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Analog Devices Inc. LT3477EFE#TRPBF
- Part No.:
- LT3477EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3477EFE#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3A 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,919
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Product details
Overview
LT3477EFE#TRPBF from Analog Devices (formerly Linear Technology) is a current-mode, 3A DC/DC step-up converter with dual rail-to-rail current sense amplifiers and an internal 42V NPN switch. It delivers up to 93% efficiency, supports 200kHz–3.5MHz programmable switching frequency via RT pin, and operates across 2.5V–25V input voltage range. It enables constant-current/constant-voltage operation for high-power LED drivers in boost, buck-boost, or inverting topologies.
For engineers reviewing the LT3477EFE#TRPBF datasheet, LT3477EFE#TRPBF pinout, LT3477EFE#TRPBF application, or LT3477EFE#TRPBF equivalent, this page provides verified technical context, validated pin functions, confirmed thermal and electrical specifications, and real-world implementation guidance for LED driver, distributed power, and dual-loop current-limited converter designs.
Technical Context
The LT3477EFE#TRPBF implements fixed-frequency current-mode control with independent voltage feedback (via FBP/FBN) and two dedicated current feedback loops (ISP1/ISN1 and ISP2/ISN2), each with 100mV rail-to-rail sense threshold. Its dual-loop architecture allows seamless transition between constant-voltage and constant-current regulation modes without external logic.
It features an externally compensated error amplifier (VC pin), programmable soft-start (SS pin), and dual IADJ pins enabling independent adjustment of both current sense thresholds down to <625mV - supporting dynamic current scaling for LED brightness or battery charge control without resistor changes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 25V - supports wide-input industrial and automotive supply rails without pre-regulation. |
| Switch Current Limit | 3A nominal - sustains continuous 3A output current in boost/buck-boost with internal 42V NPN switch. |
| Current Sense Threshold | 100mV per channel - enables precise, low-loss current sensing with minimal voltage drop across sense resistors. |
| Switching Frequency Range | 200kHz to 3.5MHz - set by external RT resistor; higher frequencies reduce inductor size but trade off efficiency. |
| Reference Voltage | 1.235V (E-grade) - stable bandgap reference used for output voltage setting and feedback loop accuracy. |
| Efficiency | Up to 93% - achieved in typical LED driver applications, minimizing thermal load and power loss. |
| Operating Temperature | –40°C to +85°C - specified junction temperature range for industrial-grade reliability. |
| Quiescent Current | 7.5µA (shutdown), 5mA (active) - ultra-low standby power enables always-on systems with tight power budgets. |
Pinout & Package
LT3477EFE#TRPBF is housed in a thermally enhanced 20-lead plastic TSSOP package (4.4mm × 6.5mm × 1.1mm) with exposed pad (Pin 21) soldered to PCB ground for optimal thermal performance (θJA = 40°C/W). The package includes three NC pins (18, 19, 20) and dual SW pins (16, 17) for low-inductance switch node routing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Input Power Supply | Primary input rail connection; must be locally bypassed with low-ESR ceramic capacitor. |
| RT (Pin 2) | Frequency Setting Input | Connects external resistor to GND to program switching frequency from 200kHz to 3.5MHz. |
| SHDN (Pin 3) | Shutdown Control | Active-high enable: >2V enables device; <0.3V disables switching and reduces quiescent current to 0.1µA. |
| SS (Pin 4) | Soft-Start Timing | Controls ramp rate of VC pin voltage during startup to limit inrush current and prevent output overshoot. |
| VC (Pin 5) | Error Amplifier Compensation | External RC network sets loop stability; typical values are 1kΩ + 4.7nF for robust transient response. |
| FBN (Pin 6) | Inverting Feedback Input | Connects to resistive divider tap for positive-output voltage regulation (e.g., boost mode). |
| FBP (Pin 7) | Noninverting Feedback Input | Connects to resistive divider tap for negative-output voltage regulation (e.g., inverting topology). |
| VREF (Pin 8) | Bandgap Reference Output | 1.235V reference source; supplies current to feedback dividers and can be bypassed with 100pF. |
| IADJ2 (Pin 9) | Second Current Sense Adjustment | Adjusts second current sense threshold linearly when <625mV; >650mV defaults to 100mV. |
| IADJ1 (Pin 10) | First Current Sense Adjustment | Adjusts first current sense threshold linearly when <625mV; >650mV defaults to 100mV. |
| ISP2 (Pin 11) | Second Current Sense (+) | Noninverting input of second current sense amplifier; connects to high-side of sense resistor. |
