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Analog Devices Inc. LT3954IUHE#TRPBF
- Part No.:
- LT3954IUHE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 36-WFQFN, 28 Leads, Exposed Pad
- Datasheet:
-
LT3954IUHE#TRPBF.pdf
- Description:
- IC LED DRIVER RGLTR PWM 5A 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,481
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Product details
Overview
LT3954IUHE#TRPBF from Analog Devices (formerly Linear Technology) is a 40V input, constant-current/constant-voltage DC/DC converter with integrated 40V/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 100kHz–1MHz switching frequency, and enables 3000:1 True Color PWM™ dimming. It is used in automotive exterior lighting and industrial high-brightness LED arrays.
For engineers reviewing the LT3954IUHE#TRPBF datasheet, LT3954IUHE#TRPBF pinout, LT3954IUHE#TRPBF application, or LT3954IUHE#TRPBF equivalent, key selection criteria include high-side/low-side current sensing capability, rail-to-rail 0V–40V sense range, programmable soft-start via DIM/SS pin, open-LED fault reporting via VMODE, and thermal protection with 125°C junction limit.
Technical Context
The LT3954IUHE#TRPBF 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 manages ISP/ISN-based constant-current regulation (with CTRL-adjustable threshold from 20mV to 268mV) and FB-based constant-voltage regulation (1.25V reference).
It integrates an internal 7.85V LDO (INTVCC) powering gate drivers and logic, supports external synchronization via SYNC pin, and features dedicated protection circuits: ISP–ISN overcurrent detection at 600mV, FB overvoltage shutdown (>VFB + 60mV), and VMODE open-LED reporting (FB < VFB – 50mV & ISP–ISN < 25mV). The PWMOUT pin provides buffered dimming control and fault signaling.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 40V - supports 12V/24V/36V industrial and automotive rails without pre-regulation |
| Switch Rating | 40V/5A N-channel MOSFET - enables single-stage boost up to ~32V LED string at 650mA (20W) |
| Current Sense Range | Rail-to-rail 0V to 40V - allows high-side or low-side sensing in any topology without level-shifting |
| Regulation Accuracy | ±3% constant-current, ±2% constant-voltage - ensures consistent LED brightness and battery charge termination |
| Dimming Capability | 3000:1 True Color PWM™ + analog dimming via CTRL - preserves color fidelity across full intensity range |
| Switching Frequency | Programmable 100kHz–1MHz via RT resistor - balances efficiency, EMI, and magnetics size |
| Thermal Package | 36-lead 5mm × 6mm QFN with exposed SW and GND pads - achieves θJC = 3°C/W for high-power dissipation |
Pinout & Package
LT3954IUHE#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), 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 via external sense resistor; supports 0V–40V common-mode range |
| FB | Voltage feedback input | Connects to LED string cathode or battery terminal to enable constant-voltage regulation or open-LED detection |
| CTRL | Analog dimming and current threshold control | Sets ISP–ISN regulation point from 20mV to 268mV linearly (0–1V) or fixed full-scale (≥1.2V) |
| DIM/SS | Soft-start timing and PWM generator programming | Charging current sets PWMOUT duty cycle; capacitor value defines soft-start duration and dimming frequency |
| VMODE | Open-LED status indicator | Open-drain output pulled low when FB drops below VFB – 50mV and ISP–ISN < 25mV - signals transition to CV mode or fault |
| PWMOUT | Buffered PWM dimming output | Drives external NMOS disconnect switch; forced low during FB overvoltage or ISP–ISN overcurrent faults |
| SW | Internal MOSFET drain | High-current switching node; must be connected to exposed pad (Pin 38) and routed with minimal loop area |
| INTVCC | Internally regulated 7.85V supply | Powers gate drivers and internal logic; requires local 1µF ceramic bypass to GNDK/PGND |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ Dimming | 3000:1 dimming ratio with no color shift - achieved via precise internal PWM generator synchronized to external clock or self-oscillating mode |
| Topology Flexibility | Supports boost, SEPIC, Cuk, buck, buck-boost, and flyback - enabled by independent ISP/ISN sensing and FB feedback paths |
| Output Short-Circuit Protection | Automatic hiccup-mode shutdown when ISP–ISN > 600mV - prevents damage during LED string short or wiring fault |
| C/10 Charge Termination | VMODE asserts when ISP–ISN falls below 25mV under FB regulation - provides accurate end-of-charge signal for Li-ion or supercapacitor charging |
| Low Shutdown IQ | <1µA quiescent current with EN/UVLO ≤ 0.4V - meets automotive off-mode leakage requirements |
| Robust Fault Reporting | Dedicated VMODE (open-LED), PWMOUT (overvoltage/overcurrent), and EN/UVLO hysteresis - enables system-level diagnostics without additional ICs |
Applications
| Automotive Exterior Lighting | Industrial High-Brightness LED Arrays |
|---|---|
|
Use Scenario: Driving 32V, 650mA LED strings in headlamps and fog lamps with adaptive beam control. IC Role / Device Role / Timing Role: Constant-current controller managing boost conversion while providing synchronized PWM dimming for dynamic light shaping. Use Value: Maintains ±3% current accuracy across –40°C to 125°C ambient, ensuring consistent lumen output and compliance with ECE R149 photometric standards. |
Use Scenario: Powering multi-string 48V LED fixtures in factory machine vision and UV curing systems. IC Role / Device Role / Timing Role: Configured in SEPIC mode to regulate current despite wide input variation (18–36V) from industrial SMPS supplies. Use Value: Rail-to-rail 0V–40V current sense range eliminates need for level-shifters, reducing BOM cost and layout complexity. |
| Battery & Supercapacitor Charging | Constant-Current Precision Power Supplies |
|
Use Scenario: Charging 24V LiFePO₄ battery packs or 30V supercapacitor banks from 12V vehicle systems. IC Role / Device Role / Timing Role: Constant-voltage regulator with C/10 end-of-charge detection via VMODE, combined with current limiting via ISP/ISN. Use Value: Integrated C/10 threshold (25mV) and FB overvoltage protection (VFB + 60mV) replace discrete comparators and reduce component count by ≥4. |
