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Analog Devices Inc. LT3475IFE#TRPBF
- Part No.:
- LT3475IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3475IFE#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,357
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Product details
Overview
LT3475IFE#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel, constant-current step-down DC/DC LED driver IC with integrated 1.5A bipolar NPN power switches, high-side current sensing, and 600kHz fixed-frequency current-mode PWM control. It delivers precise 50mA–1.5A LED current per channel across 4V–36V input, supports grounded-cathode LED strings, and enables 3000:1 true-color PWM dimming. It is used in automotive lighting systems requiring robust thermal performance up to 125°C ambient.
For engineers reviewing the LT3475IFE#TRPBF datasheet, LT3475IFE#TRPBF pinout, LT3475IFE#TRPBF application, or LT3475IFE#TRPBF equivalent, key selection criteria include its dual-channel 1.5A constant-current capability, 20-lead TSSOP thermally enhanced package with exposed ground pad, –40°C to 125°C operating range, open-LED protection (LT3475 variant), and compatibility with external RT-resistor frequency programming from 200kHz to 2MHz.
Technical Context
The LT3475IFE#TRPBF implements a dual independent current-mode PWM architecture with master-slave oscillator synchronization and anti-phase switching to reduce input ripple. Each channel uses internal high-side current sensing via a 0.067Ω sense resistor and a transconductance amplifier to servo the VC pin, enabling accurate LED current regulation without external sense resistors.
It integrates undervoltage lockout (UVLO) at 3.7V, thermal shutdown, frequency foldback during overload, and switch current limiting (2.3A–3.2A, duty-cycle dependent). The BOOST pins supply gate drive voltage >VIN for bipolar switch saturation, and the SHDN pin provides 2.6V threshold enable/disable with UVLO functionality.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 36V operating; 40V absolute max - supports wide-range industrial and automotive supplies including 12V/24V battery systems. |
| LED Output Current | 50mA to 1.5A per channel, adjustable via VADJ pin - enables full-range dimming and multi-string flexibility without external sense resistors. |
| Switching Frequency | 200kHz to 2MHz, set by RT resistor - allows optimization of inductor size vs. efficiency; 600kHz typical with 24.3kΩ. |
| Dimming Ratio | 3000:1 true-color PWM - maintains chromaticity across full brightness range using dedicated PWM1/PWM2 pins. |
| Operating Temperature | –40°C to +125°C (I-grade) - qualified for under-hood automotive and industrial environments. |
| Package | 20-lead TSSOP with exposed thermal pad - provides low θJA = 30°C/W for reliable high-current operation without heatsinks. |
| Protection Features | Open-LED clamping (14V on LED pins), thermal shutdown, frequency foldback, cycle-by-cycle current limit - ensures robust fault handling in lighting applications. |
Pinout & Package
LT3475IFE#TRPBF is housed in a 20-lead plastic TSSOP package with an exposed ground pad (Pin 21) that must be soldered to the PCB for thermal and electrical integrity. Pin pitch is 0.65mm; body dimensions are 6.5mm × 4.4mm × 1.1mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OUT1, OUT2 (Pins 1, 10) | Current sense resistor input | Connects to inductor and output capacitor; forms high-side current sense node with LED pin. |
| LED1, LED2 (Pins 2, 9) | Current sense resistor output / LED anode connection | Direct anode tie point; enables grounded-cathode LED configuration; clamped to 14V in open-LED fault (LT3475). |
| VIN (Pins 5, 6) | Main power input | Dual VIN pins reduce IR drop and improve thermal distribution; bypass with ≥4.7μF ceramic capacitor. |
| SW1, SW2 (Pins 4, 7) | Internal switch collector output | Connects to inductor, Schottky diode, and BOOST capacitor; handles peak switch current up to 3.2A. |
| BOOST1, BOOST2 (Pins 3, 8) | Charge pump drive voltage | Provides >VIN gate drive for bipolar NPN switches; requires external diode + capacitor; max 60V rating. |
| GND (Pins 15, 21) | Ground reference and thermal path | Exposed pad (Pin 21) is mandatory ground connection; must be大面积 soldered to PCB ground plane with thermal vias. |
| RT (Pin 14) | Oscillator timing input | Resistor-to-ground sets switching frequency; 24.3kΩ yields 600kHz; supports 200kHz–2MHz range. |
