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Analog Devices Inc. LT3956EUHE#PBF
- Part No.:
- LT3956EUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3956EUHE#PBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3.3A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,164
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Product details
Overview
LT3956EUHE#PBF from Analog Devices (formerly Linear Technology) is a constant-current, constant-voltage DC/DC controller IC optimized for high-power LED driving in automotive headlamps and industrial lighting. It integrates an 84V/3.3A internal N-channel MOSFET, supports 4.5V–80V input, delivers up to 80V output, and enables true-color PWM dimming up to 3000:1. Its high-side current sensing architecture allows flexible boost, buck, buck-boost, SEPIC, or flyback topologies.
For engineers reviewing the LT3956EUHE#PBF datasheet, LT3956EUHE#PBF pinout, LT3956EUHE#PBF application, or LT3956EUHE#PBF equivalent, key selection criteria include its 250mV high-side current sense threshold, programmable 100kHz–1MHz switching frequency, open-LED protection via FB/VMODE, adjustable undervoltage lockout, and 36-lead 5mm × 6mm QFN package with exposed SW and GND pads.
Technical Context
The LT3956EUHE#PBF employs a fixed-frequency, current-mode control architecture with internal slope compensation, enabling stable regulation across wide VIN (4.5V–80V) and VOUT (up to 80V) ranges. Its dual-loop design simultaneously manages constant-current (via ISP/ISN differential sensing) and constant-voltage (via FB pin referenced to 1.25V) regulation, with automatic loop dominance arbitration.
High-side current sensing enables topology flexibility-boost, buck, buck-boost, SEPIC, or flyback-without ground-referenced LED strings. The CTRL pin linearly adjusts the current-sense threshold from 0mV to 250mV (0V–1.1V), while PWM input provides precise 3000:1 dimming and VMODE/PWMOUT pins deliver open-LED fault signaling and load disconnect capability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 80V - supports 12V/24V/48V systems and transient-tolerant automotive designs. |
| Output Voltage Capability | Up to 80V - enables long LED strings (e.g., 20+ white LEDs) without external boost stages. |
| Internal Switch Rating | 84V VDS, 3.3A continuous - eliminates need for external high-voltage MOSFET in most LED driver applications. |
| Current Sense Threshold | 250mV (adjustable down to 0mV via CTRL) - sets LED current with ±1% typical accuracy using standard shunt resistors. |
| Switching Frequency Range | 100kHz to 1MHz - allows optimization of inductor size, efficiency, and EMI performance. |
| Dimming Ratio | 3000:1 true-color PWM - preserves color consistency across full brightness range without flicker or color shift. |
| Package | 36-lead 5mm × 6mm QFN with exposed SW (Pin 38) and GND (Pin 37) pads - enables high-power thermal dissipation in compact layouts. |
Pinout & Package
LT3956EUHE#PBF is housed in a thermally enhanced 36-lead plastic QFN (5mm × 6mm) with two exposed pads: Pin 37 (GND) and Pin 38 (SW). Both must be soldered directly to PCB copper for electrical integrity and thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Input supply rail | Accepts 4.5V–80V; requires local 0.22µF bypass to PGND for stability. |
| SW | Drain of internal N-MOSFET | Connects to inductor; exposed pad (Pin 38) must be soldered to power plane for thermal conduction. |
| ISP / ISN | High-side current sense inputs | Differential pair measuring LED string current; common-mode range up to 80V, 250mV threshold default. |
| FB | Voltage feedback input | Regulates output voltage to 1.25V reference; enables open-LED detection and overvoltage protection. |
| CTRL | Current threshold adjustment | Linearly scales ISP–ISN threshold from 0mV to 250mV (0V–1.1V); used for analog dimming or thermal derating. |
| PWM | Digital dimming control | Active-low input enabling 3000:1 PWM dimming; drives PWMOUT synchronously. |
| VMODE | Open-LED status indicator | Open-collector output pulled low when FB drops below 1.20V - signals CV mode activation or open-circuit fault. |
| PWMOUT | Load disconnect driver | Buffered PWM signal referenced to INTVCC; drives external NFET to isolate LED string during overvoltage events. |
| EN/UVLO | Enable and undervoltage lockout | 1.22V falling threshold with user-programmable hysteresis; shuts down IC below safe VIN level. |