Use Scenario: Providing stable 0.5A–2A current-limited output for test equipment and sensor biasing. IC Role / Device Role / Timing Role: Dual-loop regulator operating in constant-current mode with analog dimming (CTRL) for fine-grained current adjustment. Use Value: ±3% current accuracy and 100kHz–1MHz frequency tuning allow optimization for low-noise lab-grade performance or compact portable designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#PBF | Requires external MOSFETs; no integrated switch; supports higher VIN (up to 100V); lacks internal PWM generator | Better suited for ultra-high-voltage LED strings (>40V) or multi-phase designs where layout control is critical | Select when >40V input or >5A output current is required; accept added BOM and layout complexity |
| LM3409QMH/NOPB | Lower max VIN (40V same), but only 1.25A switch; no integrated PWM generator; no VMODE or C/10 reporting | Targeted at lower-power (<15W) automotive interior lighting with basic ON/OFF control | Select for cost-sensitive, low-power applications where diagnostic features and wide dimming range are not required |
Compared with LTC3783EFE#PBF and LM3409QMH/NOPB, the LT3954IUHE#TRPBF uniquely combines integrated 5A switching, on-chip 3000:1 PWM dimming, and comprehensive fault reporting (VMODE, PWMOUT, C/10) in a single 5mm × 6mm QFN - reducing total solution size by ≥35% versus discrete alternatives.
Availability
LT3954IUHE#TRPBF is available at Aetrix Electronics and suitable for automotive lighting, industrial LED arrays, and battery charging applications requiring stable component supply, extended temperature operation (–40°C to 125°C), and long-term manufacturing continuity.
Supply support for LT3954IUHE#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 acquired Linear Technology in 2017 and maintains its precision analog and power management product lines with full datasheet, simulation model, and application support.
The LT3954IUHE#TRPBF belongs to Linear's high-performance LED driver family, engineered specifically for demanding constant-current applications where accuracy, reliability, and integrated diagnostics are critical - especially in automotive and industrial environments.
FAQ
What is the maximum output power achievable with the LT3954IUHE#TRPBF in boost configuration?
The LT3954IUHE#TRPBF supports up to ~20W output in boost mode (e.g., 24V input → 32V/650mA LED string), limited by its 40V/5A internal MOSFET, thermal design of the 5mm × 6mm QFN package, and typical 95% efficiency at optimal switching frequency. Higher power requires external FETs or parallel configurations - which the LT3954IUHE#TRPBF does not support natively.
How does the LT3954IUHE#TRPBF implement open-LED detection?
The LT3954IUHE#TRPBF detects open-LED conditions by monitoring two simultaneous conditions: FB voltage falling below VFB – 50mV (≈1.205V) AND ISP–ISN differential dropping below 25mV. When both occur, the open-drain VMODE pin is actively pulled low - providing a direct hardware flag usable by microcontrollers or fault loggers without software polling.
Can the LT3954IUHE#TRPBF operate in buck mode, and what are the constraints?
Yes, the LT3954IUHE#TRPBF supports buck mode using high-side current sensing (ISP connected to VIN, ISN to sense resistor top). Constraints include: VIN must exceed LED forward voltage + dropout; FB must be connected to LED cathode; and minimum on-time (180ns) limits low-duty-cycle operation at high frequencies. Full buck operation is confirmed in the datasheet's "Buck Mode" application diagram.
What is the role of the DIM/SS pin beyond soft-start in the LT3954IUHE#TRPBF?
In the LT3954IUHE#TRPBF, the DIM/SS pin serves dual functions: (1) soft-start timing via external capacitor charging, and (2) programming the internal PWM generator's duty cycle and frequency. Its internal 12µA pull-up current, combined with external current injection, sets PWMOUT's duty ratio (4%–96%) and oscillation frequency - enabling self-contained analog+PWM dimming without external controllers.
Does the LT3954IUHE#TRPBF require external compensation, and where is it applied?
Yes, the LT3954IUHE#TRPBF requires external RC compensation connected between VC and GND. This network stabilizes the current-mode control loop by setting dominant pole and phase margin. Typical values are 1nF capacitor + 100kΩ series resistor, placed directly at the VC pin per Layout Guidelines. Omitting or misplacing this network causes instability or poor transient response.
LT3954IUHE#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):
- 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#TRPBF FAQ
1.How can I place an order for LT3954IUHE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3954IUHE#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 LT3954IUHE#TRPBF reliable?
The price and inventory of LT3954IUHE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3954IUHE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3954IUHE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3954IUHE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3954IUHE#TRPBF?
LT3954IUHE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3954IUHE#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 LT3954IUHE#TRPBF?
For technical support, including LT3954IUHE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3954IUHE#TRPBF requirements.
6.How does Aetrix verify that LT3954IUHE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3954IUHE#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 LT3954IUHE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3954IUHE#TRPBF?
All LT3954IUHE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3954IUHE#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 LT3954IUHE#TRPBF part is unused and in its original packaging.
Return procedure for LT3954IUHE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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