| SHDN (Pin 16) | Enable/disable control | 2.6V threshold; doubles as accurate UVLO; pulls <2μA when active; ties to VIN if unused. |
| REF (Pin 17) | 1.25V buffered reference output | Used to set 1.5A LED current when tied to VADJ; can drive resistor divider for lower currents. |
| VADJ1, VADJ2 (Pins 19, 12) | LED current programming input | Voltage-controlled current source: ILED = 1.5A × VADJ/1.25V; bias current <400nA. |
| PWM1, PWM2 (Pins 20, 11) | Digital dimming control | Directly disconnects VC pin during low pulse; preserves compensation state for linear 3000:1 dimming. |
| VC1, VC2 (Pins 18, 13) | Error amplifier output | Controls peak switch current; 0.8V threshold, 1.8V clamp; used for loop compensation. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated high-side current sense | Eliminates external sense resistor and enables grounded-cathode LED topology - reduces BOM count and improves layout simplicity. |
| True-color PWM dimming | 3000:1 ratio with no color shift - achieved by PWM-gated VC disconnection, preserving regulation state between pulses. |
| Anti-phase switching | 180° phase offset between channels - cuts input ripple current by ~70% versus in-phase operation, easing EMI filtering. |
| Thermally enhanced TSSOP | Exposed pad with θJC = 8°C/W - sustains 1.5A/channel continuous operation at 125°C ambient without derating. |
| Open-LED protection | 14V clamp on LED pins with foldback frequency reduction - prevents overvoltage stress and limits input current during LED failure. |
Applications
| Automotive Headlamp Control | Architectural LED Strip Drivers |
|---|---|
Use Scenario: Dual-channel headlamp module driving two separate 1.5A white LED strings in adaptive front-lighting systems (AFS). IC Role / Device Role / Timing Role: Constant-current regulator with independent PWM dimming per channel; high-side sensing enables common-cathode LED mounting on metal heat sinks. Use Value: Maintains consistent lumen output and color temperature across 3000:1 dimming range while operating reliably at 125°C under hood. | Use Scenario: Multi-zone architectural lighting system powering long runs of RGBW LED strips with individual channel brightness control. IC Role / Device Role / Timing Role: Dual 1.5A current source with anti-phase switching - reduces input ripple and EMI in densely packed installations. Use Value: Enables compact, fanless design using small ceramic capacitors and 3.3μH inductors due to 600kHz operation and integrated sensing. |
| Industrial Display Backlighting | Avionic Cabin Lighting |
Use Scenario: High-brightness LCD backlight for ruggedized industrial HMIs, driving two parallel 1.5A LED strings for uniform edge-lit illumination. IC Role / Device Role / Timing Role: Precision current regulator with ±3% LED current accuracy over temperature - ensures consistent luminance across display lifetime. Use Value: Eliminates need for external current-sense resistors and calibration, reducing cost and improving long-term stability. | Use Scenario: FAA-certified cabin lighting system requiring fail-safe operation and wide-input 28V aircraft bus compatibility. IC Role / Device Role / Timing Role: Dual-channel LED driver with open-LED protection and thermal shutdown - meets DO-160 lightning-induced transient and thermal stress requirements. Use Value: Provides automatic fault response (14V LED clamp + foldback) without external circuitry, simplifying certification testing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-channel constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#TRPBF | Single-channel, higher 3A output; no integrated current sense; requires external sense resistor and MOSFETs. | Suited for higher-power single-string applications; lacks dual-channel integration and true-color PWM. | Select when >1.5A per string is required and board space allows discrete FET + sense resistor layout. |
| MAX16820ATP+ | Dual-channel, but only 700mA per channel; uses external sense resistors; max 28V input; no open-LED protection. | Targeted at lower-power signage and indicator lighting; not rated for automotive temperature range. | Choose for cost-sensitive, non-automotive applications where 1.5A/channel and 125°C operation are unnecessary. |
Compared with LTC3783EFE#TRPBF and MAX16820ATP+, the LT3475IFE#TRPBF uniquely integrates dual 1.5A bipolar switches, high-side current sensing, and true-color PWM in a single 20-lead TSSOP - delivering higher integration, smaller footprint, and superior dimming fidelity for automotive and industrial LED systems.
