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Analog Devices Inc. LT3478IFE-1#TRPBF
- Part No.:
- LT3478IFE-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3478IFE-1#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,775
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Product details
Overview
LT3478IFE-1#TRPBF from Analog Devices (formerly Linear Technology) is a 4.5A monolithic boost LED driver IC with integrated 60mΩ/42V NPN switch, designed for constant-current driving of high-power LED strings in automotive TFT LCD backlights and heads-up displays. It supports true-color PWM dimming up to 3000:1, operates from 2.8V to 36V input, delivers up to 1050mA LED current (LT3478-1 variant), and features programmable OVP, soft-start, and temperature-based LED current derating.
For engineers reviewing the LT3478IFE-1#TRPBF datasheet, LT3478IFE-1#TRPBF pinout, LT3478IFE-1#TRPBF application, or LT3478IFE-1#TRPBF equivalent, key selection criteria include its 16-pin TSSOP thermal package, integrated current-sense resistor (eliminating external RSENSE), 200kHz–2.25MHz programmable switching frequency, and dual CTRL pins enabling both max current programming and temperature-dependent derating - critical for automotive-grade reliability and color stability.
Technical Context
The LT3478IFE-1#TRPBF implements a current-mode boost topology where LED current-not output voltage-serves as the primary feedback signal. Its transconductance error amplifier (VC pin) regulates peak switch current to maintain precise constant current across varying LED forward voltages and input conditions.
It integrates two independent control paths: CTRL1 sets maximum LED current linearly (0.1V–0.95V → 100–1050mA), while CTRL2 accepts a negative-temperature-coefficient voltage to reduce LED current above a user-defined breakpoint-enabling full utilization of LED thermal limits without overcurrent stress.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8V to 36V - supports wide automotive battery range including cold-crank (6V) and load-dump (36V) transients. |
| Max LED Current | 1050mA - fixed full-scale output enabled by internal 0.1Ω sense resistor; eliminates external RSENSE placement and tolerance errors. |
| Switch Rating | 4.5A, 42V, 60mΩ - enables high-efficiency boost operation at >15W output (e.g., 6× white Luxeon III LEDs @ 700mA). |
| PWM Dimming Range | 3000:1 - maintains constant LED chromaticity across full dimming range via synchronous gate control of external MOSFET. |
| Operating Temp Range | –40°C to +125°C - fully specified and guaranteed for automotive under-hood and display module environments. |
| Switching Frequency | 200kHz to 2.25MHz - set by RT-to-ground resistor; higher frequencies shrink inductor size but require careful EMI management. |
| OVP Threshold | Programmable 12.3V to 41V - via OVPSET pin (OVP = OVPSET × 41V); protects against open-LED fault conditions. |
Pinout & Package
Package: 16-lead thermally enhanced TSSOP with exposed pad (Pin 17 = PGND). Requires soldering of exposed pad to PCB ground plane for 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; minimize trace area to reduce EMI. |
| VIN (3) | Main Input Supply | Primary power input (2.8–36V); requires local 10µF ceramic bypass to PGND. |
| VS (4) | Inductor Supply | Dedicated supply for inductor current sensing path; can be shorted to VIN if single supply used. |
| L (5) | Inductor Connection | Connects to inductor; internal VS–L resistor enables inrush current protection; open VS disables monitoring. |
| VOUT (6) | Boost Output | Regulated output node; monitored for OVP; connect 4.7–10µF low-ESR ceramic capacitor to PGND. |
| LED (7) | LED String Return | Current-sense node; internal 0.1Ω resistor (LT3478-1) between VOUT and LED sets full-scale current. |
| OVPSET (8) | OVP Programming | Sets overvoltage threshold: OVP = OVPSET × 41V; range 0.3–1.0V → 12.3–41V OVP. |
| VC (9) | Error Amplifier Output | Transconductance amplifier output; used for loop compensation; clamp voltage limits max duty cycle. |
| VREF (10) | 1.24V Reference | Stable 1.24V bandgap reference; supplies ≤100µA; used to bias CTRL1/CTRL2/OVPSET dividers. |
| SHDN (11) | Enable/UVLO Input | 1.4V threshold; enables device when >1.4V; 10µA hysteresis enables programmable UVLO with resistor divider. |
| CTRL1 (12) | Max LED Current Set | Voltage input (0–1.05V) programs max LED current: 100–1050mA (LT3478-1); linear scaling below 0.95V. |
| CTRL2 (13) | Temp Derating Control | Accepts NTC-based voltage with negative tempco; overrides CTRL1 above user-defined temperature breakpoint. |
| PWM (14) | PWM Dimming Input | 1V threshold; enables/disables switching synchronously; drives external MOSFET gate for true-color dimming. |
| RT (15) | Freq Programming | Resistor to ground sets fSW: 9.09kΩ → 2.25MHz; 31.6kΩ → 1.12MHz; 200kΩ → 0.2MHz. |
