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Analog Devices Inc. LT3478IFE#TRPBF
- Part No.:
- LT3478IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3478IFE#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,946
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Product details
Overview
LT3478IFE#TRPBF from Analog Devices (formerly Linear Technology) is a 4.5A monolithic step-up DC/DC LED driver IC with True Color PWM dimming, designed for constant-current driving of high-power LED strings in boost, buck-boost, or buck configurations. It operates from 2.8V to 36V input, delivers up to 1050mA LED current (LT3478-1 variant), integrates a 42V/4.5A NPN switch, and supports programmable switching frequency from 200kHz to 2.25MHz - used in automotive TFT LCD backlights and heads-up displays.
For engineers reviewing the LT3478IFE#TRPBF datasheet, LT3478IFE#TRPBF pinout, LT3478IFE#TRPBF application, or LT3478IFE#TRPBF equivalent, key selection criteria include its 3000:1 PWM dimming range with color fidelity, integrated inductor current sensing, programmable OVP via OVPSET pin, thermal derating capability via CTRL2, and 16-pin thermally enhanced TSSOP package with exposed pad for thermal management.
Technical Context
The LT3478IFE#TRPBF implements current-mode control using LED current-not output voltage-as the primary feedback signal, enabling precise constant-current regulation across varying forward voltages. Its transconductance error amplifier (VC pin) directly regulates peak switch current, while slope compensation ensures loop stability at high duty cycles.
True Color PWM dimming is achieved by synchronizing external MOSFET gating with internal oscillator timing, maintaining fixed LED current amplitude during on-time and zero current during off-time-preserving chromaticity across 0.033%–100% duty cycle (3000:1 range). The dual CTRL pins enable independent programming of maximum LED current (CTRL1) and temperature-dependent current derating (CTRL2).
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 (LT3478-1 variant) - enables driving high-brightness LED strings without external current-sense resistor. |
| Switch Rating | 42V VCE(SAT), 4.5A continuous - handles high-voltage LED stacks and transient overloads with 270mV saturation voltage at 4.5A. |
| PWM Dimming Range | 3000:1 (0.033%–100%) - maintains consistent LED color and spectral output across full brightness range. |
| Switching Frequency | 200kHz to 2.25MHz - adjustable via RT pin resistor; higher frequencies reduce inductor size but increase switching losses. |
| OVP Threshold | Programmable 12.3V to 41V via OVPSET pin (OVP = OVPSET × 41) - protects against open-LED fault by clamping output voltage. |
| Junction Temp Range | –40°C to +125°C - fully specified and guaranteed for automotive under-hood and display backlight environments. |
Pinout & Package
LT3478IFE#TRPBF is housed in a 16-lead thermally enhanced TSSOP package (FE) with exposed pad (Pin 17) soldered to PCB ground plane for optimal thermal dissipation (θJA = 35°C/W). The exposed pad is PGND and must be electrically and thermally connected.
