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Analog Devices Inc. LT3475IFE-1#TRPBF
- Part No.:
- LT3475IFE-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3475IFE-1#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,684
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Product details
Overview
LT3475IFE-1#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. It delivers precise 1.5A output per channel over 4V–36V input, supports 3000:1 PWM dimming without color shift, and enables grounded-cathode LED operation via high-side current sensing. Designed for automotive lighting and display backlighting requiring stable current regulation.
For engineers reviewing the LT3475IFE-1#TRPBF datasheet, LT3475IFE-1#TRPBF pinout, LT3475IFE-1#TRPBF application, or LT3475IFE-1#TRPBF equivalent, key selection criteria include its 20-lead TSSOP thermal package, 600kHz default switching frequency (adjustable 200kHz–2MHz), open-LED protection (LT3475 only), and 25V max LED string voltage rating specific to the -1 variant.
Technical Context
The LT3475IFE-1#TRPBF implements a current-mode PWM architecture with dual independent control loops, each featuring internal error amplifiers (VC1/VC2), programmable oscillator (RT pin), and anti-phase switching to reduce input ripple. Its bipolar NPN switch topology requires external BOOST capacitors for gate drive above VIN.
It uses high-side current sensing through internal 0.067Ω sense resistors, enabling direct grounding of LED cathodes. The VADJ pins accept voltage-programmed current setpoints (ILED = 1.5A × VADJ/1.25V), while PWM1/PWM2 support external NFET dimming with state-hold capability for linear light control.
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. |
| Max LED String Voltage | 25V - enables driving up to ~7 white LEDs in series at typical forward voltage. | Output Current Accuracy | ±3% over 50mA–1.5A range - ensures consistent brightness across dimming and temperature. |
| Switching Frequency | 200kHz to 2MHz (RT-programmable) - allows tradeoff between inductor size and efficiency. |
| Dimming Ratio | 3000:1 true-color PWM - maintains chromaticity during deep dimming without current-based hue shift. |
| Operating Temp Range | –40°C to +125°C - qualified for under-hood automotive and industrial environments. |
| Package | 20-lead thermally enhanced TSSOP with exposed ground pad - enables >2W dissipation with proper PCB layout. |
Pinout & Package
LT3475IFE-1#TRPBF is housed in a 20-lead plastic TSSOP package with exposed thermal pad (Pin 21), requiring solder connection to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OUT1, OUT2 (Pins 1, 10) | Current sense resistor input | Connects to inductor and output capacitor; sets reference point for high-side current measurement. |
| LED1, LED2 (Pins 2, 9) | Current sense resistor output / LED anode node | Direct connection point for LED string anodes; enables grounded-cathode configuration. |
| VIN (Pins 5, 6) | Main power input | Dual pins reduce IR drop and improve thermal distribution for high-current operation. |
| SW1, SW2 (Pins 4, 7) | Internal switch collector output | Drives external inductor/diode; requires low-inductance routing to minimize EMI and switching loss. |
| BOOST1, BOOST2 (Pins 3, 8) | Charge pump drive for NPN base | Must be connected to Schottky diode + capacitor to generate >VIN gate drive voltage. |
| GND (Pins 15, 21) | Signal and power ground | Exposed pad (Pin 21) is mandatory ground connection for thermal management and noise control. |
| RT (Pin 14) | Oscillator timing input | Resistor-to-ground sets switching frequency; 24.3kΩ yields 600kHz nominal. |
| SHDN (Pin 16) | Enable/disable control | 2.6V threshold enables UVLO functionality; pull <0.3V for full shutdown (2μA quiescent). |
| REF (Pin 17) | 1.25V buffered reference output | Used to set 1.5A full-scale current when tied to VADJ; can drive external dividers. |
| VADJ1, VADJ2 (Pins 19, 12) | Current setpoint input | Voltage-programmable: ILED = 1.5A × VADJ/1.25V; supports precision analog dimming. |
| PWM1, PWM2 (Pins 20, 11) | Digital dimming control | Active-low input disconnects VC loop to hold output state; enables flicker-free 3000:1 PWM. |
| VC1, VC2 (Pins 18, 13) | Error amplifier output | Compensation node for current loop; 0.8V–1.8V clamp defines current limit range. |
Key Features