| RT | Frequency programming | Resistor-to-GND sets switching frequency from 100kHz to 1MHz per datasheet curve. |
| SS | Soft-start control | External capacitor sets startup ramp time; reset by UVLO or thermal fault. |
| VC | Error amplifier output | High-impedance node storing demand current state; requires RC compensation network for loop stability. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 84V/3.3A N-MOSFET | Reduces BOM count and layout complexity for high-voltage LED drivers; eliminates gate driver and external FET. |
| High-side current sensing | Enables all topologies (boost/buck/SEPIC/flyback) without compromising LED string grounding or requiring isolated sense amplifiers. |
| True-color 3000:1 PWM dimming | Maintains consistent LED chromaticity across full dimming range - critical for automotive headlamp compliance and display backlighting. |
| Programmable open-LED protection | Uses FB voltage monitoring and VMODE pull-down to detect open circuits and disable switching before overvoltage damage occurs. |
| Adjustable current threshold (0–250mV) | Allows analog dimming, temperature-based current derating, or adaptive power scaling via CTRL pin voltage. |
Applications
| Automotive Headlamp Driver | Battery-Powered High-Brightness Lighting |
|---|---|
Use Scenario: Driving 25W white LED arrays in vehicle forward lighting with strict thermal and EMI constraints. IC Role / Device Role / Timing Role: Constant-current controller managing boost topology with 3000:1 PWM dimming and open-LED fault reporting via VMODE. Use Value: Delivers 94% peak efficiency at 25W, meets automotive transient immunity (80V), and ensures fail-safe operation during LED string breakage. | Use Scenario: Powering portable searchlights or emergency lighting from 12V–48V battery banks with variable load conditions. IC Role / Device Role / Timing Role: Buck-boost LED driver maintaining regulated current despite wide input voltage swing and load changes. Use Value: Supports 4.5V–80V input range and programmable UVLO, enabling reliable operation across partially discharged batteries and cold-cranking conditions. |
| Industrial Machine Vision Illumination | Architectural LED String Controller |
Use Scenario: Driving high-current, color-stable LED arrays for precision imaging systems requiring strobed illumination. IC Role / Device Role / Timing Role: Fast-response constant-current source with synchronized PWMOUT-driven load disconnect for microsecond-level exposure control. Use Value: Enables <200ns PWMOUT rise/fall times and sub-microsecond fault response, eliminating image blur during high-speed camera capture. | Use Scenario: Controlling long series-connected LED strings in commercial building façade lighting with remote dimming and fault monitoring. IC Role / Device Role / Timing Role: SEPIC topology LED driver with FB-based open-circuit detection and CTRL-based thermal derating for ambient temperature compensation. Use Value: Provides scalable current regulation across 10–80V output, integrated short-circuit protection for ISP/ISN, and programmable soft-start to prevent inrush stress on long cables. |
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 | No integrated switch; requires external high-side N-MOSFET; supports higher output voltages (100V+). | Better suited for ultra-high-VOUT (>80V) or multi-string parallel configurations where discrete FET selection is needed. | Select LTC3783EFE#PBF only when >80V output or custom FET optimization is required; LT3956EUHE#PBF offers lower BOM cost and simpler layout for ≤80V applications. |
| LM3410XSD/NOPB | Lower voltage rating (42V max VIN); 1.5A switch; fixed 1.6MHz frequency; no CTRL-based analog dimming. | Targeted at low-power portable LED lighting (<5W), not suitable for automotive or industrial high-brightness use cases. | LM3410XSD/NOPB is not a functional substitute for LT3956EUHE#PBF due to insufficient voltage/current capability and missing features like open-LED protection and topology flexibility. |
Compared with LTC3783EFE#PBF and LM3410XSD/NOPB, the LT3956EUHE#PBF uniquely combines integrated 84V/3.3A switching, high-side sensing, 3000:1 PWM dimming, and dual CC/CV regulation in a single 5mm × 6mm QFN - making it the only drop-in solution for 25W+ automotive LED headlamp designs requiring minimal external components and robust fault handling.
