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Analog Devices Inc. LT3956IUHE#TRPBF
- Part No.:
- LT3956IUHE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3956IUHE#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3.3A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,066
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Product details
Overview
LT3956IUHE#TRPBF from Analog Devices (formerly Linear Technology) is a constant-current/constant-voltage DC/DC controller IC designed for high-power LED driving in automotive, industrial, and architectural lighting. It integrates an 84V/3.3A internal N-channel MOSFET, supports 4.5V–80V input and up to 80V output, delivers true-color PWM dimming up to 3000:1, and operates in boost, buck, buck-boost, SEPIC, or flyback topologies.
For engineers reviewing the LT3956IUHE#TRPBF datasheet, LT3956IUHE#TRPBF pinout, LT3956IUHE#TRPBF application, or LT3956IUHE#TRPBF equivalent, key selection considerations include high-side current sensing capability, programmable switching frequency (100kHz–1MHz), open-LED and overvoltage protection, adjustable current threshold via CTRL pin, and thermal shutdown at 165°C - all critical for robust LED driver design and BOM optimization.
Technical Context
The LT3956IUHE#TRPBF implements a fixed-frequency, current-mode control architecture with dual-loop regulation: a high-side current sense amplifier (250mV full-scale threshold) governs constant-current operation, while a ground-referenced FB pin (1.232V nominal regulation voltage) enables constant-voltage mode and open-LED fault detection. Its internal 7.15V INTVCC LDO powers gate drivers and logic.
Switching is managed by an internal N-channel MOSFET (84V VDS, 3.3A continuous, 3.9A typical current limit) with minimum on-time of 200ns and off-time of 170ns. Protection features include ISP/ISN short-circuit detection (<3V common-mode), VMODE status reporting, PWMOUT-driven load disconnect, and programmable UVLO with hysteresis on EN/UVLO.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 80V - supports wide-range battery and industrial supplies, including 12V/24V/48V systems with 80V transient tolerance. |
| Output Voltage Capability | Up to 80V - enables direct drive of long LED strings in boost or SEPIC configurations without external HV FETs. |
| Internal Switch Rating | 84V VDS, 3.3A continuous - eliminates need for external high-voltage switch in most medium-power LED applications. |
| Current Sense Threshold | 250mV (adjustable down to 0mV via CTRL pin) - enables precise, scalable LED current regulation with minimal power loss in sense resistor. |
| Switching Frequency Range | 100kHz to 1MHz - allows optimization of magnetic size, efficiency, and EMI performance using RT resistor. |
| Dimming Ratio | 3000:1 true-color PWM - preserves LED chromaticity across full brightness range, critical for automotive headlamps and display backlighting. |
| Operating Junction Temp | –40°C to +125°C - qualified for under-hood automotive and harsh industrial environments. |
Pinout & Package
LT3956IUHE#TRPBF is housed in a thermally enhanced 36-lead (5mm × 6mm) plastic QFN package with two exposed pads: Pin 37 (GND) and Pin 38 (SW). The SW pad must be soldered directly to the PCB's high-current switch node; GND pad requires low-impedance connection to system ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input supply rail input | Accepts 4.5V–80V; requires local 0.22µF+ ceramic bypass to PGND. |
| SW | Drain of internal N-MOSFET | Connects to inductor; exposed pad (Pin 38) must be soldered to PCB switch node. |
| ISP / ISN | High-side LED current sense inputs | Differential pair referenced to >2.9V common-mode; enables topology-flexible current regulation. |
| FB | Voltage loop feedback input | Regulates to 1.232V; used for CV mode, open-LED detection, and overvoltage protection. |
| CTRL | Current threshold adjustment | Linearly scales sense threshold from 0mV to 250mV - enables analog dimming and thermal derating. |
| PWM | Digital dimming control | Active-high input; enables 3000:1 PWM dimming and forces VC into high-impedance storage state when low. |
| VMODE | Open-LED / CV mode status | Open-collector output pulled low when FB drops ≤4% below regulation - signals fault or CV takeover. |
| PWMOUT | Buffered PWM signal output | Drives external NFET disconnect switch; forced low during FB overvoltage (>1.31V) to isolate LED load. |
| RT | Frequency programming | Resistor-to-GND sets switching frequency from 100kHz to 1MHz per datasheet curve. |
