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Analog Devices Inc. LT3478EFE-1#PBF
- Part No.:
- LT3478EFE-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3478EFE-1#PBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:823
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Product details
Overview
LT3478EFE-1#PBF from Analog Devices (formerly Linear Technology) is a 4.5A monolithic step-up DC/DC LED driver IC with integrated 60mΩ/42V NPN switch, designed for constant-current driving of high-power LED strings in boost, buck-boost, or buck topologies. It delivers up to 1050mA LED current with true-color PWM dimming (3000:1 range), operates from 2.8V to 36V input, and features programmable soft-start, open-LED protection, and thermal derating control - used in automotive TFT LCD backlights and heads-up displays.
For engineers reviewing the LT3478EFE-1#PBF datasheet, LT3478EFE-1#PBF pinout, LT3478EFE-1#PBF application, or LT3478EFE-1#PBF equivalent, key selection criteria include its 16-pin TSSOP package with exposed pad, integrated current-sense resistor (LT3478-1 variant), 200kHz–2.25MHz programmable switching frequency, and dual CTRL pins enabling both LED current programming and temperature-based current derating.
Technical Context
The LT3478EFE-1#PBF 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.
True Color PWM™ dimming is achieved by synchronizing external MOSFET gate drive with the internal oscillator while preserving VC loop integrity; this avoids color shift by maintaining constant forward current during active PWM periods. The device supports separate VS and L pins for inductor supply decoupling and inrush current monitoring, and uses OVPSET to set programmable overvoltage protection (12.3V–41V).
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) conditions. |
| Max LED Current | 1050mA - full-scale output with CTRL1 = VREF; linearly programmable from 100mA to 1050mA via CTRL1 voltage. |
| Switch Rating | 4.5A, 42V, 60mΩ - enables high-efficiency single-stage boost for multi-LED strings without external FETs. |
| Dimming Range | 3000:1 PWM - maintains constant LED chromaticity across full brightness range, critical for display backlight uniformity. |
| Switching Frequency | 200kHz to 2.25MHz - set by RT-to-ground resistor; higher frequencies reduce inductor size but increase switching losses. |
| Junction Temp Range | –40°C to 125°C - qualified for automotive under-hood and dashboard environments with thermal shutdown protection. |
| OVP Threshold | Programmable 12.3V–41V - protects against open-LED fault by clamping VOUT using OVPSET pin voltage scaling (×41). |
Pinout & Package
LT3478EFE-1#PBF is housed in a 16-lead thermally enhanced TSSOP package (FE) with exposed pad (Pin 17) that must be soldered to PCB ground plane for thermal management (θJA = 35°C/W). The exposed pad is PGND and serves as primary heat path.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (1,2) | Internal NPN switch collector | Fused pins connect to inductor/diode node; low-inductance layout required to minimize EMI and switching losses. |
| VIN (3) | Main input supply | Supplies bias and base drive for internal switch; must be locally bypassed with ≥10µF ceramic capacitor. |
| VS (4) | Inductor supply input | Separate supply path for inductor; can be shorted to VIN if single-rail system; enables independent inrush current sensing. |
| L (5) | Inductor current sense input | Internal resistor between VS and L monitors inductor current; triggers immediate shutdown at >6A peak. |
| VOUT (6) | Boost output node | Regulated output voltage; internal circuitry detects open-LED faults by monitoring VOUT vs OVPSET threshold. |
| LED (7) | LED string cathode connection | Current flows from VOUT through LED string to this pin; internal 0.1Ω sense resistor (LT3478-1) sets LED current accuracy. |
| OVPSET (8) | Overvoltage protection reference | Sets VOUT clamp level as OVP = OVPSET × 41V; 0.3V–1V input yields 12.3V–41V protection window. |
| VC (9) | Error amplifier output & compensation | Transconductance amplifier output; connects to RC network for loop stability; controls peak switch current limit. |
| VREF (10) | 1.24V bandgap reference | Stable 1.24V source (±2.2% over temp); supplies ≤100µA; used to bias CTRL1/CTRL2/OVPSET dividers. |
| SHDN (11) | Enable/UVLO control | 1.4V threshold with 10µA hysteresis; programs system UVLO using resistor divider; 0V reduces quiescent current to 3µA. |
| CTRL1 (12) | Max LED current programming | Voltage input (0.1V–1.05V) sets full-scale LED current; linear relationship enables precise analog dimming or calibration. |
| CTRL2 (13) | Temperature derating control | Accepts negative-tempco voltage to reduce LED current above breakpoint temperature-prevents thermal runaway and extends LED life. |
