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Analog Devices Inc. LT3478IFE-1#PBF
- Part No.:
- LT3478IFE-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3478IFE-1#PBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:141
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Product details
Overview
LT3478IFE-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 supports 100mA–1050mA programmable LED current (via CTRL1), true-color PWM dimming up to 3000:1, and operates from 2.8V to 36V input across –40°C to 125°C junction temperature. Used in automotive TFT LCD backlights and heads-up displays.
For engineers reviewing the LT3478IFE-1#PBF datasheet, LT3478IFE-1#PBF pinout, LT3478IFE-1#PBF application, or LT3478IFE-1#PBF equivalent, key selection criteria include its integrated current-sense resistor (LT3478-1 variant), programmable OVP via OVPSET, thermal derating capability via CTRL2, and 16-pin thermally enhanced TSSOP package with exposed pad for thermal management.
Technical Context
The LT3478IFE-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.
It features dual control inputs: CTRL1 sets maximum LED current linearly (0.1V–0.95V → 100mA–1050mA), while CTRL2 enables temperature-dependent current derating via external NTC/resistor network-critical for maintaining LED reliability at elevated ambient temperatures without manual recalibration.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Max LED Current | 1050mA (LT3478-1 variant); set by CTRL1 voltage (e.g., 1.05V = full scale), enabling direct analog programming without external sense resistor. |
| Input Voltage Range | 2.8V to 36V; supports wide automotive battery range (cold crank to load dump) without external pre-regulation. |
| Switch Rating | 42V VCE(SAT), 4.5A continuous, 6.3A peak; handles high-side boost configurations for multi-LED strings up to ~41V output. |
| PWM Dimming Range | 3000:1 (0.033%–100% duty cycle at 100Hz); preserves constant LED chromaticity across full brightness range-essential for display backlight uniformity. |
| Operating Temp Range | –40°C to +125°C junction; fully specified and guaranteed for automotive under-hood and headlamp applications. |
| Package | 16-pin thermally enhanced TSSOP with exposed pad (Pin 17 = PGND); requires soldering to PCB ground plane for θJA = 35°C/W thermal performance. |
| Switching Frequency | 200kHz to 2.25MHz (RT-pin programmable); allows optimization between inductor size (higher fSW) and efficiency (lower fSW). |
Pinout & Package
LT3478IFE-1#PBF uses a 16-lead plastic TSSOP package with exposed thermal pad (Pin 17 = PGND). The package is thermally optimized for high-power LED driver operation and requires soldering the exposed pad to a continuous PCB ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (1,2) | Internal NPN switch collector | Fused pins connect to inductor/diode node; low-inductance layout critical for EMI reduction and switching integrity. |
| VIN (3) | Main input supply | Supplies bias and base drive for internal NPN; must be locally bypassed with low-ESR capacitor to minimize noise coupling. |
| VS (4) | Inductor supply input | Separate supply path for inductor; can be shorted to VIN if single-rail system; enables independent inrush current monitoring. |
| L (5) | Inductor current sense node | Internal resistor between VS and L monitors inductor current; triggers immediate shutdown at >6A peak to prevent saturation damage. |
| VOUT (6) | Boost output voltage node | Monitored for open-LED protection; connects to output capacitor and LED anode (in boost configuration). |
| LED (7) | LED string cathode return | Current-sense reference point; internal 0.1Ω resistor (LT3478-1) eliminates need for external RSENSE and associated board area/cost. |
| OVPSET (8) | Overvoltage protection threshold | Sets VOUT clamp level as OVP = OVPSET × 41V (e.g., 1V → 41V); protects against open-circuit LED faults. |
| 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 up to 100µA; used to bias CTRL1/CTRL2/OVPSET dividers. |
| SHDN (11) | Enable/UVLO control | 1.4V threshold with 10µA hysteresis; programs system UVLO via resistor divider; 0V forces <3µA shutdown quiescent current. |
| CTRL1 (12) | Max LED current programming | Voltage input (0.1V–1.05V) directly scales full-scale LED current (100mA–1050mA); linear response simplifies analog dimming interface. |
| CTRL2 (13) | Temperature derating control | Accepts negative-temp-coefficient voltage (e.g., NTC divider); overrides CTRL1 above breakpoint temp to protect LEDs from thermal overstress. |
| PWM (14) | External PWM dimming enable | 1V threshold; enables/disables switching while preserving VC state-enabling seamless, flicker-free dimming without color shift. |
