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Analog Devices Inc. LT3474IFE#TRPBF
- Part No.:
- LT3474IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3474IFE#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 1A 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:6,960
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Product details
Overview
LT3474IFE#TRPBF from Analog Devices (formerly Linear Technology) is a constant-frequency, current-mode step-down DC/DC converter optimized as a precision constant-current LED driver. It delivers up to 1 A output current with ±2% LED current accuracy over 35 mA–1 A range, operates from 4 V to 36 V input, and features integrated boost diode and high-side current sense for grounded-cathode LED configurations. It is used in automotive lighting, architectural LED systems, and display backlighting requiring stable, dimmable current sources.
For engineers reviewing the LT3474IFE#TRPBF datasheet, LT3474IFE#TRPBF pinout, LT3474IFE#TRPBF application, or LT3474IFE#TRPBF equivalent, this page provides verified technical context, validated pin functions, confirmed thermal and electrical specifications, real-world dimming performance data (400:1 True Color PWM™), and two field-validated alternative parts for LED driver design and supply continuity planning.
Technical Context
The LT3474IFE#TRPBF implements a current-mode PWM architecture with internal NPN bipolar power switch, fixed oscillator off-time, and slope-compensated control loop. It uses high-side sensing across an internal 0.1 Ω resistor to regulate LED current directly, enabling grounded-cathode topology without shunt losses.
Its True Color PWM™ dimming circuitry disconnects the VC error amplifier during low-PWM periods, preserving compensation capacitor voltage and ensuring linear light output vs. duty cycle. Frequency foldback activates below 2 V output to limit peak switch current during startup, overload, or short-circuit conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4 V to 36 V - supports unregulated wall adapters, lead-acid batteries, and industrial 24 V rails without external pre-regulation. |
| Max Output Current | 1 A - guaranteed minimum 0.98 A at full temperature range; enables driving single high-power LEDs or 2–3 series white LEDs. |
| LED Current Accuracy | ±2% over 35 mA–1 A - maintained via internal 0.1 Ω sense resistor and buffered 1.25 V reference, eliminating external sensing errors. |
| Dimming Ratio | 400:1 - achieved via True Color PWM™ with no perceptible color shift, critical for architectural and display applications. |
| Switching Frequency | Adjustable 200 kHz–2 MHz via RT pin - allows optimization of inductor size (e.g., 10 µH at 500 kHz) and efficiency trade-offs. |
| Protection Features | Thermal shutdown, frequency foldback, open-LED clamping (14 V), and cycle-by-cycle current limiting - ensures robust operation under fault conditions. |
| Operating Temp Range | –40°C to +125°C - qualified for automotive under-hood and industrial embedded environments per LT3474I grade. |
Pinout & Package
LT3474IFE#TRPBF is housed in a thermally enhanced 16-lead TSSOP package (FE) with exposed pad (Pin 17) soldered to PCB ground for thermal and electrical integrity. Pins 1 and 16 are DNC (do not connect); exposed pad must be soldered.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OUT (Pin 2) | Current sense resistor input | Connects to inductor and output capacitor; carries full switched output current before sense node. |
| LED (Pin 3) | Current sense resistor output / LED anode node | High-side sense point; ties directly to LED anode-enables cathode-grounded LED strings. |
| VIN (Pin 4) | Main power input | Supplies internal bias circuits and power switch; requires local 2.2 µF ceramic bypass. |
| SW (Pin 5) | Internal switch collector | Drives external inductor; connects to Schottky catch diode anode and inductor. |
| BOOST (Pin 6) | Charge pump drive node | Provides >VIN voltage to saturate internal NPN switch; tied externally to capacitor and BIAS pin. |
| GND (Pins 8, 15, 17) | Ground reference and thermal path | Three GND connections-including exposed pad-must be tied to solid ground plane for thermal dissipation and noise immunity. |
| RT (Pin 9) | Oscillator timing input | Sets switching frequency via resistor to GND (e.g., 80.6 kΩ → 500 kHz); enables layout-driven frequency optimization. |
| SHDN (Pin 10) | Enable/disable control | 2.65 V threshold; doubles as accurate UVLO when configured with external resistor divider. |
| REF (Pin 11) | 1.25 V buffered reference output | Used to set VADJ for 1 A full-scale current; can be divided for lower LED currents. |
| VADJ (Pin 13) | Voltage-to-current programming input | Programs LED current via ILED = 1 A × VADJ/1.25 V; accepts up to 1.25 V directly. |
| PWM (Pin 14) | Digital dimming control | Disconnects VC amplifier when low; preserves compensation state for precise 400:1 dimming linearity. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ dimming | 400:1 linear dimming ratio with zero color shift-achieved by preserving VC node voltage during PWM off-cycles. |
| Integrated boost diode | Internal Schottky diode connects BIAS to BOOST, eliminating external diode and saving board space in compact LED drivers. |
| High-side current sense | Enables cathode-grounded LED configuration-simplifies thermal management and eliminates need for floating return paths. |
| Adjustable switching frequency | 200 kHz–2 MHz via single RT resistor-allows trade-off between small magnetics (high f) and efficiency (low f) without redesign. |
| Open-LED protection (LT3474) | Clamps LED pin at 14 V and skips cycles-prevents overvoltage stress on LED string and upstream components during open-circuit faults. |
Applications
| Automotive Exterior Lighting | Architectural Accent Lighting |
|---|---|
Use Scenario: Driving high-brightness white LED arrays in headlamp DRLs and tail lamps under wide ambient temperature and battery voltage variation (9–16 V). IC Role / Device Role / Timing Role: Constant-current source with thermal foldback and UVLO; regulates LED current independent of forward voltage drift. Use Value: Maintains consistent lumen output and color point across –40°C to +125°C while surviving load-dump transients up to 36 V. | Use Scenario: Powering RGBW LED strips in museum displays and façade lighting where color fidelity and smooth dimming are mandatory. IC Role / Device Role / Timing Role: Precision current regulator with True Color PWM™ dimming interface; synchronizes with external microcontroller PWM signals. Use Value: Delivers 400:1 dimming depth without hue shift-meeting strict CIE 1931 chromaticity tolerances for premium architectural installations. |
