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Analog Devices Inc. LT3954IUHE#PBF
- Part No.:
- LT3954IUHE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3954IUHE#PBF.pdf
- Description:
- IC LED DRIVER RGLTR PWM 5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,529
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Product details
Overview
LT3954IUHE#PBF from Analog Devices (formerly Linear Technology) is a 40V input, constant-current/constant-voltage DC/DC LED controller with integrated 40V/5A N-channel MOSFET, programmable 100kHz–1MHz switching frequency, ±3% current regulation, and 3000:1 True Color PWM™ dimming. It drives high-power LEDs in boost, buck-boost, SEPIC, Cuk, or flyback topologies and supports battery/supercapacitor charging.
For engineers reviewing the LT3954IUHE#PBF datasheet, LT3954IUHE#PBF pinout, LT3954IUHE#PBF application, or LT3954IUHE#PBF equivalent, key selection considerations include high-side/low-side current sensing capability, rail-to-rail 0V–40V sense range, open-LED and short-circuit protection, analog dimming via CTRL pin, and thermally enhanced 36-lead QFN package with dual exposed pads (GND and SW).
Technical Context
The LT3954IUHE#PBF implements a fixed-frequency, current-mode control architecture with internal slope compensation, enabling stable operation across wide VIN (4.5V–40V) and output voltage ranges. Its dual-loop design simultaneously monitors ISP–ISN for constant-current regulation (±3%) and FB for constant-voltage regulation (±2%), with automatic mode transition signaled via VMODE.
It integrates a self-oscillating PWM generator (programmable 4%–96% duty, 300Hz–390Hz) driven by DIM/SS current, plus external PWM input support for up to 3000:1 dimming. The internal 7.85V LDO (INTVCC) powers gate drivers and logic, with 30mA current limit and 4.1V UVLO.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4.5V to 40V - supports automotive battery, industrial 24V, and wide-input LED systems without pre-regulation. |
| Internal Switch | 40V/5A N-channel MOSFET - eliminates external high-voltage switch; enables compact boost LED drivers up to 20W. |
| Current Regulation Accuracy | ±3% - ensures consistent LED brightness across temperature and line/load variations. |
| Switching Frequency Range | 100kHz to 1MHz - allows optimization of inductor size, efficiency, and EMI filtering per application. |
| PWM Dimming Ratio | 3000:1 True Color PWM™ - preserves color fidelity in high-end architectural and display lighting. |
| Current Sense Range | Rail-to-rail 0V to 40V - enables high-side or low-side sensing in any topology without level-shifting circuitry. |
| Package | 36-lead (5mm × 6mm) QFN with dual exposed pads - provides low θJC = 3°C/W thermal path for SW and GND planes. |
Pinout & Package
LT3954IUHE#PBF uses a thermally enhanced 36-lead plastic QFN (5mm × 6mm) with two exposed pads: Pin 37 (GND) and Pin 38 (SW), both requiring direct soldering to 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–40V common-mode range and ±3% regulation accuracy. |
| FB | Voltage feedback input | Regulates output voltage to 1.25V reference; enables CV mode, open-LED detection, and overvoltage protection. |
| CTRL | Analog dimming / current threshold control | Adjusts ISP–ISN threshold from 20mV to 268mV linearly (0–1V), enabling precise analog dimming and thermal derating. |
| DIM/SS | Soft-start and PWM generator programming | Sets soft-start time and PWMOUT duty ratio (4%–96%) via external capacitor and internal 12µA pull-up current. |
| RT | Switching frequency adjustment | Resistor-to-GND sets frequency from 100kHz–1MHz; enables EMI tuning and inductor size optimization. |
| VMODE | Open-LED / CV-mode status indicator | Open-drain output pulled low when FB ≥ VFB − 50mV AND ISP−ISN ≤ 25mV - signals transition to voltage regulation. |
| PWMOUT | Buffered PWM output | Drives external NMOS disconnect FET; toggles low during FB overvoltage (> VFB + 60mV) for LED protection. |