| SS | Soft-start control | Capacitor-to-GND sets soft-start time; reset by UVLO or thermal fault. |
| EN/UVLO | Enable & undervoltage lockout | 1.22V falling threshold with user-programmable hysteresis; <1µA shutdown current. |
| INTVCC | Internal LDO output | 7.15V regulated supply for gate drivers; requires 4.7µF ceramic bypass close to pin. |
| VC | Error amplifier output | Transconductance output for loop compensation; high-Z during PWM low for state retention. |
| GND / PGND | Signal & power ground returns | GND (Pin 1) and PGND (Pins 12–17) must be Kelvin-connected to minimize noise coupling into sense path. |
Key Features
| Feature | Design Value |
|---|---|
| Topology Flexibility | Supports boost, buck, buck-boost, SEPIC, and flyback - enables single IC reuse across diverse LED voltage/current requirements. |
| High-Side Current Sensing | Enables accurate current regulation regardless of LED string grounding - essential for isolated or floating-load designs. |
| Integrated Protection Suite | Includes open-LED detection (via FB), overvoltage shutdown (via PWMOUT), short-circuit sensing (ISP/ISN <3V), and thermal shutdown (165°C). |
| Programmable Dimming | Combines 3000:1 PWM dimming with analog dimming via CTRL pin - supports hybrid dimming schemes for flicker-free operation. |
| Robust Power Management | INTVCC LDO with 4.1V UVLO, 14mA current limit, and <12µA shutdown draw - ensures reliable startup and low-power standby. |
Applications
| Automotive Headlamp Driver | Industrial High-Bay Lighting |
|---|---|
Use Scenario: 25W white LED headlamp in 12V vehicle system with 80V load dump transients. IC Role / Device Role / Timing Role: Constant-current controller regulating 700mA LED string in boost configuration; manages thermal foldback and open-circuit fault reporting via VMODE. Use Value: Delivers 94% peak efficiency at 25W, withstands automotive transients up to 80V, and maintains color fidelity across full 3000:1 dimming range. | Use Scenario: 48V-input, 60V-output LED fixture for warehouse lighting with analog + PWM dimming. IC Role / Device Role / Timing Role: Buck-boost controller maintaining 1.2A constant current across varying line and load conditions; uses CTRL pin for temperature-compensated dimming. Use Value: Eliminates need for external HV switch; enables seamless transition between dimming modes without color shift or audible noise. |
| Battery-Powered Emergency Light | Architectural Accent Lighting |
Use Scenario: Portable emergency light powered by 3S Li-ion (9–12.6V) driving 36V LED string. IC Role / Device Role / Timing Role: Boost converter with programmable UVLO (EN/UVLO) and soft-start (SS) to prevent inrush; uses PWMOUT to disconnect load during fault. Use Value: Achieves >90% efficiency across battery discharge curve; provides fail-safe open-LED detection and automatic shutdown. | Use Scenario: Low-noise, high-CRI RGBW accent lighting with independent channel control. IC Role / Device Role / Timing Role: Constant-current source in SEPIC topology enabling floating LED cathode/anode; leverages high-side sensing for ground-referenced control interface. Use Value: Enables compact, transformerless design with precise current matching across channels and immunity to ground loop interference. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#PBF | Requires external high-side N-MOSFET; no integrated switch; supports higher output voltages (100V+); lacks built-in PWMOUT disconnect driver. | Better suited for >80V LED strings or ultra-high-efficiency discrete designs where thermal management of external FET is preferred. | Select LTC3783EFE#PBF only when output voltage exceeds 80V or when discrete FET selection is required for specific RDS(on)/Qg trade-offs. |
| LM3410XSD/NOPB | Single-ended boost-only controller; 40V max input; 1.5A switch; no high-side sensing; no VMODE/PWMOUT protection outputs. | Targeted at low-power (<10W), cost-sensitive consumer lighting - lacks automotive-grade protection and multi-topology flexibility. | Choose LM3410XSD/NOPB only for simple, low-voltage boost LED drivers where open-LED reporting and 80V tolerance are unnecessary. |
Compared with LTC3783EFE#PBF and LM3410XSD/NOPB, the LT3956IUHE#TRPBF uniquely combines integrated 84V/3.3A switching, high-side current sensing, dual-loop CV/CC regulation, and dedicated fault-reporting pins - making it the optimal choice for robust, space-constrained, medium-power LED systems requiring automotive or industrial reliability.