| RT (15) | Frequency setting | Resistor-to-ground sets fSW from 200kHz–2.25MHz; higher values lower frequency, reducing switching losses at high input voltages. |
| SS (16) | Soft-start timing | Capacitor-to-ground sets startup ramp time; prevents inductor inrush; discharges during fault conditions to latch shutdown until reset. |
| Exposed Pad (17) | Power ground (PGND) | Primary thermal path; must be soldered to large copper area for thermal dissipation and EMI grounding. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ Dimming | 3000:1 dimming ratio with constant LED color-achieved by preserving regulation loop integrity during PWM blanking, not just disabling switching. |
| Integrated LED Current Sense | 0.1Ω internal resistor (LT3478-1) eliminates external RSENSE, saving BOM cost, PCB space, and trace resistance errors in high-current paths. |
| Programmable Open-LED Protection | OVPSET pin allows user-defined output voltage clamp (12.3V–41V), preventing destructive overvoltage during LED string open-circuit faults. |
| Thermal Derating via CTRL2 | Enables automatic LED current reduction vs. temperature using NTC/resistor network-maximizes light output at low temps while preventing thermal runaway at high temps. |
| Inrush Current Protection | Internal monitoring of L-pin current limits peak inductor current to 6A; triggers immediate soft-start latch discharge to prevent core saturation or MOSFET stress. |
Applications
| Automotive TFT LCD Backlight | Automotive Heads-Up Display (HUD) |
|---|---|
Use Scenario: Driving 6× white Luxeon III LEDs in series from 8V–16V automotive battery for instrument cluster or center console display. IC Role / Device Role / Timing Role: Constant-current boost controller regulating LED string current at 700mA with 500kHz switching frequency and True Color PWM dimming synchronized to display frame rate. Use Value: Delivers uniform brightness and stable white point across 3000:1 dimming range-critical for readability in daylight and nighttime conditions without color shift. | Use Scenario: Powering high-brightness green/blue LED array in projection-based HUD requiring precise luminance control and thermal robustness under hood temperatures. IC Role / Device Role / Timing Role: Buck-boost LED driver with CTRL2-based thermal derating, maintaining 350mA LED current up to 85°C ambient before linear reduction to 100mA at 125°C. Use Value: Enables full-brightness operation during cold start while preventing LED degradation at sustained high under-hood temperatures-extending display lifetime beyond 10,000 hours. |
| Automotive Courtesy Lighting | Industrial Panel Indicator |
Use Scenario: Controlling multi-color (RGB) LED strips in door sills and footwells with smooth fade-in/fade-out via analog CTRL1 voltage ramping. IC Role / Device Role / Timing Role: High-efficiency boost driver operating from 12V rail, using SHDN pin for vehicle CAN bus–triggered wake/sleep and SS pin for controlled soft-start on entry. Use Value: Eliminates need for discrete current-setting resistors per channel, reduces thermal load on PCB, and ensures consistent intensity across all cabin zones regardless of battery voltage sag. | Use Scenario: Driving high-intensity amber indicator LEDs on industrial HMI panels exposed to wide ambient temperature swings (–40°C to +85°C). IC Role / Device Role / Timing Role: Buck-mode LED driver with programmable UVLO (via SHDN divider) and OVPSET-clamped output to survive 36V transients on 24V DC power rails. Use Value: Guarantees reliable indicator visibility during brownouts and surges while maintaining CE-compliant EMI performance due to fixed-frequency operation and integrated switch. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3478EFE-1#PBF | Same silicon, but rated for 0°C to 125°C junction temperature (vs. –40°C to 125°C for IFE-1); lower guaranteed cold-start performance. | Suitable for non-automotive industrial or commercial lighting where ambient never drops below 0°C. | Select LT3478IFE-1#PBF for automotive, outdoor, or extended-temperature applications requiring full –40°C operation. |
| LT3965EFE#PBF | 4-channel 500mA LED driver with I²C interface, 60V switch, and independent PWM per channel-no integrated current sense resistor. | Better suited for RGB or multi-zone dimming systems requiring digital control and channel isolation. | Choose LT3965EFE#PBF when digital addressability, channel independence, or higher output voltage (>42V) is required; not a drop-in replacement. |
Compared with LT3478EFE-1#PBF, the LT3478IFE-1#PBF guarantees operation down to –40°C-critical for automotive cold-crank scenarios-while LT3965EFE#PBF trades single-channel 1050mA capability for four independently controllable 500mA channels and digital configurability, increasing system flexibility at the cost of analog simplicity and BOM count.
