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Analog Devices Inc. LT3955IUHE#PBF
- Part No.:
- LT3955IUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3955IUHE#PBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3.5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,374
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Product details
Overview
LT3955IUHE#PBF from Analog Devices (formerly Linear Technology) is a 60V-input, constant-current/constant-voltage DC/DC converter with integrated 80V/3.5A N-channel MOSFET, designed for high-power LED driving in boost, SEPIC, buck-boost, and flyback topologies. It delivers ±3% current regulation and ±2% voltage regulation, supports 3000:1 True Color PWM™ dimming, and operates from –40°C to 125°C junction temperature.
For engineers reviewing the LT3955IUHE#PBF datasheet, LT3955IUHE#PBF pinout, LT3955IUHE#PBF application, or LT3955IUHE#PBF equivalent, key selection considerations include its rail-to-rail current sense range (0V–80V), programmable 100kHz–1MHz switching frequency, internal PWM generator with 4%–96% duty control, and open-LED fault reporting via VMODE.
Technical Context
The LT3955IUHE#PBF implements a fixed-frequency, current-mode architecture with dual-loop control: a high-gain transconductance error amplifier (VC) regulates either ISP–ISN differential voltage (for constant-current LED mode) or FB voltage (for constant-voltage mode). Its internal oscillator supports synchronization (SYNC pin) and features soft-start via DIM/SS pin charging current.
It integrates protection logic including ISP–ISN overcurrent detection (600mV threshold), FB overvoltage shutdown (VFB + 60mV), open-LED detection (FB < VFB – 50mV & ISP–ISN < 25mV), and thermal shutdown (>165°C). The PWMOUT pin serves both as buffered dimming output and fault indicator-driven low during FB overvoltage or ISP–ISN overcurrent events.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 60V - supports wide-range industrial and automotive supply rails without external pre-regulation. |
| Integrated Switch | 80V/3.5A N-channel MOSFET - eliminates external high-voltage switch; enables compact boost LED drivers up to 20W. |
| Current Sense Range | Rail-to-rail 0V to 80V - allows high-side or low-side sensing in any topology without level-shifting circuitry. |
| Dimming Ratio | 3000:1 True Color PWM™ - preserves LED color fidelity across full brightness range using externally synchronized or self-oscillating PWM. |
| Regulation Accuracy | ±3% constant-current, ±2% constant-voltage - ensures stable LED luminance and battery charge termination precision. |
| Switching Frequency | 100kHz to 1MHz (RT-programmable) - balances efficiency, EMI, and magnetics size; RT resistor sets exact operating point. |
| Operating Temperature | –40°C to 125°C (junction) - qualified for under-hood automotive, outdoor lighting, and industrial power systems. |
Pinout & Package
LT3955IUHE#PBF is housed in a thermally enhanced 36-lead (5mm × 6mm) plastic QFN package with two exposed pads: Pin 37 (GND) and Pin 38 (SW), both requiring solder connection to respective PCB copper planes for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ISP / ISN | High-side or low-side current sense inputs | Differential pair measuring LED current; supports 0V–80V common-mode range; bias current varies with CTRL voltage. |
| FB | Voltage feedback input | Regulates output voltage to 1.25V reference; enables CV mode and open-LED detection when combined with ISP/ISN monitoring. |
| CTRL | Analog dimming / current threshold control | Sets ISP–ISN regulation threshold from 20mV to 250mV linearly (0–1V), enabling precise analog dimming or temperature compensation. |
| PWM / PWMOUT | Digital dimming input / buffered output | PWM accepts 0–5V logic; PWMOUT drives external NFET for LED disconnect and asserts low on FB overvoltage or ISP–ISN overcurrent faults. |
| VMODE | Open-LED / CV-mode status flag | Open-drain output pulled low when FB drops below VFB – 50mV *and* ISP–ISN < 25mV - signals transition to voltage regulation or open-circuit condition. |
| DIM/SS | Soft-start timing & PWM generator control | Internal 12µA pull-up charges external capacitor; sets soft-start duration and self-oscillating PWM frequency/duty via charging current magnitude. |