| ISN2 (Pin 12) | Second Current Sense (–) | Inverting input of second current sense amplifier; connects to low-side of sense resistor. |
| ISP1 (Pin 13) | First Current Sense (+) | Noninverting input of first current sense amplifier; used for LED string or input current sensing. |
| ISN1 (Pin 14) | First Current Sense (–) | Inverting input of first current sense amplifier; completes differential current measurement path. |
| GND (Pin 15) | Analog/Digital Ground | Common return for control circuitry; must connect directly to local ground plane. |
| SW (Pins 16, 17) | Internal Switch Collector | High-current output node connecting to inductor and diode; minimize trace area to reduce EMI. |
| NC (Pins 18, 19, 20) | No Connect | Unused pins; may be left floating, tied to GND, or connected to VIN per layout requirements. |
| PGND (Pin 21) | Power Ground / Exposed Pad | Must be soldered to PCB ground plane for thermal dissipation and low-noise power return path. |
Key Features
| Feature | Design Value |
|---|---|
| Dual rail-to-rail current sense amplifiers | Independent 100mV thresholds on ISP1/ISN1 and ISP2/ISN2 enable simultaneous input and output current limiting or multi-string LED control. |
| Programmable soft-start | SS pin controls VC ramp rate to limit peak inductor current at startup, preventing overshoot and component stress in high-current LED applications. |
| Wide input voltage range (2.5V–25V) | Eliminates need for pre-regulators in 5V, 12V, and 24V systems, simplifying power architecture for industrial and telecom equipment. |
| Capable of positive/negative output voltages | Supports boost, inverting, SEPIC, and flyback topologies via flexible FBP/FBN configuration - ideal for bipolar supply generation or isolated bias rails. |
| Thermally enhanced TSSOP package | 20-lead TSSOP with exposed PGND pad achieves θJA = 40°C/W, enabling 3A operation without heatsinking in compact layouts. |
| Low VCE(SAT) switch | 0.2V at 1A ensures minimal conduction loss and high efficiency even under heavy load conditions. |
Applications
| High-Power LED Driver | Distributed Power System |
|---|---|
|
Use Scenario: Driving 4-series white LEDs from 5V input in automotive interior lighting. IC Role / Device Role / Timing Role: Constant-current DC/DC boost controller regulating 300mA LED current with PWM dimming support up to 500:1 ratio. Use Value: Dual current sense channels allow independent monitoring of LED string current and input surge current during cold-crank events. |
Use Scenario: Generating ±12V rails from a 24V intermediate bus in telecom line cards. IC Role / Device Role / Timing Role: Inverting and boost converter core enabling bipolar output generation with single IC and shared compensation network. Use Value: Programmable 200kHz–3.5MHz switching frequency allows optimization for EMI compliance while maintaining small magnetics. |
| DSL Modem Power Supply | Input/Output Current-Limited Converter |
|
Use Scenario: Providing regulated 3.3V and –5V outputs for ADSL line driver ICs. IC Role / Device Role / Timing Role: Dual-loop regulator delivering constant-voltage output while enforcing strict input current limits during line fault conditions. Use Value: SHDN pin enables remote power cycling; low 7.5µA quiescent current meets stringent DSL standby power requirements. |
Use Scenario: Protecting downstream circuits in USB-powered test equipment with adjustable current limits. IC Role / Device Role / Timing Role: Dual current sense amplifiers independently regulate input current (ISP1/ISN1) and output current (ISP2/ISN2) for fail-safe operation. Use Value: IADJ1/IADJ2 pins allow dynamic current limit adjustment via DAC or microcontroller GPIO - no hardware change required. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3780EFE#PBF | 4-switch synchronous buck-boost controller (external MOSFETs); no integrated switch; supports 4–36V input; requires external gate drivers. | Used where higher efficiency (>95%) and bidirectional voltage conversion (VIN > VOUT or VIN < VOUT) are required; not suitable for space-constrained LED drivers. | Select LTC3780EFE#PBF when system-level efficiency and flexibility outweigh integration benefits - especially in high-volume industrial converters. |
| LT3756EFE#PBF | LED-specific boost/buck-boost controller with 100V switch; single current sense channel; optimized for analog/PWM dimming interfaces. | Targeted at high-voltage LED arrays (e.g., street lighting); lacks dual current sense capability and negative output support. | Choose LT3756EFE#PBF only for dedicated high-brightness LED applications requiring >60V output or integrated dimming logic. |
Compared with LTC3780EFE#PBF and LT3756EFE#PBF, the LT3477EFE#TRPBF offers integrated 3A/42V switching, dual independent current sensing, and native inverting topology support - making it uniquely suited for compact, dual-loop, mixed-polarity power designs where board space and functional integration are critical.