| PWM (14) | External PWM dimming enable | 1V threshold; drives external N-channel MOSFET in LED cathode path; preserves True Color PWM performance up to 3000:1. |
| RT (15) | Frequency setting | Resistor to ground sets oscillator frequency (200kHz–2.25MHz); 31.6kΩ yields 1.12MHz typical. |
| SS (16) | Soft-start timing | Capacitor to ground sets startup ramp time; internal 12µA charge current limits inrush; fault discharge resets latch. |
| PGND (17) | Power ground / thermal pad | Exposed copper pad; must be soldered to large PCB ground plane for thermal dissipation and noise reduction. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 0.1Ω LED current sense | Eliminates external RSENSE, reducing BOM count and PCB area while maintaining ±5% LED current accuracy over temperature. |
| True Color PWM™ dimming | Preserves LED chromaticity across 3000:1 brightness range by maintaining constant forward current during active PWM cycles. |
| Dual CTRL pin architecture | Enables simultaneous programming of max LED current (CTRL1) and temperature-dependent current derating (CTRL2) without external ICs. |
| Programmable open-LED protection | OVPSET pin allows system-specific overvoltage threshold setting (12.3V–41V), preventing damage during LED string failure. |
| Inrush current protection | Internal VS–L current monitor shuts down switch at >6A peak, protecting inductor and diode during startup or fault conditions. |
| Separate VS and L pins | Allows independent routing of inductor supply and current sensing paths, improving noise immunity and enabling flexible board layout. |
Applications
| Automotive TFT LCD Backlight | Automotive Heads-Up Display (HUD) |
|---|---|
Use Scenario: Driving 6-series white Luxeon III LEDs from 8V–16V vehicle battery for instrument cluster backlighting. IC Role / Device Role / Timing Role: Constant-current boost controller regulating 700mA LED string; provides PWM dimming synchronized to display frame rate. Use Value: Maintains consistent color point and luminance across 3000:1 dimming range, meeting automotive display contrast and viewing-angle requirements. | Use Scenario: Powering high-brightness green/cyan LED array in projection-based HUD requiring stable current under engine vibration and thermal cycling. IC Role / Device Role / Timing Role: Buck-boost LED driver delivering 350mA at 24V output from 12V nominal supply; uses CTRL2 for thermal derating above 75°C ambient. Use Value: Prevents LED degradation by reducing current above thermal breakpoint, extending lifetime beyond 10,000 hours in sealed optical enclosure. |
| Commercial Aircraft Cabin Lighting | Industrial Control Panel Backlighting |
Use Scenario: Driving parallel strings of white LEDs for aisle lighting with DALI-compatible 0–10V analog dimming interface. IC Role / Device Role / Timing Role: Boost converter operating at 1MHz (RT = 31.6kΩ) to minimize EMI in avionics-sensitive environment; SHDN pin controlled by DALI receiver. Use Value: Meets DO-160G Section 20 radiated emissions limits due to fixed-frequency operation and low-noise layout enabled by TSSOP package. | Use Scenario: Illuminating membrane keypad and status indicators in factory HMI panel exposed to 0–70°C ambient with 36V DC industrial power rail. IC Role / Device Role / Timing Role: Buck-mode LED driver (VIN = 36V, VOUT = 12V) powering 1050mA LED string; uses OVPSET = 0.3V for 12.3V overvoltage clamp. Use Value: Survives 36V transients per IEC 61000-4-4; integrated switch eliminates need for external 40V MOSFET, reducing component count and failure points. |
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 |
|---|---|---|---|
| LT3478EFE#PBF | Uses external RSENSE; supports >1A LED current and sub-100mA precision via adjustable VSENSE (10mV–105mV). | Preferred when ultra-low LED current (<200mA) or >1A output is required; requires additional 0.1Ω resistor and layout space. | Select LT3478EFE#PBF when design needs extended current range or higher accuracy at low currents; not drop-in compatible due to different sense topology. |
| LM3409QMY/NOPB | 4A buck LED driver with 0.215Ω internal switch; no integrated OVP or dual CTRL pins; requires external current sense amp for closed-loop dimming. | Better suited for lower-voltage (≤24V) buck-only applications; lacks True Color PWM and programmable thermal derating. | Choose LM3409QMY/NOPB for cost-sensitive 24V systems where 3000:1 dimming and thermal protection are not mandatory. |
Compared with LT3478EFE#PBF, the LT3478EFE-1#PBF simplifies design with integrated current sense but trades off fine current resolution below 100mA; versus LM3409QMY/NOPB, it delivers superior dimming fidelity and thermal safety at the cost of higher BOM complexity for non-automotive use cases.