| Feature | Design Value |
|---|---|
| True-color PWM dimming | 3000:1 ratio with no perceptible LED chromaticity shift - critical for automotive interior and architectural lighting. |
| Grounded-cathode LED topology | High-side current sensing eliminates need for floating return paths - simplifies mechanical mounting and thermal design. |
| Anti-phase switching | Dual channels operate 180° out-of-phase - reduces input capacitor RMS current and EMI by canceling ripple components. |
| Frequency foldback protection | Automatically lowers switching frequency during overload or short-circuit - limits peak switch current to ≤3.2A without external circuitry. |
| Thermally enhanced TSSOP | θJC = 8°C/W with exposed pad - supports continuous 1.5A/channel operation at +125°C ambient with minimal heatsinking. |
Applications
| Automotive Headlamp Control | Architectural Accent Lighting |
|---|---|
Use Scenario: Driving dual high-brightness white LED strings in adaptive front-lighting systems (AFS) with dynamic beam shaping. IC Role / Device Role / Timing Role: Constant-current source regulating two independent 1.5A channels; anti-phase switching minimizes battery supply ripple. Use Value: Enables precise lumen matching between left/right beams and supports rapid PWM-based beam modulation without color drift. | Use Scenario: Illuminating façade features or museum displays using long-series white LED strings powered from 24V DC rails. IC Role / Device Role / Timing Role: Dual-channel step-down converter delivering regulated 1.5A to 25V LED strings; high-side sensing allows direct metal-mounting of LED modules. Use Value: Eliminates need for isolated current-sense amplifiers and supports compact, thermally efficient luminaires with >90% efficiency at 12V input. |
| Industrial Display Backlighting | Avionic Cabin Lighting |
Use Scenario: Powering edge-lit LCD backlights in ruggedized HMIs where EMI and thermal constraints limit component count. IC Role / Device Role / Timing Role: Dual synchronous buck controller with integrated switches; RT pin allows 1MHz operation to shrink inductors below 3mm height. Use Value: Reduces bill-of-materials by eliminating external MOSFETs and enables conformal coating compatibility via TSSOP footprint. | Use Scenario: Providing dimmable cabin lighting in commercial aircraft with strict DO-160 lightning surge and thermal cycling requirements. IC Role / Device Role / Timing Role: High-reliability LED driver rated for –40°C to +125°C operation; built-in UVLO and thermal shutdown meet airworthiness fault tolerance. Use Value: Qualifies for Class A avionics without derating; 25V LED voltage headroom accommodates aging-related forward voltage rise. |
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 | Capable of 2A per channel; uses external MOSFETs; supports SEPIC/Cuk topologies; no integrated current sense resistor. | Better suited for >2A or multi-topology designs; requires more external components and layout effort. | Select when higher current or topology flexibility outweighs integration and board space benefits of LT3475IFE-1#TRPBF. |
| MAX20050ATP/V+T | Single-channel 2.5A automotive-grade buck LED driver; AEC-Q100 Grade 1; integrated high-side switch; 4.5V–65V input. | Requires two units for dual-channel operation; lacks anti-phase ripple cancellation; higher input voltage range. | Select when AEC-Q100 Grade 1 certification is mandatory and dual independent channels are not required per subsystem. |
Compared with LTC3783EFE#TRPBF and MAX20050ATP/V+T, the LT3475IFE-1#TRPBF offers superior integration for dual 1.5A LED strings in space-constrained automotive and industrial lighting, with built-in current sense, true-color PWM, and thermally optimized TSSOP packaging - reducing BOM count and layout complexity without sacrificing reliability.
Availability
LT3475IFE-1#TRPBF is available at Aetrix Electronics and suitable for automotive lighting, architectural LED systems, and industrial display backlighting requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3475IFE-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 leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3475 family was designed specifically for high-current, high-efficiency LED lighting applications demanding precise current regulation, wide dimming range, and robust thermal performance in compact packages.