Availability
LT3478IFE-1#PBF is available at Aetrix Electronics and suitable for automotive TFT LCD backlights, heads-up displays, and industrial panel indicators requiring stable component supply, extended temperature operation, and high-reliability LED current regulation.
Supply support for LT3478IFE-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, serving automotive, industrial, communications, and healthcare markets.
The LT3478/LT3478-1 product line was designed specifically for high-power, thermally demanding LED lighting applications-including automotive front-end and cabin lighting-where precision current regulation, wide dimming range, and robust fault protection are mandatory.
FAQ
What is the maximum LED current supported by the LT3478IFE-1#PBF?
The LT3478IFE-1#PBF supports a maximum LED current of 1050mA, programmable via the CTRL1 pin voltage (e.g., 1.05V = full scale). This is enabled by its integrated 0.1Ω current-sense resistor-eliminating external components and ensuring accuracy across temperature. At 700mA, the LT3478IFE-1#PBF delivers 15W to six white Luxeon III LEDs with >90% efficiency at 12V input.
How does the LT3478IFE-1#PBF achieve True Color PWM dimming?
The LT3478IFE-1#PBF achieves True Color PWM dimming by maintaining regulation loop integrity during PWM blanking-keeping the VC pin voltage stable so LED current resumes instantly at full accuracy when PWM re-enables switching. This avoids color shift seen in simpler on/off dimming schemes. The LT3478IFE-1#PBF supports up to 3000:1 dimming range (0.033%–100% duty cycle at 100Hz) while preserving chromaticity.
Can the LT3478IFE-1#PBF operate in buck topology?
Yes, the LT3478IFE-1#PBF supports buck, boost, and buck-boost topologies. In buck mode, the LED string connects between VOUT and ground, with the inductor placed between VIN and SW. The internal 42V, 4.5A NPN switch and wide 2.8V–36V input range make it suitable for high-current buck applications such as 24V industrial LED arrays. External diode and inductor selection must comply with buck-converter requirements.
What thermal management is required for the LT3478IFE-1#PBF in high-power operation?
The LT3478IFE-1#PBF requires soldering its exposed thermal pad (Pin 17) to a continuous PCB ground plane to achieve θJA = 35°C/W. For 1050mA LED current at 12V input, typical power dissipation is ~1.2W; without proper thermal relief, junction temperature can exceed 125°C. A minimum 250mm² copper pour under the device is recommended, with thermal vias to inner/ground layers to sustain operation at full load across –40°C to 125°C.
How is overvoltage protection configured on the LT3478IFE-1#PBF?
Overvoltage protection on the LT3478IFE-1#PBF is configured via the OVPSET pin: OVP = OVPSET × 41V. Applying 0.3V to OVPSET sets a 12.3V clamp; 1.0V sets 41V-ideal for protecting against open-LED faults in 6-LED white strings (~21V forward) or 12-LED strings (~42V forward). The OVP circuit latches off switching and discharges the SS pin until fault clearance, providing robust, self-contained protection without external comparators.
LT3478IFE-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
LT3478IFE-1#PBF FAQ
1.How can I place an order for LT3478IFE-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3478IFE-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 LT3478IFE-1#PBF reliable?
The price and inventory of LT3478IFE-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 LT3478IFE-1#PBF is usually 5 days.
3.What payment methods are accepted for LT3478IFE-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3478IFE-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3478IFE-1#PBF?
LT3478IFE-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3478IFE-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 LT3478IFE-1#PBF?
For technical support, including LT3478IFE-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3478IFE-1#PBF requirements.
6.How does Aetrix verify that LT3478IFE-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT3478IFE-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 LT3478IFE-1#PBF meets industry standards.
7.What is the process for return or replacement of LT3478IFE-1#PBF?
All LT3478IFE-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3478IFE-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 LT3478IFE-1#PBF part is unused and in its original packaging.
Return procedure for LT3478IFE-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3478IFE-1#PBF Tags
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