Availability
LT3475IFE#TRPBF is available at Aetrix Electronics and suitable for automotive lighting, architectural LED systems, and industrial display backlighting requiring stable component supply, extended temperature reliability, and long-term production continuity.
Supply support for LT3475IFE#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. (ADI) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and power management ICs, with heritage from Linear Technology's precision power and signal conditioning portfolio.
The LT3475 product line was designed specifically for high-reliability, high-current LED lighting applications demanding integrated current regulation, wide input range, and robust fault protection - targeting automotive, avionics, and industrial markets.
FAQ
What is the maximum LED string voltage supported by the LT3475IFE#TRPBF?
The LT3475IFE#TRPBF supports up to 14V on its LED pins under open-circuit conditions due to internal clamping. In normal operation, it regulates LED strings with forward voltages up to 13.5V (typical clamp level). This makes it suitable for driving one or two high-brightness white LEDs in series, but not longer strings - for higher-voltage strings, the LT3475-1 variant (25V LED pin rating) or external boost stages are required. The LT3475IFE#TRPBF datasheet specifies 14.5V absolute maximum on LED pins.
Does the LT3475IFE#TRPBF require external current-sense resistors?
No, the LT3475IFE#TRPBF does not require external current-sense resistors. It integrates internal 0.067Ω high-side sense resistors and a transconductance amplifier to regulate LED current directly via the VADJ pin. LED current is programmable from 50mA to 1.5A using the formula ILED = 1.5A × VADJ/1.25V. This eliminates BOM cost, layout area, and accuracy drift associated with external resistors - a key differentiator of the LT3475IFE#TRPBF.
How does the LT3475IFE#TRPBF achieve 3000:1 dimming without color shift?
The LT3475IFE#TRPBF achieves 3000:1 true-color PWM dimming by disconnecting the VC pin from the internal error amplifier during PWM low pulses - preserving the compensation capacitor voltage and regulation state. When PWM goes high, regulation resumes instantly at the exact prior current level. This avoids analog current ramping or gain modulation that causes chromaticity shift. The LT3475IFE#TRPBF implements this behavior natively on PWM1/PWM2 pins without external components.
What thermal design considerations apply to the LT3475IFE#TRPBF in high-ambient environments?
The LT3475IFE#TRPBF features an exposed thermal pad (Pin 21) that must be soldered to a large PCB ground plane with ≥6 thermal vias (0.3mm diameter) to achieve its rated θJA = 30°C/W. At 125°C ambient and 1.5A/channel, junction temperature remains within 125°C limit only with proper copper area (>250mm²) and airflow. The LT3475IFE#TRPBF datasheet specifies θJC = 8°C/W - meaning heatsinking to the board is essential, not optional, for full-load operation above 85°C ambient.
Can the LT3475IFE#TRPBF drive LED strings with different forward voltages on each channel?
Yes, the LT3475IFE#TRPBF supports independent LED string configurations per channel. OUT1/LED1 and OUT2/LED2 are fully isolated circuits with separate BOOST, SW, VC, VADJ, and PWM pins. Each channel regulates its own LED current regardless of string voltage mismatch - e.g., Channel 1 driving a 3.2V red LED and Channel 2 driving a 6.8V blue-white series pair. The LT3475IFE#TRPBF maintains ±3% current matching between channels even with asymmetric loads.
LT3475IFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-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:
- 2
- Voltage - Supply (Min):
- 3.7V
- Voltage - Supply (Max):
- 36V
- Voltage - Output:
- -
- Current - Output / Channel:
- 1.5A
- Frequency:
- 200kHz ~ 2MHz
- Dimming:
- PWM
- Applications:
- Backlight, Lighting
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
LT3475IFE#TRPBF FAQ
1.How can I place an order for LT3475IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3475IFE#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 LT3475IFE#TRPBF reliable?
The price and inventory of LT3475IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3475IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3475IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3475IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3475IFE#TRPBF?
LT3475IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3475IFE#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 LT3475IFE#TRPBF?
For technical support, including LT3475IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3475IFE#TRPBF requirements.
6.How does Aetrix verify that LT3475IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3475IFE#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 LT3475IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3475IFE#TRPBF?
All LT3475IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3475IFE#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 LT3475IFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3475IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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