| SS (16) | Soft-Start Timing | Capacitor to ground sets soft-start ramp time; discharges during fault to latch shutdown until reset. |
| PGND (17) | Power Ground | Exposed pad; must be soldered to large PCB copper area for thermal dissipation and noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ Dimming | 3000:1 dimming ratio with constant LED chromaticity achieved via synchronous PWM gating of external MOSFET - no color shift across brightness range. |
| Integrated LED Current Sense | On-chip 0.1Ω resistor eliminates external RSENSE, reducing BOM count, layout sensitivity, and thermal drift errors in high-current applications. |
| Dual-Control LED Current Programming | CTRL1 sets baseline max current; CTRL2 injects temperature-dependent reduction - enables full LED rated current at low T, automatic derating at high T for lifetime extension. |
| Programmable Open-LED Protection | OVP threshold set via OVPSET pin (0.3–1.0V) yields 12.3–41V clamping; prevents destructive overvoltage during LED string open-circuit faults. |
| Inrush Current Protection | Internal VS–L resistor monitors inductor current; shuts down switch immediately if >6A detected - prevents startup surge damage to inductor or diode. |
| Separate Inductor Supply (VS) | VS pin decouples inductor bias from main VIN rail, enabling optimized efficiency and reduced input ripple when using separate low-noise supply for inductor path. |
Applications
| Automotive TFT LCD Backlight | Automotive Heads-Up Display (HUD) |
|---|---|
Use Scenario: Driving 6-series white Luxeon III LEDs (≈30V total VF) from 8–16V automotive battery for instrument cluster backlighting. IC Role / Device Role / Timing Role: Constant-current boost controller regulating 700mA LED string; uses PWM pin for dashboard dimming synchronized to ambient light sensor. Use Value: Maintains consistent white point across 3000:1 dimming range while surviving load-dump transients up to 36V and operating reliably at –40°C to +105°C ambient. | Use Scenario: Powering high-brightness green/cyan LED array (≈25V VF) in projection-based HUD requiring stable luminance under engine vibration and thermal cycling. IC Role / Device Role / Timing Role: High-efficiency boost driver with temperature derating (via CTRL2) to prevent LED degradation at hood temperatures >85°C. Use Value: Enables full 1050mA drive at cold start, then automatically reduces current above 60°C using NTC network on CTRL2 - extending LED lifetime by >2× vs fixed-current designs. |
| Commercial Aircraft Cabin Lighting | Industrial Control Panel Illumination |
Use Scenario: Driving parallel strings of high-CRI white LEDs (12–24V VF) in passenger reading lights with DALI-compatible 0–10V analog dimming interface. IC Role / Device Role / Timing Role: LED current regulator accepting 0–10V control signal mapped to CTRL1; uses SHDN pin for DALI-controlled on/off sequencing. Use Value: Eliminates need for external DAC or op-amp interface; 2.8V min input ensures operation during aircraft APU brownouts; 125°C junction rating supports sealed enclosure mounting. | Use Scenario: Illuminating membrane keypad and status indicators in factory HMIs exposed to oil mist, vibration, and 0–70°C ambient swings. IC Role / Device Role / Timing Role: Robust LED driver with inrush protection and open-LED detection; OVPSET configured for 24V system compliance; SS pin tied to microcontroller for controlled startup. Use Value: Prevents field failures from inductor saturation during power-on surge; detects broken LED traces before operator interaction; TSSOP package withstands IPC-A-610 Class 3 reflow profiles. |
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 | Requires external 0.1Ω RSENSE; supports >1A LED current and higher accuracy at low currents (<100mA). | Better suited for precision low-current LED arrays or designs needing >1050mA output. | Select LT3478IFE#TRPBF when external RSENSE is acceptable and extended current range or tighter low-current tolerance is required. |
| LT3965EFE#TRPBF | 4-channel 500mA LED driver with I2C interface; 60V switch; no integrated RSENSE; supports individual channel dimming. | Targeted at multi-zone RGBW backlighting or dynamic signage requiring per-channel control and diagnostics. | Choose LT3965EFE#TRPBF for applications needing digital addressability, channel independence, or higher voltage headroom (>42V). |
Compared with LT3478IFE-1#TRPBF, the LT3478IFE#TRPBF offers greater flexibility in current programming but increases component count and layout complexity, while the LT3965EFE#TRPBF trades single-channel power density for multi-channel programmability and digital control - making LT3478IFE-1#TRPBF optimal for cost-sensitive, high-reliability single-string automotive lighting.