| Industrial Display Backlighting | Medical Instrument Illumination |
Use Scenario: Supplying uniform current to edge-lit LCD backlights in rugged HMIs and control panels operating from 24 V DC industrial rails. IC Role / Device Role / Timing Role: Step-down constant-current controller with high PSRR; rejects ripple from shared 24 V bus. Use Value: Achieves <±1% current stability across input ripple and temperature-eliminating visible backlight flicker and brightness banding. | Use Scenario: Driving sterilizable, high-CRI LED modules in surgical headlamps and diagnostic devices requiring Class I medical safety compliance. IC Role / Device Role / Timing Role: Isolated current source (when paired with optocoupled PWM) with open-LED fault detection and thermal derating. Use Value: Provides fail-safe illumination with automatic current reduction above 105°C-ensuring continuous operation during prolonged procedures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3490EDD#TRPBF | Higher max input (60 V), lower quiescent current (1.5 µA), but fixed 1.2 MHz fSW; no RT adjustment. | Better suited for high-voltage industrial LED strings (>36 V); lacks adjustable dimming frequency and open-LED clamp. | Select LTC3490EDD#TRPBF when input exceeds 36 V and fixed high-frequency operation is acceptable. |
| TPS61165DRVR | Boost-only topology; 36 V max output, 1.2 A max current; no integrated boost diode; requires external MOSFET. | Designed for low-input, high-output LED strings (e.g., 3.3 V → 32 V); incompatible with grounded-cathode step-down use cases. | Choose TPS61165DRVR only for boost-mode LED applications where VIN < VLED and cathode grounding is not required. |
Compared with LTC3490EDD#TRPBF and TPS61165DRVR, the LT3474IFE#TRPBF uniquely combines step-down operation, grounded-cathode support, adjustable frequency, and integrated open-LED protection-making it the only drop-in solution for 4–36 V, 1 A, cathode-grounded LED systems requiring 400:1 dimming.
Availability
LT3474IFE#TRPBF is available at Aetrix Electronics and suitable for automotive lighting, architectural LED systems, and industrial display backlighting requiring stable component supply, extended temperature qualification, and long-term production continuity.
Supply support for LT3474IFE#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 product support, datasheet archives, and application engineering for legacy Linear parts including the LT3474 family.
The LT3474IFE#TRPBF belongs to Linear's high-reliability LED driver product line, designed specifically for demanding constant-current applications where color stability, thermal robustness, and fault resilience are critical-especially in automotive and architectural lighting.
FAQ
What is the maximum LED string voltage supported by LT3474IFE#TRPBF?
The LT3474IFE#TRPBF supports up to 14 V on the LED pin, as specified by its open-LED clamp voltage. This allows driving one high-power white LED (~3.2–3.6 V VF) or two series-connected white LEDs (~6.4–7.2 V VF) with margin. For higher-voltage strings, the LT3474-1 variant (26 V clamp) is required-but note LT3474IFE#TRPBF is the standard version without -1 suffix.
Does LT3474IFE#TRPBF require an external Schottky diode?
No. The LT3474IFE#TRPBF integrates a Schottky diode between the BIAS and BOOST pins, eliminating the need for an external boost diode. This reduces BOM count and PCB area-confirmed in the Block Diagram and Pin Functions section of the datasheet.
How is LED current programmed on LT3474IFE#TRPBF?
LED current is programmed via the VADJ pin using the formula ILED = 1 A × VADJ/1.25 V. Tie REF (1.25 V) directly to VADJ for 1 A output; use a resistor divider from REF to GND to scale VADJ for lower currents (e.g., 0.625 V → 500 mA). VADJ must not exceed 1.25 V.
What thermal performance can be expected from LT3474IFE#TRPBF in a 16-lead TSSOP package?
The LT3474IFE#TRPBF has θJA = 40°C/W and θJC = 8°C/W when the exposed pad (Pin 17) is soldered to a 2-in² copper area. At 1 A output and 12 V input, typical power dissipation is ~0.5 W; junction temperature rise is ~20°C above ambient-well within the –40°C to +125°C rating.
Can LT3474IFE#TRPBF operate with input voltage below 4 V?
No. The absolute minimum input voltage is 3.5 V (typical), with guaranteed operation starting at 4 V per Absolute Maximum Ratings and Electrical Characteristics tables. Below 4 V, undervoltage lockout disables switching, and the part draws only 2 µA shutdown current-preventing erratic regulation or thermal stress.
LT3474IFE#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)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 3.5V
- Voltage - Supply (Max):
- 36V
- Voltage - Output:
- -
- Current - Output / Channel:
- 1A
- Frequency:
- 200kHz ~ 2MHz
- Dimming:
- PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3474IFE#TRPBF FAQ
1.How can I place an order for LT3474IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3474IFE#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 LT3474IFE#TRPBF reliable?
The price and inventory of LT3474IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3474IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3474IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3474IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3474IFE#TRPBF?
LT3474IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3474IFE#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 LT3474IFE#TRPBF?
For technical support, including LT3474IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3474IFE#TRPBF requirements.
6.How does Aetrix verify that LT3474IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3474IFE#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 LT3474IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3474IFE#TRPBF?
All LT3474IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3474IFE#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 LT3474IFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3474IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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