Availability
LT3478EFE-1#PBF is available at Aetrix Electronics and suitable for automotive TFT LCD backlights, heads-up displays, and industrial control panel backlighting requiring stable component supply, AEC-Q200-aligned reliability, and long-term production continuity.
Supply support for LT3478EFE-1#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3478/LT3478-1 product line was designed specifically for high-reliability, high-brightness LED lighting in automotive and industrial environments where thermal robustness, wide input range, and precise current regulation are critical.
FAQ
What is the maximum LED current supported by the LT3478EFE-1#PBF?
The LT3478EFE-1#PBF supports a maximum LED current of 1050mA when CTRL1 is set to the VREF voltage (1.24V). At 700mA output, the device maintains ±3% accuracy over temperature and line variations. This full-scale current is enabled by the integrated 0.1Ω current-sense resistor, eliminating external components required by the standard LT3478 variant.
How does True Color PWM™ dimming work in the LT3478EFE-1#PBF?
True Color PWM™ dimming in the LT3478EFE-1#PBF maintains constant LED forward current during active PWM periods by preserving the VC loop regulation state while toggling the external MOSFET via the PWM pin. This prevents current droop and color shift, enabling a verified 3000:1 dimming range - far exceeding conventional PWM drivers limited to ~100:1 before chromaticity deviation occurs.
Can the LT3478EFE-1#PBF operate in buck configuration?
Yes, the LT3478EFE-1#PBF supports buck, boost, and buck-boost topologies. In buck mode, VIN connects to the LED anode, VOUT connects to the LED cathode via the LED pin, and the inductor bridges SW to ground. The internal 42V switch rating and 36V absolute max VIN allow safe operation with input voltages up to 36V while driving lower-voltage LED strings.
What thermal management is required for the LT3478EFE-1#PBF in continuous 1050mA operation?
For continuous 1050mA operation at 12V input and 24V output, the LT3478EFE-1#PBF dissipates ~1.8W. The 16-lead TSSOP package requires the exposed pad (Pin 17) to be soldered to ≥4 cm² of 2-oz copper ground plane to maintain junction temperature ≤125°C. Thermal vias (≥6×0.3mm) beneath the pad are mandatory for automotive-grade reliability.
How is open-LED protection configured on the LT3478EFE-1#PBF?
Open-LED protection on the LT3478EFE-1#PBF is configured using the OVPSET pin: applying a voltage from 0.3V to 1.0V sets the VOUT overvoltage threshold as OVP = OVPSET × 41V. For example, 0.3V on OVPSET triggers shutdown at 12.3V, protecting the output capacitor and diode during LED string open-circuit faults - a critical feature for automotive backlight safety compliance.
LT3478EFE-1#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- 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-1#PBF FAQ
1.How can I place an order for LT3478EFE-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3478EFE-1#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 LT3478EFE-1#PBF reliable?
The price and inventory of LT3478EFE-1#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3478EFE-1#PBF is usually 5 days.
3.What payment methods are accepted for LT3478EFE-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3478EFE-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3478EFE-1#PBF?
LT3478EFE-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3478EFE-1#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 LT3478EFE-1#PBF?
For technical support, including LT3478EFE-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3478EFE-1#PBF requirements.
6.How does Aetrix verify that LT3478EFE-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT3478EFE-1#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 LT3478EFE-1#PBF meets industry standards.
7.What is the process for return or replacement of LT3478EFE-1#PBF?
All LT3478EFE-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3478EFE-1#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 LT3478EFE-1#PBF part is unused and in its original packaging.
Return procedure for LT3478EFE-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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