Availability
LT3956EUHE#PBF is available at Aetrix Electronics and suitable for automotive lighting, industrial machine vision systems, and battery-powered high-brightness LED applications requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3956EUHE#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, formed through the acquisition of Linear Technology in 2017.
The LT3956EUHE#PBF belongs to ADI's Power by Linear™ LED driver product line, designed specifically for high-efficiency, high-reliability constant-current LED control in demanding environments including automotive, industrial, and architectural lighting.
FAQ
What is the maximum LED string voltage supported by the LT3956EUHE#PBF?
The LT3956EUHE#PBF supports output voltages up to 80V, enabling drive of long LED strings - for example, 20+ white LEDs (3.2V each) or 10+ high-voltage COB LEDs. This limit is defined by the absolute maximum rating of the internal 84V MOSFET and the voltage handling capability of the ISP/ISN current sense inputs (up to 80V common-mode). Operation beyond 80V risks permanent device damage and is not supported.
How does the LT3956EUHE#PBF implement open-LED protection?
The LT3956EUHE#PBF implements open-LED protection using the FB pin and VMODE output. When the LED string opens, FB voltage rises above its 1.25V regulation threshold. Once FB exceeds VFB – 50mV (≈1.20V), the VMODE pin pulls low - signaling an open-circuit condition. If FB rises further to exceed VFB + 60mV (≈1.31V), the PWMOUT pin is forced low, disconnecting the LED load via an external NFET. This dual-threshold scheme prevents overvoltage damage while providing early fault indication.
Can the LT3956EUHE#PBF operate in buck mode with a grounded LED cathode?
Yes, the LT3956EUHE#PBF supports buck-mode operation with a grounded LED cathode using the configuration shown in Figure 3 of the datasheet. In this setup, the ISP/ISN pair senses current on the high side of the LED string, while FB monitors a level-shifted voltage derived from the output via resistor divider. This maintains accurate constant-current regulation without requiring the LED string to float, and leverages the IC's inherent high-side sensing architecture for optimal noise immunity and layout simplicity.
What is the role of the CTRL pin on the LT3956EUHE#PBF, and how is it used in practice?
The CTRL pin on the LT3956EUHE#PBF adjusts the ISP–ISN current sense threshold from 0mV to 250mV. At CTRL = 2V (tied to VREF), the threshold is fixed at 250mV for full-scale current regulation. Below 1.1V, the threshold scales linearly (e.g., CTRL = 0.5V → ~100mV), enabling analog dimming or thermal derating. In practice, CTRL is often tied to a thermistor divider for LED temperature compensation or to a DAC for programmable current control - all without modifying the main PWM dimming signal.
Does the LT3956EUHE#PBF require external components for soft-start, and how is it configured?
Yes, the LT3956EUHE#PBF uses an external capacitor on the SS pin to configure soft-start. A typical value is 1nF–10nF, which sets the ramp time for both oscillator frequency and VC clamp voltage. The SS pin has a 10µA internal pull-up current source to a 2.5V rail, so the capacitor charges linearly. Soft-start duration is approximately tSS ≈ (CSS × 2.5V) / 10µA. The SS pin is automatically reset to GND during EN/UVLO undervoltage events or thermal shutdown, ensuring controlled restart after faults.
LT3956EUHE#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):
- 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)
LT3956EUHE#PBF FAQ
1.How can I place an order for LT3956EUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3956EUHE#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 LT3956EUHE#PBF reliable?
The price and inventory of LT3956EUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3956EUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3956EUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3956EUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3956EUHE#PBF?
LT3956EUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3956EUHE#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 LT3956EUHE#PBF?
For technical support, including LT3956EUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3956EUHE#PBF requirements.
6.How does Aetrix verify that LT3956EUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3956EUHE#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 LT3956EUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3956EUHE#PBF?
All LT3956EUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3956EUHE#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 LT3956EUHE#PBF part is unused and in its original packaging.
Return procedure for LT3956EUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3956EUHE#PBF Tags
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