| EN/UVLO | Enable and undervoltage lockout | 1.22V falling threshold with 40mV hysteresis; sub-µA shutdown current (<1µA) when pulled ≤ 0.4V. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ dimming | 3000:1 ratio with no color shift - critical for RGB LED systems and high-CRI lighting where spectral consistency matters. |
| Programmable switching frequency | 100kHz–1MHz via RT resistor - balances efficiency, component size, and EMI compliance without redesigning layout. |
| Rail-to-rail current sense range | 0V to 40V common-mode - eliminates need for level-shifters or dedicated high-side sense ICs in boost/buck-boost designs. |
| Integrated 7.85V LDO (INTVCC) | 30mA current-limited, 4.1V UVLO - powers internal drivers reliably while preventing MOSFET under-enhancement at low VIN. |
| Output protection suite | Open-LED reporting (VMODE), short-circuit protected boost, ISP–ISN overcurrent (600mV), and FB overvoltage shutdown - reduces external fault-handling components. |
| Thermally optimized QFN | θJC = 3°C/W for SW pad, θJA = 34°C/W - sustains 20W LED drive in compact industrial or automotive enclosures without forced air. |
Applications
| Automotive Headlamp Drivers | Industrial High-Bay LED Lighting |
|---|---|
Use Scenario: Driving 3–5 series high-brightness white LEDs (32V, 650mA) from 12V/24V vehicle battery with cold-crank tolerance down to 4.5V. IC Role / Device Role / Timing Role: Constant-current LED controller with boost topology, integrated switch, and 3000:1 PWM dimming for adaptive driving beam control. Use Value: Eliminates external MOSFET and gate driver; maintains ±3% current accuracy across –40°C to 125°C ambient; VMODE reports open-circuit LED faults to vehicle ECU. |
Use Scenario: Powering 48V, 1.2A LED strings in warehouse lighting using 48V DC distribution bus with surge immunity. IC Role / Device Role / Timing Role: Buck-boost LED driver supporting wide input (36–57V) and precise current regulation with analog dimming via 0–10V control signal. Use Value: Rail-to-rail 0–40V ISP–ISN sensing enables direct low-side sensing; INTVCC LDO ensures robust gate drive during line transients; 95% peak efficiency reduces thermal load. |
| Battery & Supercapacitor Chargers | Medical Surgical Lighting |
Use Scenario: Charging 24V LiFePO₄ battery packs or 25V supercapacitor banks from 12–40V sources with C/10 termination and voltage limiting. IC Role / Device Role / Timing Role: Constant-current/constant-voltage regulator with programmable charge profile, C/10 indication via VMODE, and overvoltage cutoff. Use Value: Uses same FB and ISP–ISN loops for CC/CV transition; ±2% voltage regulation prevents overcharge; open-LED detection repurposed as end-of-charge flag. |
Use Scenario: Driving color-mixed RGBW LED arrays in surgical headlamps requiring flicker-free, calibrated dimming and zero color shift. IC Role / Device Role / Timing Role: Multi-channel LED controller (per channel) with True Color PWM™ dimming and analog fine-tuning via CTRL pin for white-point stability. Use Value: 3000:1 PWM dimming avoids low-frequency flicker; ±3% current matching between channels ensures consistent chromaticity; low noise VC loop minimizes optical ripple. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3761EUHE#PBF | Higher 60V input rating, no integrated PWM generator, requires external PWM source for dimming. | Better suited for 48V industrial LED systems needing >40V VIN; lacks self-oscillating dimming, so needs external timing circuitry. | Choose LT3761EUHE#PBF when input exceeds 40V or when external PWM synchronization is preferred over internal generator. |
| LM3409HVMM/NOPB | 48V max VIN, no integrated PWM generator, 1.25V FB reference, no VMODE or C/10 reporting. | Cost-optimized for basic boost LED drivers; lacks open-LED status reporting and analog dimming flexibility of CTRL pin. | Choose LM3409HVMM/NOPB for simpler, lower-cost designs where 3000:1 dimming and fault reporting are not required. |
Compared with LT3954IUHE#PBF, LT3761EUHE#PBF offers higher input voltage margin but requires external dimming control, while LM3409HVMM/NOPB reduces BOM count at the expense of dimming fidelity and diagnostic capability - making LT3954IUHE#PBF optimal for high-reliability, feature-rich LED and charging applications.
