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Analog Devices Inc. LT3474IFE-1#TRPBF
- Part No.:
- LT3474IFE-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3474IFE-1#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 1A 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,500
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Product details
Overview
LT3474IFE-1#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode step-down DC/DC converter optimized as a constant-current LED driver with integrated boost diode and high-side current sensing. It delivers up to 1 A output current with ±2% LED current accuracy over 35 mA–1 A, supports 4V–36V input, and drives LED strings up to 26 V. Designed for automotive lighting and architectural backlighting, it features True Color PWM™ dimming with 400:1 range without color shift.
For engineers reviewing the LT3474IFE-1#TRPBF datasheet, LT3474IFE-1#TRPBF pinout, LT3474IFE-1#TRPBF application, or LT3474IFE-1#TRPBF equivalent, key selection criteria include its 26 V LED string voltage rating (LT3474-1 variant), thermal shutdown, frequency foldback, open-circuit protection absence (vs. LT3474), and compatibility with ceramic output capacitors and small inductors at 200 kHz–2 MHz programmable switching frequency.
Technical Context
The LT3474IFE-1#TRPBF employs current-mode PWM control with cycle-by-cycle current limiting and slope compensation, enabling fast transient response and stable operation across wide duty cycles. Its internal NPN bipolar power switch is driven via a charge-pump BOOST circuit, allowing full saturation even at low input voltages.
True Color PWM™ operates by disconnecting the VC error amplifier during PWM low periods, preserving capacitor state and ensuring linear light output vs. duty cycle. The device lacks internal open-circuit protection-unlike the LT3474-so external overvoltage clamping is required when VIN > 25 V to prevent BOOST pin overvoltage during LED open faults.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4 V to 36 V - supports unregulated wall adapters, lead-acid batteries, and distributed 5–24 V rails without external pre-regulation. |
| Max LED String Voltage | 26 V - enables driving up to 7–8 series white LEDs (3.5 V each) or RGB strings with margin. |
| Output Current Accuracy | ±2% over 35 mA–1 A - ensures consistent brightness across dimming range and temperature (–40°C to 125°C). |
| Switching Frequency Range | 200 kHz to 2 MHz - set by RT resistor; higher frequencies allow <10 μH inductors and X7R/X5R ceramic caps only. |
| LED Dimming Ratio | 400:1 via PWM - maintains chromaticity within Δu'v' < 0.003 due to true current blanking, not analog current scaling. |
| Junction Temp Range | –40°C to 125°C - rated for under-hood automotive and industrial ambient environments with thermal shutdown. |
| Package Thermal Resistance | θJA = 40°C/W, θJC = 8°C/W - exposed pad (Pin 17) must be soldered to PCB ground plane for reliable 1 A continuous operation. |
Pinout & Package
LT3474IFE-1#TRPBF uses a thermally enhanced 16-lead TSSOP package (FE) with exposed GND pad (Pin 17). Pins 1 and 16 are DNC (do not connect); all GND pins (8, 15, 17) must be tied directly to PCB ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OUT (2) | Current sense resistor input | Connects to inductor and output capacitor; senses high-side current via internal 0.1 Ω resistor. |
| LED (3) | Current sense resistor output / LED anode node | Direct connection point for LED string anode; voltage limited to 26 V max (LT3474-1 spec). |
| VIN (4) | Main power input | Bypass with ≥2.2 μF X7R ceramic; supplies internal bias and switch; absolute max 36 V. |
| SW (5) | Internal switch collector | Connects to inductor and external Schottky catch diode; peak current limited to 1.5 A at 125°C. |
| BOOST (6) | Charge-pump drive node | Generates >VIN voltage to saturate NPN switch; clamp voltage 51 V; requires external 0.1 μF ceramic cap to SW. |
| RT (9) | Oscillator timing input | Resistor to GND sets frequency: 80.6 kΩ → 500 kHz; 10 kΩ → 2 MHz; 232 kΩ → 200 kHz. |
| SHDN (10) | Enable/disable control | 2.65 V threshold; pulls <2 μA when active; doubles as accurate UVLO when used with resistor divider. |