| 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 (2.8V–36V); requires local ceramic bypass capacitor 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 resistor between VS and L monitors inrush current - triggers shutdown at >6A. |
| VOUT (6) | Boost Output | Regulated output node; monitored for open-LED protection; connect bulk capacitor to PGND. |
| LED (7) | LED String Return | Current-sense node for LED string; internal 0.1Ω resistor (LT3478-1) or external RSENSE (LT3478) sets current. |
| OVPSET (8) | OVP Programming | Sets output overvoltage threshold: OVP = OVPSET × 41V (range 12.3V–41V). |
| VC (9) | Error Amplifier Output | Transconductance amplifier output; controls peak switch current; used for loop compensation. |
| VREF (10) | Bandgap Reference | 1.24V ±2.2% reference; supplies up to 100µA; used to bias CTRL1/CTRL2/OVPSET dividers. |
| SHDN (11) | Shutdown Control | 1.4V UVLO threshold; 10µA hysteresis enables programmable undervoltage lockout with resistor divider. |
| CTRL1 (12) | Max LED Current Set | Voltage input (0.1V–1.05V) programs max LED current linearly; 1.05V = 1050mA (LT3478-1). |
| CTRL2 (13) | Temp Derating Control | Accepts NTC-based voltage with negative tempco to reduce LED current above breakpoint temperature. |
| PWM (14) | PWM Dimming Input | 1V threshold; drives external NMOS in LED cathode path for true-color dimming; accepts 0–15V logic. |
| RT (15) | Frequency Set | Resistor to PGND sets oscillator frequency (200kHz–2.25MHz); nominal 0.64V at pin. |
| SS (16) | Soft-Start Timing | Capacitor sets soft-start ramp time; discharges during fault; recharges at 12µA after fault clearance. |
| PGND (17) | Exposed Pad | Power ground and primary thermal path; must be soldered to large copper plane for thermal reliability. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM Dimming | 3000:1 dimming ratio with constant LED current amplitude preserves chromaticity and avoids color shift. |
| Integrated Inductor Current Sensing | Internal resistor between VS and L pins detects inrush current >6A and disables switching instantly - no external sense resistor needed. |
| Programmable Thermal Derating | CTRL2 pin accepts NTC-based voltage to linearly reduce LED current above user-defined temperature breakpoint - maximizes lumen output while protecting LEDs. |
| Separate VS and L Pins | Enables independent routing of inductor supply and current-sense path - improves noise immunity and allows flexible layout for high-current paths. |
| Accurate Programmable OVP | OVPSET pin provides 1% accurate, resistor-programmable overvoltage protection (12.3V–41V) - eliminates need for external comparator and reference. |
Applications
| Automotive TFT LCD Backlight | High-Brightness Heads-Up Display (HUD) |
|---|---|
Use Scenario: Driving 6× white Luxeon III LEDs in series from 8V–16V automotive supply for instrument cluster backlighting. IC Role / Device Role / Timing Role: Constant-current boost controller regulating 700mA LED current with 500kHz switching frequency and 3000:1 PWM dimming for ambient light adaptation. Use Value: Maintains uniform brightness and color across temperature and input voltage variation; programmable OVP prevents damage during open-circuit faults. | Use Scenario: Powering green/cyan/blue Luxeon V emitters in projection-based HUD requiring precise luminance control and thermal robustness. IC Role / Device Role / Timing Role: Buck-boost LED driver delivering 350mA at 42V output with CTRL2-based thermal derating to prevent LED degradation at 100°C ambient. Use Value: Enables full-brightness operation at low temperatures while automatically reducing current above 75°C - extends LED lifetime and avoids thermal runaway. |
| Automotive Courtesy Lighting | Industrial Panel Indicator Lighting |
Use Scenario: Driving multiple parallel LED strings in door sill and footwell lighting with smooth 0–100% dimming and fast startup. IC Role / Device Role / Timing Role: Boost-mode LED driver with soft-start (SS pin capacitor) limiting inrush current during ignition-on transition; SHDN pin enables system-level sleep mode. Use Value: Eliminates turn-on flash and contactor wear; <3µA shutdown current extends battery life in parked vehicle state. | Use Scenario: Providing stable, flicker-free illumination for HMI status indicators in industrial control panels operating from 24V DC rails. IC Role / Device Role / Timing Role: Buck-mode LED driver (VIN > Vf) with fixed 1MHz switching for compact filter design; VREF pin powers external monitoring circuitry. Use Value: Delivers ripple-free current with <±1% regulation over line/load/temp - ensures consistent indicator visibility in harsh EMI environments. |
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#TRPBF | Same functionality and pinout; rated for 0°C to 125°C junction temperature (vs –40°C to 125°C for I-grade). | Suitable for commercial/industrial ambient environments where extended low-temp operation is not required. | Select LT3478EFE#TRPBF when operating ambient stays above 0°C and cost sensitivity outweighs extended temperature qualification. |
| LT3478IFE-1#TRPBF | Identical package and pinout; integrates 0.1Ω LED current-sense resistor (vs external RSENSE in LT3478IFE#TRPBF). | Reduces BOM count and layout complexity for designs targeting ≤1050mA LED current with ±5% accuracy. | Choose LT3478IFE-1#TRPBF when maximizing integration and minimizing external components is prioritized over ultra-low-current (<100mA) precision. |
Compared with LT3478EFE#TRPBF, the LT3478IFE#TRPBF offers guaranteed operation down to –40°C for automotive cold-crank scenarios; compared with LT3478IFE-1#TRPBF, it retains external RSENSE flexibility for sub-100mA or >1050mA current programming and improved low-current accuracy.