Availability
LT3956IUHE#TRPBF is available at Aetrix Electronics and suitable for automotive lighting, industrial high-bay fixtures, and battery-powered emergency lighting requiring stable component supply, extended temperature operation (–40°C to +125°C), and AEC-Q200-aligned reliability.
Supply support for LT3956IUHE#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3956IUHE#TRPBF belongs to ADI's Power by Linear™ LED driver portfolio, engineered specifically for high-reliability, high-efficiency constant-current LED applications demanding wide input range, topology flexibility, and comprehensive protection - especially in automotive and industrial settings.
FAQ
What is the maximum LED string voltage supported by the LT3956IUHE#TRPBF?
The LT3956IUHE#TRPBF supports output voltages up to 80V, enabling direct drive of long LED strings in boost, SEPIC, or flyback configurations. This rating is validated across the full –40°C to +125°C operating junction temperature range and accounts for safe margin against transients. Exceeding 80V risks violating absolute maximum ratings and may trigger overvoltage protection via the FB pin.
Does the LT3956IUHE#TRPBF require an external MOSFET for operation?
No, the LT3956IUHE#TRPBF integrates a fully rated 84V/3.3A N-channel power MOSFET, eliminating the need for an external high-voltage switch in most medium-power LED applications. External FETs are only required for output currents exceeding 3.3A continuous or output voltages above 80V - scenarios where the LT3956IUHE#TRPBF would operate as a controller rather than a complete solution.
How does the CTRL pin affect LED current regulation in the LT3956IUHE#TRPBF?
The CTRL pin on the LT3956IUHE#TRPBF linearly adjusts the high-side current sense threshold from 0mV to 250mV. At CTRL ≥1.2V, full-scale 250mV threshold applies (ILED = 250mV/RLED). Below 1V, ILED = (VCTRL – 100mV)/(4 × RLED), enabling analog dimming down to near-zero current. This function also supports thermal derating when paired with an NTC thermistor.
Can the LT3956IUHE#TRPBF detect an open LED string?
Yes, the LT3956IUHE#TRPBF detects open LED strings via its FB pin: when FB rises above the regulation threshold (1.232V) minus 50mV, the VMODE pin pulls low to signal fault condition. Simultaneously, if FB exceeds 1.232V + 60mV, PWMOUT is driven low to disconnect the LED load via an external NFET - preventing overvoltage damage. These functions operate independently of PWM state.
What package and thermal characteristics define the LT3956IUHE#TRPBF?
The LT3956IUHE#TRPBF uses a 36-lead 5mm × 6mm plastic QFN with two exposed thermal pads: Pin 37 (GND) and Pin 38 (SW). Its θJA is 43°C/W and θJC is 5°C/W. Proper PCB layout - including soldering both exposed pads to large copper planes - is essential to maintain junction temperature ≤125°C under full load, especially in automotive or enclosed industrial enclosures.
LT3956IUHE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 36-WFQFN, 28 Leads, Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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):
- 80V
- Voltage - Output:
- 80V
- Current - Output / Channel:
- 3.3A (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)
LT3956IUHE#TRPBF FAQ
1.How can I place an order for LT3956IUHE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3956IUHE#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 LT3956IUHE#TRPBF reliable?
The price and inventory of LT3956IUHE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3956IUHE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3956IUHE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3956IUHE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3956IUHE#TRPBF?
LT3956IUHE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3956IUHE#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 LT3956IUHE#TRPBF?
For technical support, including LT3956IUHE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3956IUHE#TRPBF requirements.
6.How does Aetrix verify that LT3956IUHE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3956IUHE#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 LT3956IUHE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3956IUHE#TRPBF?
All LT3956IUHE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3956IUHE#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 LT3956IUHE#TRPBF part is unused and in its original packaging.
Return procedure for LT3956IUHE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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