| RT | Switching frequency programming | Resistor to GND sets oscillator frequency from 100kHz to 1MHz; enables optimization of efficiency vs. EMI vs. inductor size. |
| EN/UVLO | Enable & undervoltage lockout | 1.22V falling threshold with 40mV hysteresis; sub-µA shutdown current; enables reliable startup from weak supplies. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ Dimming | 3000:1 dimming ratio with no color shift - achieved via precise PWMOUT timing control and fast VC loop response preserving LED spectral stability. |
| Programmable Current Threshold | CTRL pin adjusts ISP–ISN regulation point from 20mV to 250mV - enables analog dimming, thermal derating, or C/10 battery charge termination. |
| Output Short-Circuit Protected Boost | ISP–ISN > 600mV triggers immediate SW shutdown and PWMOUT low assertion - protects LEDs, inductor, and MOSFET during load faults. |
| Open LED Detection & Reporting | VMODE pulls low when FB < VFB – 50mV *and* ISP–ISN < 25mV - provides system-level fault signaling without additional comparators or microcontroller polling. |
| Thermally Enhanced QFN | θJC = 3°C/W, θJA = 34°C/W - enables >20W LED drive in compact layout; exposed SW pad requires direct connection to switching node copper. |
Applications
| Automotive Headlamp Drivers | Industrial High-Bay LED Lighting |
|---|---|
|
Use Scenario: Driving 60V, 1.5A white LED strings in vehicle headlamps with strict EMI and thermal constraints. IC Role / Device Role / Timing Role: Constant-current controller with integrated 80V switch, synchronizable to vehicle clock to avoid AM band interference. Use Value: Eliminates external high-voltage MOSFET and gate driver; 3000:1 True Color PWM™ enables adaptive driving beam modulation without color distortion. |
Use Scenario: Powering 48V, 2A LED arrays in warehouse high-bay fixtures with 0–10V analog dimming interface. IC Role / Device Role / Timing Role: Dual-loop regulator operating in boost mode with CTRL-based analog dimming and FB-based overvoltage clamp. Use Value: ±3% current accuracy maintains consistent lumen output across line and temperature; rail-to-rail ISP/ISN sensing simplifies high-side current measurement. |
| Battery & Supercapacitor Chargers | UV-C LED Disinfection Systems |
|
Use Scenario: Charging 24V LiFePO₄ batteries or 30V supercapacitors from 12V–48V sources with C/10 termination. IC Role / Device Role / Timing Role: Constant-voltage regulator with C/10 indication via ISP–ISN threshold (25mV) and VMODE reporting. Use Value: Integrated C/10 detection replaces external current-sense amplifier and comparator; FB overvoltage protection prevents cell overcharge. |
Use Scenario: Driving pulsed 365nm UV-C LEDs at 100mA–500mA for surface disinfection with precise pulse-width control. IC Role / Device Role / Timing Role: Fast-response constant-current source with PWMOUT-driven external NFET for µs-level LED enable/disable. Use Value: 180ns minimum on/off times and 3000:1 dimming enable calibrated UVC dose delivery; open-LED detection prevents driver damage during LED failure. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3761EUHE#PBF | Higher 100V input rating; no integrated PWM generator; requires external PWM source for dimming. | Better suited for ultra-high-VIN LED strings (>60V); lacks self-oscillating dimming and VMODE reporting. | Select when VIN exceeds 60V or when external microcontroller controls all dimming functions. |
| LM3409QMHX/NOPB | 48V max VIN; no internal switch; requires external MOSFET; lower integration (no INTVCC LDO, no VMODE). | Cost-optimized for mid-power LED drivers; lacks open-LED reporting and True Color PWM™. | Select for cost-sensitive, non-automotive designs where 3000:1 dimming and fault reporting are not required. |
Compared with LT3955IUHE#PBF, LT3761EUHE#PBF offers higher input voltage tolerance but removes integrated dimming intelligence, while LM3409QMHX/NOPB reduces BOM count only by shifting complexity to external components - neither matches the LT3955IUHE#PBF's combination of 60V operation, self-contained PWM generation, and comprehensive LED protection.