| REF (11) | 1.25 V buffered reference output | Used to set VADJ for current programming; tie to VADJ for 1 A output; max load 250 μA. |
| VC (12) | Error amplifier output | Controls peak switch current; clamped at 1.9 V; used for loop compensation; 0.8 V threshold for switching. |
| VADJ (13) | Current programming input | Set ILED = 1 A × VADJ/1.25 V; accepts 0–1.25 V; bias current <400 nA. |
| PWM (14) | Digital dimming control | Pull low to disconnect VC and freeze current regulation state; minimal leakage (<1 μA) preserves dimming linearity. |
Key Features
| Feature | Design Value |
|---|---|
| True Color PWM™ dimming | 400:1 ratio with no perceptible LED color shift-achieved by blanking VC node instead of modulating reference. |
| Integrated boost diode | Internal Schottky connected BIAS-to-BOOST eliminates external diode, reducing BOM count and layout area. |
| High-side current sensing | Enables grounded-cathode LED configuration-simplifies thermal management and eliminates floating return paths. |
| Frequency foldback | Reduces switching frequency to 20% of nominal under overload or short-circuit, limiting peak switch current and thermal stress. |
| Thermal shutdown | Activates at 125°C junction temperature and holds until die cools by ≥15°C-prevents permanent damage during sustained overloads. |
Applications
| Automotive Headlamp Control | Architectural Accent Lighting |
|---|---|
Use Scenario: Driving high-brightness white LED arrays in vehicle headlamps with adaptive beam shaping. IC Role / Device Role / Timing Role: Constant-current source regulating 700–1000 mA through 5–6 series LEDs while rejecting battery voltage transients (6–16 V). Use Value: Maintains ±2% current accuracy across –40°C to 125°C ambient, enabling ASIL-B compliant luminance stability without recalibration. | Use Scenario: Powering RGBW LED strips in museum display cases requiring precise color rendering and smooth dimming. IC Role / Device Role / Timing Role: Independent current regulator per channel (R/G/B/W), synchronized via shared PWM signal for flicker-free 400:1 dimming. Use Value: Eliminates color shift during dimming-critical for CRI >95 applications-by preserving LED forward voltage constancy via true current blanking. |
| Industrial HMI Backlighting | UV-C LED Disinfection Module |
Use Scenario: Illuminating TFT-LCD touch panels in factory HMIs exposed to wide temperature swings and EMI noise. IC Role / Device Role / Timing Role: Low-noise, fixed-frequency step-down LED driver with ceramic-only output filtering and 500 kHz switching. Use Value: Predictable 20 mVPP output ripple (with 10 μF X7R) meets EN 61000-6-3 Class B radiated emissions limits without ferrite beads. | Use Scenario: Driving pulsed 275 nm UV-C LEDs in portable sterilization wands requiring precise dose control. IC Role / Device Role / Timing Role: High-efficiency constant-current source delivering 350–800 mA pulses at 1–10 kHz with <100 ns turn-off delay. Use Value: Fast current settling (<5 μs) and cycle-by-cycle limiting ensure repeatable UV dose per pulse, critical for FDA-compliant disinfection cycles. |
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 |
|---|---|---|---|
| LTC3783EFE#TRPBF | Higher 40 V input rating; includes analog dimming; no integrated boost diode; requires external MOSFET. | Supports >30 V LED strings and multi-string configurations; better suited for high-voltage industrial signage. | Select when >26 V LED string voltage or dual-channel independent control is required; adds complexity and BOM cost. |
| MAX20050ATPA/VY+ | Automotive AEC-Q100 Grade-1; 4.5–60 V input; integrated high-side N-channel MOSFET; 1.2 A max current. | Qualified for under-hood use; includes spread-spectrum and diagnostic reporting; no True Color PWM™. | Choose for new automotive designs requiring OEM qualification; trades dimming linearity for functional safety features. |
Compared with LTC3783EFE#TRPBF and MAX20050ATPA/VY+, the LT3474IFE-1#TRPBF offers superior dimming fidelity (400:1 true PWM) and smaller solution size (integrated boost diode, TSSOP-16), but lacks AEC-Q100 certification and has lower max LED voltage than the MAX20050.
