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Analog Devices Inc. LT3755IMSE-2#PBF
- Part No.:
- LT3755IMSE-2#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3755IMSE-2#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,039
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Product details
Overview
LT3755IMSE-2#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, 3000:1 PWM dimming, and AEC-Q100 qualification for automotive headlamp drivers.
For engineers reviewing the LT3755IMSE-2#PBF datasheet, LT3755IMSE-2#PBF pinout, LT3755IMSE-2#PBF application, or LT3755IMSE-2#PBF equivalent, key selection considerations include its open-LED protection with improved status signaling (LT3755-2 variant), programmable 100kHz–1MHz switching frequency, and dual-loop constant-current/constant-voltage regulation for high-power LED systems.
Technical Context
The LT3755IMSE-2#PBF implements fixed-frequency current-mode control with internal 7.15V INTVCC regulator powering gate and PWMOUT drivers. Its high-side ISP/ISN current sensing enables topology flexibility, while the VC error amplifier integrates feedback from both LED current (via CTRL-adjusted 100mV threshold) and output voltage (via FB pin referenced to 1.25V).
Unlike LT3755-1 (SYNC-capable) and base LT3755, the -2 variant replaces SYNC functionality with enhanced OPENLED status latching-asserting pull-down when FB drops 50mV below regulation and re-asserting after overvoltage recovery-enabling robust fault reporting in automotive lighting without external logic.
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 - drives multi-series white LED strings in headlamp applications |
| Current Sense Threshold | 100mV (typical) at ISP–ISN - enables precise, low-loss high-side sensing with 0.1Ω shunt |
| Switching Frequency Range | 100kHz to 1MHz - adjustable via RT resistor for EMI optimization or magnetics size reduction |
| Dimming Ratio | 3000:1 true-color PWM - maintains chromaticity across full brightness range in display and lighting |
| Operating Junction Temp | –40°C to 125°C - qualified per AEC-Q100 Grade I for under-hood automotive use |
| Shutdown Current | <1µA - enables always-on vehicle systems with minimal battery drain |
Pinout & Package
LT3755IMSE-2#PBF uses a thermally enhanced 16-lead plastic MSOP package (3mm × 4.9mm) with exposed pad soldered to PCB ground for thermal dissipation and current sense return path.
| 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 to 1.25V reference; triggers OPENLED pull-down when < VFB – 50mV (open-LED detection) |
| ISN (Pin 3) | Negative current sense input | High-side shunt return; enables short-circuit detection when ISN < 3V and ISP–ISN > 150mV |
| ISP (Pin 4) | Positive current sense input | High-side shunt connection point; bias current varies with CTRL voltage for analog dimming |
| VC (Pin 5) | Error amplifier output | Integrates current/voltage loop errors; high-impedance during PWM low to retain state |
| CTRL (Pin 6) | Current threshold adjust | Sets ISP–ISN threshold from 0V to 100mV linearly (0–1V) then clamps at full scale (>1.2V) |
| VREF (Pin 7) | 2.0V reference output | Stable 2.0V source for CTRL divider or temperature compensation networks; supplies ≤100µA |
| PWM (Pin 8) | Digital dimming input | Active-low shutdown; resets soft-start and forces GATE/PWMOUT low when asserted |
| OPENLED (Pin 9) | Open-LED status output | Open-collector pull-down (LT3755-2 only); latched status updates on PWM rising edge |
| SS (Pin 10) | Soft-start control | 10µA 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 = ~1MHz, 1MΩ = ~100kHz |
| SHDN/UVLO (Pin 12) | Enable & undervoltage lockout | 1.22V falling threshold with programmable hysteresis; sub-µA bias above threshold |
| INTVCC (Pin 13) | Internal LDO output | 7.15V regulated supply for gate driver; 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 shunt positive; monitors switch current for slope-compensated current mode |
| GATE (Pin 16) | MOSFET driver output | Switches between INTVCC and GND; drives external N-channel FET gate directly |
| Exposed Pad | Thermal & electrical ground | Must be soldered to PCB ground plane; serves as current sense return and thermal path |
Key Features
| Feature | Design Value |
|---|---|
| High-side current sensing | Enables flexible topology selection (boost/buck/buck-boost/SEPIC/flyback) without ground-referenced LED strings |
| Improved OPENLED status (LT3755-2) | Latched fault reporting that re-asserts after overvoltage recovery-critical for automotive diagnostics compliance |
| Programmable 100kHz–1MHz frequency | Optimizes efficiency vs. EMI trade-off and allows smaller inductors/capacitors in space-constrained designs |
| Dual-loop regulation | Simultaneous constant-current (LED string) and constant-voltage (output bus) control prevents overvoltage damage during open-circuit faults |
| AEC-Q100 Grade I qualification | Validated for automotive under-hood operation from –40°C to +125°C junction temperature |
Applications
| Automotive LED Headlamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: 50W white LED headlamp driver in passenger vehicle front lighting system. IC Role / Device Role / Timing Role: Constant-current controller regulating 1.5A through 12-series white LEDs with adaptive dimming and fault reporting. Use Value: AEC-Q100 qualification ensures reliability under thermal cycling and vibration; OPENLED latching meets OEM diagnostic requirements. | Use Scenario: Multi-string LED fixture for warehouse ceiling lighting with 0–10V analog dimming interface. IC Role / Device Role / Timing Role: Buck-mode LED driver delivering 350mA per string with CTRL-based analog dimming and FB-based overvoltage clamp. Use Value: Dual-loop regulation prevents LED overvoltage during partial-string failure; 3000:1 PWM dimming enables smooth architectural lighting transitions. |
| Battery-Powered Portable Lighting | UV-C LED Disinfection Systems |
