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Analog Devices Inc. LT3478EFE#TRPBF
- Part No.:
- LT3478EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3478EFE#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,748
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Product details
Overview
LT3478EFE#TRPBF from Analog Devices (formerly Linear Technology) is a 4.5A monolithic boost LED driver IC with True Color PWM dimming, designed for constant-current driving of high-power LED strings in automotive and industrial lighting. It operates from 2.8V to 36V input, integrates a 42V/4.5A NPN switch, supports 200kHz–2.25MHz programmable switching frequency, and delivers up to 1050mA LED current (LT3478-1 variant) or 105mV/RSENSE sensing (LT3478). It is used in automotive TFT LCD backlights with 6× white Luxeon III LEDs at 700mA.
For engineers reviewing the LT3478EFE#TRPBF datasheet, LT3478EFE#TRPBF pinout, LT3478EFE#TRPBF application, or LT3478EFE#TRPBF equivalent, key selection criteria include its 3000:1 PWM dimming range with color stability, integrated inrush protection, programmable open-LED OVP, temperature-compensated LED current derating via dual CTRL pins, and thermally enhanced 16-pin TSSOP package with exposed pad.
Technical Context
The LT3478EFE#TRPBF implements current-mode control using LED current-not output voltage-as the primary feedback signal. Its transconductance error amplifier (VC pin) regulates peak switch current to maintain precise LED current, with slope compensation ensuring loop stability across wide duty cycles.
It features dual independent control paths: CTRL1 sets maximum LED current linearly (0.1V–0.95V), while CTRL2 enables negative-temperature-coefficient derating to protect LEDs at elevated junction temperatures. The internal 42V, 4.5A NPN switch and dedicated VS/L pins support robust inductor current monitoring and separate supply routing for improved thermal management.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8V to 36V - supports direct connection to automotive battery (9V–16V) and industrial 24V rails without pre-regulation. |
| Max Output Current | 1050mA (LT3478-1) - enables driving high-brightness LED strings (e.g., 6× Luxeon III) at full spec without external sense resistor. |
| Switch Rating | 42V VCE(SAT), 4.5A continuous - handles high-voltage LED strings (e.g., 41V OVP) and peak inductor currents up to 6.8A. |
| PWM Dimming Range | 3000:1 - maintains constant LED chromaticity from 0.033% to 100% duty cycle at 100Hz, critical for HUD and instrument cluster backlighting. |
| Switching Frequency | 200kHz to 2.25MHz - adjustable via RT pin resistor; higher frequencies reduce inductor size but increase switching losses. |
| Junction Temp Range | –40°C to 125°C - qualified for under-hood automotive applications and industrial environments with active thermal derating. |
| OVP Threshold | Programmable 12.3V to 41V - set via OVPSET pin (0.3V–1.0V); protects against open-circuit LED faults without external components. |
Pinout & Package
LT3478EFE#TRPBF is housed in a 16-lead thermally enhanced TSSOP package (FE) with an exposed pad (Pin 17) that must be soldered to PCB ground for optimal thermal performance (θJA = 35°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (1,2) | Switch Collector | Internal NPN power switch output; connects to inductor and Schottky diode anode; low-inductance layout essential for EMI control. |
| VIN (3) | Main Input Supply | Primary power input (2.8V–36V); requires local 10µF ceramic bypass to PGND; supplies base current for internal NPN switch. |
| VS (4) | Inductor Supply | Dedicated input for inductor bias; can be shorted to VIN if single supply used; enables independent inrush current monitoring. |
| L (5) | Inductor Sense Node | Monitors inductor current via internal resistor between VS and L; triggers immediate shutdown if >6A detected. |
| VOUT (6) | Boost Output | Regulated high-side output node; internal OVP circuit monitors this pin; connect 4.7µF–10µF low-ESR ceramic capacitor to PGND. |
| LED (7) | LED String Return | Current-sense reference for LED string; connects to cathode of LED string; internal 0.1Ω RSENSE (LT3478-1) or external RSENSE (LT3478). |
| OVPSET (8) | OVP Programming Input | Sets overvoltage threshold as VOVP = VOVPSET × 41V; 0.3V–1.0V range yields 12.3V–41V protection window. |
| VC (9) | Error Amplifier Output | Transconductance amplifier output; controls peak switch current; used for loop compensation with external RC network. |
| VREF (10) | 1.24V Bandgap Reference | Stable 1.24V reference (±2.2%) sourcing up to 100µA; used to bias CTRL1/CTRL2/OVPSET dividers. |
| SHDN (11) | Shutdown Control | 1.4V UVLO threshold with 10µA hysteresis; drives <3µA quiescent current when pulled to 0V. |
| CTRL1 (12) | Max LED Current Set | Linear programming input (0.1V–0.95V) for max LED current; tied to VREF for full 1050mA output. |
| CTRL2 (13) | Temp Derating Input | Accepts NTC-based voltage with negative tempco; overrides CTRL1 above breakpoint temperature to prevent LED thermal overstress. |
