceramic bypass |
| VIN (Pin 14) | Main power input | Accepts 4.5–40V; must be bypassed with ≥0.22µF ceramic capacitor near pin |
| SENSE (Pin 15) | Low-side switch current sense | Kelvin-connected to source of external NMOS; monitors switch current for slope compensation |
| GATE (Pin 16) | MOSFET gate driver | Drives external N-channel FET between INTVCC and GND; rise/fall time <35ns (CL=3300pF) |
| Exposed Pad (Pin 17) | Thermal & electrical ground | Must be soldered to PCB ground plane; improves thermal resistance (θJC = 4.2°C/W) and noise immunity |
Key Features
| Feature | Design Value |
|---|---|
| High-side current sensing | Enables topology agnosticism (boost/buck/buck-boost/SEPIC/flyback) without compromising ground-referenced LED cathode |
| 3000:1 true-color PWM dimming | Preserves LED chromaticity across full dimming range; eliminates color shift in automotive lighting |
| Improved OPENLED latching (LT3755-2) | Latches fault state during PWM idle and updates only on next PWM high transition - ensures reliable fault reporting in pulsed operation |
| AEC-Q100 qualified (Grade E) | Validated for –40°C to +125°C junction operation; meets automotive reliability and stress testing requirements |
| Programmable soft-start | External capacitor on SS pin controls startup dI/dt and prevents inrush into large output capacitors or LED strings |
Applications
| Automotive LED Headlamps | Battery-Powered LED Lighting |
|---|---|
Use Scenario: High-brightness adaptive front-lighting system (AFS) in passenger vehicles requiring precise current regulation and fault diagnostics. IC Role / Device Role / Timing Role: Constant-current LED controller managing 50W+ white LED arrays; provides open-LED detection and overvoltage protection via FB and OPENLED pins. Use Value: Enables AEC-Q100-compliant headlamp designs with 3000:1 dimming, thermal derating, and fail-safe status signaling under ISO 16750-2 load dump conditions. | Use Scenario: Portable medical device illumination or ruggedized industrial flashlight with variable brightness and battery life optimization. IC Role / Device Role / Timing Role: Primary LED driver operating from Li-ion (3.0–4.2V) or 12V sealed lead-acid battery; uses buck topology for efficiency. Use Value: Delivers stable LED current across wide input range (4.5–40V), extends runtime via <1µA shutdown current, and supports analog + PWM dimming for user interface flexibility. |
| Industrial LED Signage | UV-C LED Disinfection Systems |
Use Scenario: Outdoor digital signage requiring high-lumen output, thermal management, and long-term reliability in varying ambient temperatures. IC Role / Device Role / Timing Role: Constant-current controller in boost configuration driving multi-string parallel LED arrays; regulates via ISP/ISN with CTRL dimming. Use Value: Maintains consistent luminance despite input voltage sag or temperature drift; high-side sensing avoids ground contamination in multi-board installations. | Use Scenario: Pulsed UV-C LED arrays used in surface disinfection equipment where precise current control prevents LED degradation. IC Role / Device Role / Timing Role: Fast-response current controller enabling microsecond-level PWM bursts; leverages high-side sensing for accurate per-string current matching. Use Value: Ensures repeatable UV dose delivery by maintaining ±1% LED current accuracy across pulse widths down to 100µs, critical for germicidal efficacy. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3756EUD-2#TRPBF | Higher 60V ISP/ISN common-mode range (vs 75V), same pinout and CTRL/PWM dimming; adds spread-spectrum frequency modulation | Better EMI performance in sensitive RF environments; identical automotive qualification and thermal specs | Select when board-level EMI compliance (CISPR 25 Class 5) is required without layout changes |
| LM3410XSDX/NOPB | Single-stage buck-only controller; 4.5–24V input; no high-side sensing; fixed 1.6MHz frequency; no OPENLED or CTRL analog dimming | Limited to low-output-voltage LED strings; lacks fault reporting and flexible dimming; lower BOM cost | Select for cost-sensitive, non-automotive, single-string buck applications where topology and diagnostics are constrained |
Compared with LT3755EUD-2#TRPBF, LT3756EUD-2#TRPBF offers superior EMI control for automotive EMC compliance, while LM3410XSDX/NOPB trades topology flexibility and diagnostics for lower cost and simpler implementation in fixed-buck systems.