Availability
LT3478IFE#TRPBF is available at Aetrix Electronics and suitable for automotive TFT LCD backlights, heads-up displays, and industrial panel indicator lighting requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3478IFE#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 healthcare markets.
The LT3478 family was designed specifically for high-reliability, high-power LED driver applications demanding wide input range, precise current regulation, and robust fault protection - especially in automotive lighting systems where thermal resilience and color fidelity are critical.
FAQ
What is the guaranteed operating temperature range for LT3478IFE#TRPBF?
The LT3478IFE#TRPBF is guaranteed over the full –40°C to +125°C junction temperature range, making it qualified for under-hood automotive applications and industrial environments with extreme thermal cycling. This specification is verified through production testing and statistical process control - unlike the E-grade variant (LT3478EFE#TRPBF), which is only guaranteed from 0°C to 125°C.
How does LT3478IFE#TRPBF achieve True Color PWM dimming?
The LT3478IFE#TRPBF achieves True Color PWM dimming by using the PWM pin to gate an external NMOS transistor in the LED cathode path while maintaining constant peak LED current during on-time. This preserves forward voltage and spectral output across the full 3000:1 dimming range (0.033%–100%), preventing chromaticity shift common in analog dimming methods. The internal oscillator remains active, ensuring stable timing.
Can LT3478IFE#TRPBF drive LEDs in buck configuration?
Yes, the LT3478IFE#TRPBF supports buck-mode operation when the input voltage exceeds the LED string forward voltage. In this configuration, the internal switch operates as a synchronous rectifier controller, and the external Schottky diode is replaced with a low-RDS(on) NMOS. The device maintains constant-current regulation and all protection features - including OVP, thermal derating, and soft-start - remain fully functional.
What is the purpose of the separate VS and L pins on LT3478IFE#TRPBF?
VS and L pins provide independent routing for the inductor supply and current-sense path. VS supplies bias to the internal current-sense amplifier, while L connects directly to the inductor. This separation prevents noise coupling from high di/dt inductor currents into the sensing path, improves accuracy of inrush detection (>6A), and allows layout optimization - such as connecting L directly to the inductor while routing VS from a clean local supply.
How is overvoltage protection configured on LT3478IFE#TRPBF?
Overvoltage protection on LT3478IFE#TRPBF is configured using the OVPSET pin: applying a voltage from 0.3V to 1.0V sets the output clamp level as OVP = OVPSET × 41V (e.g., 1.0V → 41V). The internal comparator monitors VOUT continuously; if exceeded, the switch disables immediately and the SS pin discharges. No external components are required - the feature is fully integrated and calibrated.
LT3478IFE#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#TRPBF FAQ
1.How can I place an order for LT3478IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3478IFE#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#TRPBF reliable?
The price and inventory of LT3478IFE#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#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3478IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3478IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3478IFE#TRPBF?
LT3478IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3478IFE#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#TRPBF?
For technical support, including LT3478IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3478IFE#TRPBF requirements.
6.How does Aetrix verify that LT3478IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3478IFE#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#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3478IFE#TRPBF?
All LT3478IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3478IFE#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#TRPBF part is unused and in its original packaging.
Return procedure for LT3478IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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