Availability
LT3477EFE#TRPBF is available at Aetrix Electronics and suitable for high-power LED driver, distributed power system, and DSL modem applications requiring stable component supply, industrial temperature operation, and long-term production continuity.
Supply support for LT3477EFE#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and medical markets.
The LT3477 belongs to Linear's high-efficiency DC/DC converter product line, designed specifically for constant-current/constant-voltage applications including LED lighting, telecom power, and precision current-limited supplies.
FAQ
What is the maximum output current capability of the LT3477EFE#TRPBF?
The LT3477EFE#TRPBF integrates a 3A, 42V NPN switch with a guaranteed 3A current limit and 0.2V VCE(SAT) at 1A. In practical boost configurations with proper thermal design and 20-lead TSSOP package, it reliably delivers continuous 3A output current - confirmed in datasheet Figure G02 and Typical Application TA01a.
Can the LT3477EFE#TRPBF generate negative output voltages?
Yes, the LT3477EFE#TRPBF supports negative output voltages using inverting topology. Per datasheet Figure F03 and Applications Information section, tie FBN to GND and use R3/R4 feedback divider on FBP to set VOUT = –1.235V × (1 + R3/R4). This capability is inherent to its dual-input error amplifier architecture.
How does the dual current sense feature work in the LT3477EFE#TRPBF?
The LT3477EFE#TRPBF contains two independent rail-to-rail current sense amplifiers: one on ISP1/ISN1 and another on ISP2/ISN2, each with 100mV default threshold. They operate simultaneously - e.g., ISP1/ISN1 can monitor LED string current while ISP2/ISN2 monitors input current - with priority-based regulation enforced by internal summing amplifier A3.
What is the purpose of the IADJ1 and IADJ2 pins on the LT3477EFE#TRPBF?
IADJ1 and IADJ2 allow linear adjustment of their respective current sense thresholds. Applying <625mV to either pin scales the 100mV sense voltage proportionally (e.g., 309mV → 50mV threshold), enabling dynamic current control for LED dimming or battery charging without changing sense resistors - as verified in datasheet Section "Selecting RSENSE/Current Sense Adjustment".
Is the LT3477EFE#TRPBF RoHS-compliant and lead-free?
Yes, the LT3477EFE#TRPBF carries the #TRPBF suffix indicating lead-free finish and RoHS compliance. Per Linear's packaging documentation, the TSSOP package uses matte tin lead finish and meets JEDEC J-STD-020 moisture sensitivity level 3, with tape-and-reel packaging for automated assembly.
LT3477EFE#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:
- Flyback, SEPIC, Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 2.5V
- Voltage - Supply (Max):
- 25V
- Voltage - Output:
- -
- Current - Output / Channel:
- 3A (Switch)
- Frequency:
- 200kHz ~ 3.5MHz
- Dimming:
- PWM
- Applications:
- -
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
LT3477EFE#TRPBF FAQ
1.How can I place an order for LT3477EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3477EFE#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 LT3477EFE#TRPBF reliable?
The price and inventory of LT3477EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3477EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3477EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3477EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3477EFE#TRPBF?
LT3477EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3477EFE#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 LT3477EFE#TRPBF?
For technical support, including LT3477EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3477EFE#TRPBF requirements.
6.How does Aetrix verify that LT3477EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3477EFE#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 LT3477EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3477EFE#TRPBF?
All LT3477EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3477EFE#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 LT3477EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3477EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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