Availability
LT3755EUD-2#TRPBF is available at Aetrix Electronics and suitable for automotive headlamp drivers, battery-powered portable lighting, industrial signage, and UV-C disinfection systems requiring stable component supply, AEC-Q100 qualification, and high-reliability current regulation.
Supply support for LT3755EUD-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.
The LT3755 product line delivers high-voltage, high-current LED controllers optimized for automotive-grade reliability, flexible topology support, and precision current regulation in demanding lighting applications.
FAQ
What is the key functional difference between LT3755EUD-2#TRPBF and the base LT3755EUD#TRPBF?
The LT3755EUD-2#TRPBF implements an improved OPENLED latching mechanism: during PWM idle periods, it retains the last valid open-LED fault state and updates only upon the next PWM high transition. This ensures robust fault reporting in pulsed-dimming automotive applications, unlike the base LT3755 which de-asserts OPENLED during idle. All other electrical specs and pinout remain identical for LT3755EUD-2#TRPBF.
Can LT3755EUD-2#TRPBF operate in buck topology with a grounded LED cathode?
Yes, LT3755EUD-2#TRPBF supports buck topology with grounded LED cathode using high-side current sensing. Connect the LED anode to VOUT, cathode to ground, and place the current sense resistor between ISP and ISN in series with the LED string's high side. This preserves ground reference for MCU interfaces and avoids noise coupling into low-side sensing paths - a key advantage confirmed in the LT3755EUD-2#TRPBF datasheet Figure 1.
What is the minimum recommended value for the RT resistor to achieve 1MHz switching on LT3755EUD-2#TRPBF?
The LT3755EUD-2#TRPBF achieves approximately 1MHz switching frequency with a 10kΩ resistor from RT to GND, as verified in the "Switching Frequency vs RT" typical performance curve (Figure 7). Using a precision 1% metal-film resistor ensures stable operation. Values below 10kΩ risk exceeding maximum oscillator frequency limits and may cause instability or increased jitter - the datasheet specifies 10kΩ as the practical lower bound for reliable 1MHz operation on LT3755EUD-2#TRPBF.
How does the CTRL pin affect LED current regulation in LT3755EUD-2#TRPBF?
The CTRL pin on LT3755EUD-2#TRPBF directly scales the ISP–ISN current sense threshold: for 0V < VCTRL < 1V, threshold = (VCTRL – 0.1V) × 10; above 1.2V, threshold is fixed at 100mV. This enables precise analog dimming - e.g., 0.5V on CTRL yields 40mV threshold, reducing LED current to 40% of full scale. The relationship is monotonic and specified across temperature, making LT3755EUD-2#TRPBF suitable for closed-loop thermal compensation circuits.
Is LT3755EUD-2#TRPBF compatible with 5V logic-level PWM signals?
Yes, LT3755EUD-2#TRPBF accepts 5V PWM signals directly: its PWM input high threshold is 1.5V (min), and absolute maximum rating is 12V. With internal pull-down, a 5V CMOS signal cleanly meets logic high requirements while staying within safe operating limits. No level-shifting is needed, simplifying interface design with microcontrollers or FPGA outputs - a confirmed capability in the "Logic Inputs/Outputs" section of the LT3755EUD-2#TRPBF datasheet.
LT3755EUD-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:
- 0°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LT3755EUD-2#TRPBF FAQ
1.How can I place an order for LT3755EUD-2#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755EUD-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 LT3755EUD-2#TRPBF reliable?
The price and inventory of LT3755EUD-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 LT3755EUD-2#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3755EUD-2#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755EUD-2#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755EUD-2#TRPBF?
LT3755EUD-2#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755EUD-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 LT3755EUD-2#TRPBF?
For technical support, including LT3755EUD-2#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755EUD-2#TRPBF requirements.
6.How does Aetrix verify that LT3755EUD-2#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3755EUD-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 LT3755EUD-2#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3755EUD-2#TRPBF?
All LT3755EUD-2#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755EUD-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 LT3755EUD-2#TRPBF part is unused and in its original packaging.
Return procedure for LT3755EUD-2#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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