Availability
LT3955IUHE#PBF is available at Aetrix Electronics and suitable for automotive headlamp drivers, industrial high-bay LED lighting, battery chargers, UV-C disinfection systems, and constant-current power supplies requiring stable component supply across extended temperature ranges.
Supply support for LT3955IUHE#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 acquired Linear Technology in 2017 and maintains its legacy of high-performance analog ICs for power management, signal conditioning, and precision conversion.
The LT3955IUHE#PBF belongs to Linear's LED driver product line, engineered specifically for high-reliability, high-dynamic-range solid-state lighting and power conversion where accurate current regulation, robust fault handling, and thermal resilience are critical.
FAQ
What is the maximum input voltage supported by the LT3955IUHE#PBF?
The LT3955IUHE#PBF supports a maximum input voltage of 60V, as specified in its Absolute Maximum Ratings. This allows direct operation from 48V industrial buses or automotive 36V nominal systems without pre-regulation. Exceeding 60V risks permanent damage per Note 1 in the datasheet. The device maintains full functionality across its 4.5V–60V operating range, including regulation accuracy and protection features.
How does the LT3955IUHE#PBF achieve 3000:1 True Color PWM™ dimming?
The LT3955IUHE#PBF achieves 3000:1 True Color PWM™ dimming through precise internal PWM generator timing and fast VC loop response. When driven by an external signal, the PWM pin accepts logic-level inputs and modulates the internal power switch with minimal jitter. The PWMOUT pin mirrors this signal with <35ns rise/fall times and drives external NFETs for clean LED enable/disable, preserving spectral output across the full dimming range without color shift.
Can the LT3955IUHE#PBF operate in constant-voltage mode for battery charging?
Yes, the LT3955IUHE#PBF can operate in constant-voltage mode for battery charging by configuring the FB pin as the voltage feedback input. With ISP and ISN tied together and CTRL set to VREF, the device regulates FB to 1.25V ±2%, enabling accurate CV charge termination. Its C/10 indication feature (via ISP–ISN threshold at 25mV) further supports Li-ion and supercapacitor charging profiles without external circuitry.
What is the purpose of the VMODE pin on the LT3955IUHE#PBF?
The VMODE pin on the LT3955IUHE#PBF is an open-drain status output that pulls low when two conditions occur simultaneously: FB voltage falls below VFB – 50mV *and* ISP–ISN differential drops below 25mV. This indicates either open-LED fault or transition from constant-current to constant-voltage regulation - useful for system-level fault reporting in LED drivers and battery chargers without requiring additional monitoring circuitry.
Does the LT3955IUHE#PBF require external compensation components?
Yes, the LT3955IUHE#PBF requires external RC compensation on the VC pin to stabilize the control loop. A capacitor between VC and GND sets dominant pole frequency, and adding a series resistor improves phase margin and transient response. Typical values range from 1nF–10nF capacitor with 1kΩ–10kΩ resistor, selected based on operating point and topology; the datasheet provides design guidelines and stability criteria for boost, SEPIC, and buck-boost configurations.
LT3955IUHE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Flyback, SEPIC, Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 4.5V
- Voltage - Supply (Max):
- 60V
- Voltage - Output:
- -
- Current - Output / Channel:
- 3.5A (Switch)
- Frequency:
- 100kHz ~ 1MHz
- Dimming:
- Analog, PWM
- Applications:
- -
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LT3955IUHE#PBF FAQ
1.How can I place an order for LT3955IUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3955IUHE#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 LT3955IUHE#PBF reliable?
The price and inventory of LT3955IUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3955IUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3955IUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3955IUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3955IUHE#PBF?
LT3955IUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3955IUHE#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 LT3955IUHE#PBF?
For technical support, including LT3955IUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3955IUHE#PBF requirements.
6.How does Aetrix verify that LT3955IUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3955IUHE#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 LT3955IUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3955IUHE#PBF?
All LT3955IUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3955IUHE#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 LT3955IUHE#PBF part is unused and in its original packaging.
Return procedure for LT3955IUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3955IUHE#PBF Tags
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