FAQ
What is the maximum LED string voltage supported by the LT3475IFE-1#TRPBF?
The LT3475IFE-1#TRPBF supports up to 25V on its LED1 and LED2 pins, as specified in the Absolute Maximum Ratings table. This distinguishes it from the standard LT3475 (non-1) variant, which is limited to 15V. The 25V rating enables driving longer series-connected white LED strings - typically up to seven 3.4V LEDs - making the LT3475IFE-1#TRPBF ideal for high-voltage architectural and automotive lighting applications where the LT3475IFE-1#TRPBF's extended voltage headroom is essential.
Does the LT3475IFE-1#TRPBF include open-LED protection?
No, the LT3475IFE-1#TRPBF does not include internal open-LED protection. Unlike the base LT3475, the LT3475-1 variant (including LT3475IFE-1#TRPBF) omits this feature. If the LED string opens, the LT3475IFE-1#TRPBF will attempt to regulate current by driving the output voltage toward its absolute maximum rating (25V), potentially exceeding the BOOST pin's 30V limit if VIN exceeds 25V. External overvoltage protection - such as a Zener clamp or dedicated OVP IC - is recommended when using LT3475IFE-1#TRPBF in unmonitored or safety-critical LED systems.
How is the switching frequency set on the LT3475IFE-1#TRPBF?
The switching frequency of the LT3475IFE-1#TRPBF is set using an external resistor connected from the RT pin (Pin 14) to GND. A 24.3kΩ resistor yields a nominal 600kHz frequency, and the device supports adjustment from 200kHz to 2MHz using values from 100kΩ down to 4.32kΩ, as documented in Table 1 of the datasheet. The RT pin controls a constant-frequency oscillator, and frequency selection directly impacts inductor size, efficiency, and EMI profile - allowing designers to optimize the LT3475IFE-1#TRPBF for space-constrained or low-noise applications.
Can the LT3475IFE-1#TRPBF drive LEDs with grounded cathodes?
Yes, the LT3475IFE-1#TRPBF supports grounded-cathode LED configurations via its high-side current sensing architecture. The internal 0.067Ω sense resistor is placed between the OUT pin and the LED anode, allowing the LED cathode to connect directly to system ground. This eliminates the need for level-shifting or isolated current-sense amplifiers, simplifying PCB layout, improving thermal coupling to the chassis, and enabling direct mounting of LED modules to metal heat sinks - a key advantage of the LT3475IFE-1#TRPBF in automotive and industrial lighting designs.
What is the operating temperature range of the LT3475IFE-1#TRPBF?
The LT3475IFE-1#TRPBF is rated for operation from –40°C to +125°C, corresponding to the "I" grade (industrial/automotive) temperature specification. This range is guaranteed over the full junction temperature span, with performance validated per Linear Technology Note 3. The part's thermal design - including the exposed pad (Pin 21) and low θJC of 8°C/W - enables reliable 1.5A/channel operation at maximum ambient temperature when mounted on a properly designed PCB with adequate copper area and thermal vias, making the LT3475IFE-1#TRPBF suitable for under-hood automotive and harsh-environment industrial use cases.
LT3475IFE-1#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-1#TRPBF FAQ
1.How can I place an order for LT3475IFE-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3475IFE-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 LT3475IFE-1#TRPBF reliable?
The price and inventory of LT3475IFE-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 LT3475IFE-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3475IFE-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3475IFE-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3475IFE-1#TRPBF?
LT3475IFE-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3475IFE-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 LT3475IFE-1#TRPBF?
For technical support, including LT3475IFE-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3475IFE-1#TRPBF requirements.
6.How does Aetrix verify that LT3475IFE-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3475IFE-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 LT3475IFE-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3475IFE-1#TRPBF?
All LT3475IFE-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3475IFE-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 LT3475IFE-1#TRPBF part is unused and in its original packaging.
Return procedure for LT3475IFE-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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