Availability
LT3478IFE-1#TRPBF is available at Aetrix Electronics and suitable for automotive TFT LCD backlights, heads-up displays, and industrial control panel illumination requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3478IFE-1#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving automotive, industrial, communications, and aerospace markets.
The LT3478/LT3478-1 product line was engineered specifically for high-reliability, high-brightness LED lighting in harsh environments - emphasizing thermal robustness, wide input range, and true-color dimming for automotive display systems.
FAQ
What is the maximum LED current supported by the LT3478IFE-1#TRPBF?
The LT3478IFE-1#TRPBF supports a maximum LED current of 1050mA, achieved when the CTRL1 pin is set to ≥1.05V (typically tied to VREF). This full-scale value is enabled by the internal 0.1Ω current-sense resistor, eliminating external component dependencies and ensuring tight tolerance across temperature. At 700mA, the device delivers ±3% accuracy over –40°C to +125°C junction temperature.
How does the LT3478IFE-1#TRPBF implement True Color PWM dimming?
The LT3478IFE-1#TRPBF achieves True Color PWM dimming by using its PWM pin to synchronously enable/disable the internal power switch while maintaining regulation loop stability. When PWM < 1V, switching halts and VC voltage is held constant - allowing an external N-channel MOSFET in the LED return path to gate current without disrupting LED forward voltage. This preserves chromaticity across dimming ratios up to 3000:1, verified per ANSI C78.377 for white LED color consistency.
Can the LT3478IFE-1#TRPBF operate from a 12V automotive battery during cold-crank conditions?
Yes, the LT3478IFE-1#TRPBF operates down to 2.8V input, well below typical automotive cold-crank minimums of ~6V. Its 1.4V SHDN threshold allows direct connection to VIN for micropower UVLO, and internal circuitry remains functional at 2.8V with full 1050mA capability. Quiescent current is 6.1mA at VIN = 2.8V, ensuring reliable startup even during deep battery sag.
What thermal design considerations apply to the LT3478IFE-1#TRPBF in a 16-pin TSSOP package?
The LT3478IFE-1#TRPBF's 16-lead TSSOP includes an exposed thermal pad (Pin 17 = PGND) that must be soldered to a minimum 200mm² continuous copper ground plane on the PCB. With proper layout, θJA is 35°C/W - enabling 4.5A switching at 125°C junction temperature with ≤25°C ambient rise. Thermal vias (≥6× 0.3mm) under the pad are mandatory; insufficient copper area causes premature thermal shutdown above 3.5A continuous load.
How is open-LED protection configured on the LT3478IFE-1#TRPBF?
Open-LED protection on the LT3478IFE-1#TRPBF is implemented via the OVPSET pin: applying 0.3V–1.0V sets an overvoltage clamp at 12.3V–41V (OVP = OVPSET × 41V). When VOUT exceeds this threshold - indicating an open LED string - the internal switch disables, SS pin discharges, and the part enters latched fault mode until VOUT drops below the hysteresis threshold (~5% below OVP). No external components are required beyond the OVPSET resistor divider.
LT3478IFE-1#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
LT3478IFE-1#TRPBF FAQ
1.How can I place an order for LT3478IFE-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3478IFE-1#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 LT3478IFE-1#TRPBF reliable?
The price and inventory of LT3478IFE-1#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3478IFE-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3478IFE-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3478IFE-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3478IFE-1#TRPBF?
LT3478IFE-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3478IFE-1#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 LT3478IFE-1#TRPBF?
For technical support, including LT3478IFE-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3478IFE-1#TRPBF requirements.
6.How does Aetrix verify that LT3478IFE-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3478IFE-1#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 LT3478IFE-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3478IFE-1#TRPBF?
All LT3478IFE-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3478IFE-1#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 LT3478IFE-1#TRPBF part is unused and in its original packaging.
Return procedure for LT3478IFE-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3478IFE-1#TRPBF Tags
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