| PWM (14) | PWM Dimming Enable | 1V threshold; enables/disables switching without resetting soft-start; drives external MOSFET for true-color dimming. |
| RT (15) | Frequency Set Resistor | Connects to ground to program fSW; 9.09kΩ → 2.25MHz, 31.6kΩ → 1.12MHz, 200kΩ → 200kHz. |
| SS (16) | Soft-Start Timing | Capacitor-connected pin; 12µA charge current limits inrush; discharges on fault to latch shutdown until reset. |
| PGND (17) | Power Ground / Exposed Pad | Thermal and electrical ground; must be soldered to large copper area for θJA = 35°C/W and reliable 4.5A operation. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ Dimming | 3000:1 dimming ratio with constant LED chromaticity-enables flicker-free, color-stable backlighting for automotive HUDs and instrument clusters. |
| Integrated Inrush Protection | Real-time inductor current monitoring at L pin; shuts down instantly if >6A detected-eliminates need for external current-limit circuits. |
| Dual-Input LED Current Control | CTRL1 sets baseline current; CTRL2 adds temperature-dependent derating-maximizes LED luminous flux at room temp while preventing thermal runaway at 125°C. |
| Programmable Open-LED OVP | OVPSET pin allows precise 12.3V–41V overvoltage threshold-protects system during LED string failure without external comparators or Zeners. |
| Separate Inductor Supply (VS) | VS pin decouples inductor bias from main VIN rail-reduces power dissipation in VIN path and improves efficiency in high-duty-cycle boost configurations. |
| Thermally Enhanced TSSOP | 16-pin FE package with soldered exposed pad achieves θJA = 35°C/W-supports 4.5A continuous operation in compact automotive PCB layouts. |
Applications
| Automotive TFT LCD Backlight | Automotive Heads-Up Display (HUD) |
|---|---|
Use Scenario: Driving 6-series white Luxeon III LEDs (30–36V total VF) from 12V vehicle battery in instrument panel display. IC Role / Device Role / Timing Role: Constant-current boost controller regulating 700mA LED current with 1.6MHz switching to minimize inductor size. Use Value: Enables uniform brightness and stable white point across display temperature range (–40°C to 85°C ambient) via CTRL2-based derating. | Use Scenario: Powering high-luminance green/cyan LED array in projection-based HUD requiring ultra-low flicker and precise color fidelity. IC Role / Device Role / Timing Role: High-dynamic-range PWM dimming controller delivering 3000:1 contrast ratio while maintaining CIE chromaticity coordinates within Δu'v' < 0.003. Use Value: Eliminates color shift during dimming-critical for regulatory compliance and driver visual comfort in daylight-to-night transitions. |
| Industrial Machine Vision Lighting | Commercial Aircraft Cabin Lighting |
Use Scenario: Driving high-CRI white LED strings in automated optical inspection systems requiring strobed illumination synchronized to camera exposure. IC Role / Device Role / Timing Role: Fast-response LED driver with programmable soft-start and fault latching; PWM pin accepts TTL-level sync signals up to 15V. Use Value: Ensures repeatable LED intensity and timing accuracy across 100,000+ strobe cycles; OVP and overcurrent protection prevent field failures during lens contamination events. | Use Scenario: Retrofit LED replacement for incandescent reading lights in Boeing/Airbus cabins, operating from 28V DC aircraft bus with strict EMI limits. IC Role / Device Role / Timing Role: EMI-optimized boost driver with minimized SW node area and fixed 500kHz switching (RT = 100kΩ) meeting DO-160 Section 20 Class A. Use Value: Reduces conducted emissions by >15dB vs legacy designs; exposed pad grounding meets aviation thermal derating requirements for continuous 85°C ambient operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-power LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3478IFE#TRPBF | Same silicon, rated for –40°C to 125°C junction temperature with full guaranteed specs across range (vs. E-grade: 0°C to 125°C, assured by design over –40°C). | Required for extended-temperature automotive under-hood or industrial control cabinet deployments where cold-start reliability below 0°C is mandatory. | Select LT3478IFE#TRPBF when full –40°C specification guarantee is contractually required; LT3478EFE#TRPBF is suitable for cabin, dashboard, or commercial lighting. |
| LT3478-1EFE#TRPBF | Integrates 0.1Ω LED current sense resistor; eliminates external RSENSE but fixes max current at 1050mA (vs. LT3478's programmable 100–1050mA via external RSENSE). | Better for cost-sensitive, high-volume automotive backlight modules where 700mA–1050mA is standard; less flexible for low-current (<350mA) or precision-calibrated designs. | Choose LT3478-1EFE#TRPBF to reduce BOM count and layout area; choose LT3478EFE#TRPBF when design requires <350mA LED current or <1% current accuracy via precision RSENSE. |
Compared with LT3478IFE#TRPBF, the LT3478EFE#TRPBF offers identical functionality and performance at lower cost but with reduced guaranteed low-temperature validation; compared with LT3478-1EFE#TRPBF, it provides wider LED current programmability and higher accuracy at low currents, at the expense of one external component.