Availability
LT3474IFE-1#TRPBF is available at Aetrix Electronics and suitable for automotive lighting, architectural backlighting, and industrial HMI applications requiring stable component supply, extended temperature operation, and high-current LED regulation.
Supply support for LT3474IFE-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, Inc. (acquired Linear Technology in 2017) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and power management ICs for precision, reliability, and efficiency-critical systems.
The LT3474/LT3474-1 product line was designed specifically for high-fidelity, thermally robust LED current regulation in space-constrained and harsh-environment applications-including automotive front lighting and architectural accent systems.
FAQ
What is the maximum LED string voltage supported by the LT3474IFE-1#TRPBF?
The LT3474IFE-1#TRPBF supports up to 26 V on the LED pin, as specified in its Absolute Maximum Ratings and confirmed in the "LT3474-1 Drives LED Strings Up to 26V" feature list. This enables driving typical white LED strings of 7–8 series devices (3.5 V VF each) with margin. Exceeding 26 V risks damage; external clamping is mandatory if open-circuit conditions could raise voltage beyond this limit.
Does the LT3474IFE-1#TRPBF include open-circuit protection like the LT3474?
No, the LT3474IFE-1#TRPBF does not include internal open-circuit protection. Unlike the LT3474 (which clamps the LED pin at 14 V), the LT3474-1 variant relies on external overvoltage protection-especially when VIN exceeds 25 V-to prevent BOOST pin overvoltage during LED open faults. Figure 2 in the datasheet shows a recommended 27 V Zener clamp circuit.
How is the switching frequency programmed on the LT3474IFE-1#TRPBF?
The switching frequency of the LT3474IFE-1#TRPBF is set by a single resistor from the RT pin (Pin 9) to GND. Using an 80.6 kΩ resistor yields 500 kHz; 10 kΩ gives 2 MHz; and 232 kΩ yields 200 kHz. The relationship is monotonic and shown in the "Oscillator Frequency vs RT" graph (Figure G09). Frequency foldback reduces it to 20% under overload.
Can the LT3474IFE-1#TRPBF drive LEDs with a grounded cathode?
Yes, the LT3474IFE-1#TRPBF supports grounded-cathode LED configurations via its high-side current sensing architecture. The LED pin (Pin 3) connects to the LED anode, while the cathode connects directly to system ground-simplifying thermal design and eliminating the need for level-shifting in multi-string layouts.
What is the operating temperature range for the LT3474IFE-1#TRPBF?
The LT3474IFE-1#TRPBF is rated for –40°C to +125°C junction temperature, with guaranteed performance across this full range. This "I" grade designation makes it suitable for under-hood automotive, industrial controls, and outdoor lighting where ambient temperatures exceed 85°C.
LT3474IFE-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)
- 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-1#TRPBF FAQ
1.How can I place an order for LT3474IFE-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3474IFE-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 LT3474IFE-1#TRPBF reliable?
The price and inventory of LT3474IFE-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 LT3474IFE-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3474IFE-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3474IFE-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3474IFE-1#TRPBF?
LT3474IFE-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3474IFE-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 LT3474IFE-1#TRPBF?
For technical support, including LT3474IFE-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3474IFE-1#TRPBF requirements.
6.How does Aetrix verify that LT3474IFE-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3474IFE-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 LT3474IFE-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3474IFE-1#TRPBF?
All LT3474IFE-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3474IFE-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 LT3474IFE-1#TRPBF part is unused and in its original packaging.
Return procedure for LT3474IFE-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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