Use Scenario: Rechargeable handheld spotlight using 3S Li-ion battery (9–12.6V) driving 3-series blue LEDs. IC Role / Device Role / Timing Role: Boost converter maintaining 350mA constant current across battery discharge curve. Use Value: Wide 4.5V–40V input range accommodates full Li-ion voltage swing; <1µA shutdown current extends standby runtime. | Use Scenario: Pulsed UV-C LED array (275nm) for surface disinfection requiring precise current control and thermal derating. IC Role / Device Role / Timing Role: Constant-current driver with CTRL-based thermal foldback and ISP/ISN short-circuit protection. Use Value: High-side sensing avoids ground loop interference in isolated UV driver stages; 100mV sense threshold minimizes power loss in high-current arrays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3756IMSE-2#PBF | Higher 60V ISP/ISN common-mode rating (vs. 75V), identical pinout and feature set, but rated for 150°C max junction temp (H/J grade only) | Targeted at higher ambient temperature environments (e.g., enclosed outdoor fixtures) where 125°C limit is insufficient | Select LT3756IMSE-2#PBF only if operating junction temperature exceeds 125°C; otherwise LT3755IMSE-2#PBF offers same functionality at lower cost |
| LM3423MH/NOPB | Non-synchronous buck-only controller; lacks boost/buck-boost/SEPIC capability; no OPENLED latching; 1.23V FB reference vs. 1.25V | Cost-sensitive, single-topology industrial lighting where topology flexibility and automotive diagnostics are unnecessary | Choose LM3423MH/NOPB for simplified buck-only designs with lower BOM count; avoid when high-side sensing or AEC-Q100 compliance is required |
Compared with LT3756IMSE-2#PBF, LT3755IMSE-2#PBF provides identical functionality at lower thermal rating-sufficient for most automotive cabin and headlamp applications-while LM3423MH/NOPB sacrifices topology flexibility and diagnostic features for cost reduction in non-automotive buck-only systems.
Availability
LT3755IMSE-2#PBF is available at Aetrix Electronics and suitable for automotive LED headlamps, industrial high-bay lighting, and battery-powered portable lighting requiring stable component supply, AEC-Q100 compliance, and high-reliability current regulation.
Supply support for LT3755IMSE-2#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3755 family was designed specifically for high-power LED lighting systems requiring robust fault protection, flexible topology support, and automotive-grade reliability-targeting headlamp, fog lamp, and commercial lighting applications.
FAQ
What distinguishes LT3755IMSE-2#PBF from LT3755IMSE#PBF and LT3755IMSE-1#PBF?
The LT3755IMSE-2#PBF replaces the SYNC pin of LT3755IMSE-1#PBF with an enhanced OPENLED function that latches open-LED status and re-asserts it after overvoltage recovery-critical for automotive diagnostics. Unlike the base LT3755IMSE#PBF, the -2 variant includes this improved fault reporting without SYNC capability. All share identical pinout, package, and core regulation architecture.
How does the LT3755IMSE-2#PBF implement dual-loop constant-current and constant-voltage regulation?
The LT3755IMSE-2#PBF uses two independent feedback paths: ISP/ISN senses LED current and compares it to a CTRL-adjustable threshold (up to 100mV), while FB monitors output voltage against a 1.25V internal reference. The VC error amplifier integrates both signals, prioritizing current regulation under normal operation but clamping output voltage if FB exceeds its threshold-preventing overvoltage damage during open-circuit faults.
Can LT3755IMSE-2#PBF drive LEDs in buck configuration with high-side current sensing?
Yes. The LT3755IMSE-2#PBF supports buck topology using high-side current sensing via ISP/ISN pins, enabling the LED string to remain grounded-a key safety and EMI advantage. In buck mode, the external N-channel MOSFET switches the high-side rail, while ISP/ISN measures current through a shunt placed between the LED cathode and ground, preserving ground-referenced LED placement.
What is the purpose of the exposed pad on the LT3755IMSE-2#PBF MSOP package?
The exposed pad on the LT3755IMSE-2#PBF serves two critical functions: it provides a low-thermal-resistance path to the PCB ground plane (θJC = 4°C/W) for dissipating up to 1.5W of power, and it acts as the current sense return path for the high-side shunt-requiring direct soldering to the PCB ground plane to maintain measurement accuracy and thermal stability.
How does the LT3755IMSE-2#PBF handle open-LED fault detection and reporting?
The LT3755IMSE-2#PBF detects open-LED conditions when FB falls below VFB – 50mV (1.20V typical), asserting the OPENLED pin as an open-collector pull-down. Unlike earlier variants, the LT3755-2 latches this state and re-asserts it after FB recovers from overvoltage events-ensuring continuous fault reporting during transient overvoltages common in automotive load-dump scenarios.
LT3755IMSE-2#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width) 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-MSOP-EP
LT3755IMSE-2#PBF FAQ
1.How can I place an order for LT3755IMSE-2#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3755IMSE-2#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 LT3755IMSE-2#PBF reliable?
The price and inventory of LT3755IMSE-2#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3755IMSE-2#PBF is usually 5 days.
3.What payment methods are accepted for LT3755IMSE-2#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3755IMSE-2#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3755IMSE-2#PBF?
LT3755IMSE-2#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3755IMSE-2#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 LT3755IMSE-2#PBF?
For technical support, including LT3755IMSE-2#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3755IMSE-2#PBF requirements.
6.How does Aetrix verify that LT3755IMSE-2#PBF is sourced from the original manufacturer or authorized distributors?
All LT3755IMSE-2#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 LT3755IMSE-2#PBF meets industry standards.
7.What is the process for return or replacement of LT3755IMSE-2#PBF?
All LT3755IMSE-2#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3755IMSE-2#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 LT3755IMSE-2#PBF part is unused and in its original packaging.
Return procedure for LT3755IMSE-2#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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