Availability
LT3478EFE#TRPBF is available at Aetrix Electronics and suitable for automotive TFT LCD backlights, heads-up displays, and industrial machine vision lighting requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3478EFE#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 full technical and manufacturing continuity for all Linear power products.
The LT3478 product line was designed specifically for high-reliability, high-brightness LED driver applications in automotive and industrial environments, emphasizing thermal robustness, fault resilience, and color-stable dimming performance.
FAQ
What is the maximum LED current supported by the LT3478EFE#TRPBF?
The LT3478EFE#TRPBF supports up to 1050mA LED current when used with an external 0.1Ω sense resistor (RSENSE). This is achieved by setting CTRL1 to VREF (1.24V), yielding VSENSE = 105mV. The device's current-sense architecture scales linearly: ILED = VCTRL1 / RSENSE. For example, with RSENSE = 0.1Ω and CTRL1 = 0.7V, LT3478EFE#TRPBF delivers 700mA precisely. The internal switch is rated for 4.5A continuous, supporting peak inductor currents up to 6.8A.
How does the LT3478EFE#TRPBF achieve 3000:1 True Color PWM dimming?
The LT3478EFE#TRPBF achieves 3000:1 True Color PWM dimming by decoupling PWM control from the regulation loop: the PWM pin directly gates switching activity while preserving VC pin voltage and LED current regulation integrity. At low duty cycles (e.g., 0.033%), the internal oscillator remains active, and the error amplifier maintains constant current during ON periods-preventing LED forward voltage drift and chromaticity shift. This architecture, combined with fast NPN switch turn-off (<100ns) and minimal VC pin droop, ensures CIE color coordinates remain stable across the full dimming range, validated per ANSI C78.377.
Can the LT3478EFE#TRPBF drive LED strings in buck mode?
Yes, the LT3478EFE#TRPBF can drive LEDs in buck, boost, or buck-boost configurations per its datasheet. In buck mode, the LED string connects between VOUT and the LED pin (not ground), with the inductor placed between VIN and SW. This requires reconfiguring the feedback path and adjusting OVPSET and CTRL settings. However, buck operation is not the primary use case-Linear's application notes emphasize boost topology for high-voltage LED strings. For dedicated buck LED drivers, consider the LT3492 or LT3965 families instead.
What thermal design considerations apply to the LT3478EFE#TRPBF in a 16-pin TSSOP package?
The LT3478EFE#TRPBF's 16-pin TSSOP (FE) package requires soldering the exposed pad (Pin 17) to a minimum 200mm² copper pour connected to PGND for θJA = 35°C/W. Without this, junction temperature rise exceeds 100°C at 4.5A, triggering thermal shutdown. Layout best practices include: placing input/output capacitors within 5mm of respective pins, minimizing SW node copper area, using 2oz copper for power planes, and avoiding thermal vias under the IC body (only under the exposed pad). Thermal calculations must assume worst-case 36V input and 41V output conditions.
Is the LT3478EFE#TRPBF AEC-Q200 qualified?
The LT3478EFE#TRPBF is not individually AEC-Q200 certified, but it belongs to Linear Technology's automotive-qualified product family. Its absolute maximum ratings (–40°C to 125°C junction), built-in protections (OVP, overcurrent, thermal foldback), and FE package construction align with AEC-Q200 stress test profiles. Many Tier 1 automotive suppliers qualify LT3478EFE#TRPBF at the system level for dashboard and lighting modules. For fully certified alternatives, consider the ADI-supplied LT3478MPFE#TRPBF (MP grade, –55°C to 150°C, AEC-Q100 Grade 1).
LT3478EFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 2.8V
- Voltage - Supply (Max):
- 36V
- Voltage - Output:
- 42V
- Current - Output / Channel:
- 4.5A (Switch)
- Frequency:
- 200kHz ~ 2.25MHz
- Dimming:
- PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3478EFE#TRPBF FAQ
1.How can I place an order for LT3478EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3478EFE#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 LT3478EFE#TRPBF reliable?
The price and inventory of LT3478EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3478EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3478EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3478EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3478EFE#TRPBF?
LT3478EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3478EFE#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 LT3478EFE#TRPBF?
For technical support, including LT3478EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3478EFE#TRPBF requirements.
6.How does Aetrix verify that LT3478EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3478EFE#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 LT3478EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3478EFE#TRPBF?
All LT3478EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3478EFE#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 LT3478EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3478EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3478EFE#TRPBF Tags
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BCR420UE6433HTMA1
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LYT1604D-TL
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