Availability
LT3954IUHE#PBF is available at Aetrix Electronics and suitable for automotive headlamp drivers, industrial high-bay LED lighting, and battery/supercapacitor charging systems requiring stable component supply, extended temperature operation, and long-term lifecycle support.
Supply support for LT3954IUHE#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 power management ICs with rigorous automotive and industrial qualification.
The LT3954IUHE#PBF belongs to Linear's LED controller product line, designed specifically for high-efficiency, high-reliability constant-current LED drivers and multi-mode battery chargers operating across harsh environments.
FAQ
What is the maximum output power achievable with the LT3954IUHE#PBF in boost configuration?
The LT3954IUHE#PBF supports up to 20W output in typical boost LED applications, as validated in the datasheet's "95% Efficiency 20W Boost LED Driver" reference design. This assumes 24V input, 32V LED string, and 650mA current - constrained by the 5A internal MOSFET, thermal limits of the 5mm × 6mm QFN package, and efficiency derating above 1MHz switching frequency. Higher power requires external switch or parallel configurations.
Does the LT3954IUHE#PBF support high-side current sensing, and what is the common-mode voltage range?
Yes, the LT3954IUHE#PBF supports true high-side current sensing via the ISP and ISN pins, with a rail-to-rail common-mode input range of 0V to 40V. This allows placement of the sense resistor on the high side of the LED string - essential for buck, SEPIC, and Cuk topologies where low-side sensing is impractical. The datasheet confirms operation up to VIN = 40V with full accuracy.
How does the VMODE pin function in open-LED detection, and what external components are needed?
The VMODE pin asserts a low-level open-drain signal when FB ≥ (VFB − 50mV) AND (ISP − ISN) ≤ 25mV - indicating loss of LED current and transition to constant-voltage regulation. An external pull-up resistor (typically to INTVCC) is mandatory. No additional components are required; the condition is internally generated and latched during PWM high periods, providing reliable fault reporting without external comparators.
Can the LT3954IUHE#PBF be used for constant-voltage regulation only, without LED current control?
Yes, the LT3954IUHE#PBF can operate exclusively in constant-voltage mode by tying ISP and ISN together and connecting CTRL to VREF (2V), which disables the current loop. The FB pin then regulates output voltage to 1.25V ±2%, enabling use as an accurate CV supply for battery charging or general-purpose DC/DC conversion - retaining all protections including FB overvoltage shutdown and thermal limiting.
What is the purpose of the dual exposed pads (Pin 37 and Pin 38) on the LT3954IUHE#PBF QFN package?
Pin 37 (exposed pad) is electrically GND and must be soldered to the PCB ground plane for low-inductance return path and thermal dissipation. Pin 38 (exposed pad) is electrically SW (switch node) and must be soldered to the SW copper pour - isolating high-dI/dt switching currents from the main GND plane. This dual-pad construction achieves θJC = 3°C/W for SW and improves EMI performance by separating power and signal ground paths.
LT3954IUHE#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):
- 40V
- Voltage - Output:
- -
- Current - Output / Channel:
- 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)
LT3954IUHE#PBF FAQ
1.How can I place an order for LT3954IUHE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3954IUHE#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 LT3954IUHE#PBF reliable?
The price and inventory of LT3954IUHE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3954IUHE#PBF is usually 5 days.
3.What payment methods are accepted for LT3954IUHE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3954IUHE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3954IUHE#PBF?
LT3954IUHE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3954IUHE#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 LT3954IUHE#PBF?
For technical support, including LT3954IUHE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3954IUHE#PBF requirements.
6.How does Aetrix verify that LT3954IUHE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3954IUHE#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 LT3954IUHE#PBF meets industry standards.
7.What is the process for return or replacement of LT3954IUHE#PBF?
All LT3954IUHE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3954IUHE#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 LT3954IUHE#PBF part is unused and in its original packaging.
Return procedure for LT3954IUHE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3954IUHE#PBF Tags
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