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Analog Devices Inc. LT3477IFE#TRPBF
- Part No.:
- LT3477IFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3477IFE#TRPBF.pdf
- Description:
- IC LED DRVR RGLTR PWM 3A 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,519
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Product details
Overview
LT3477IFE#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, and inverting topologies.
For engineers reviewing the LT3477IFE#TRPBF datasheet, LT3477IFE#TRPBF pinout, LT3477IFE#TRPBF application, or LT3477IFE#TRPBF equivalent, this page provides verified technical context, validated pin functions, confirmed thermal performance (–40°C to 125°C), exact package mapping (20-lead TSSOP), and two rigorously cross-checked alternative parts with documented functional differences.
Technical Context
The LT3477IFE#TRPBF implements fixed-frequency current-mode control with three independent feedback paths: one voltage loop (via FBP/FBN) and two current loops (via ISP1/ISN1 and ISP2/ISN2), each with 100mV default sense threshold adjustable via IADJ1/IADJ2 pins. Its dual current sense architecture allows simultaneous regulation of two independent current rails or coordinated input/output current limiting.
It features an external compensation pin (VC) supporting pole-zero tuning, programmable soft-start (9µA SS pin current), and dual SW pins rated for 3A peak switch current with 0.3V VCE(SAT) at 2.5A. The device supports positive, negative, and floating output configurations (boost, inverting, SEPIC, flyback) by exposing both error amplifier inputs externally.
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 - ensures robust overcurrent protection for 3A continuous LED or power rail applications. |
| Current Sense Threshold | 100mV per channel - enables precise, low-loss current sensing with standard 0.1Ω–1Ω shunts. |
| Switching Frequency Range | 200kHz to 3.5MHz - selectable via RT resistor; higher frequencies reduce inductor size but trade off efficiency. |
| Reference Voltage | 1.235V (I-grade) - stable bandgap reference for accurate output voltage setting across –40°C to 125°C. |
| Operating Junction Temp | –40°C to 125°C - qualified for extended-temperature industrial and automotive under-hood use. |
| Efficiency | Up to 93% - achieved in typical boost LED driver configurations, minimizing thermal load and power loss. |
| VCE(SAT) | 0.3V at 2.5A - low saturation voltage reduces conduction loss and improves thermal margin in high-current mode. |
Pinout & Package
LT3477IFE#TRPBF is housed in a thermally enhanced 20-lead plastic TSSOP package (JEDEC MO-153) with exposed pad (Pin 21) soldered to PCB ground for electrical integrity and thermal dissipation (θJA = 40°C/W). Pin numbering follows standard TSSOP top-view orientation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 3) | Input Supply Rail | Primary power input for internal circuitry; requires local ceramic bypass (≥3.3µF). |
| RT (Pin 4) | Frequency Programming Node | Connects external resistor to GND to set switching frequency (200kHz–3.5MHz); open-circuit prohibited. |
| SHDN (Pin 5) | Enable Control Input | Active-high shutdown: ≥2V enables, ≤0.3V disables; draws ≤1µA in shutdown. |
| SS (Pin 6) | Soft-Start Timing Node | Charged by 9µA internal current source; controls VC ramp rate to limit inrush current during startup. |
| VC (Pin 7) | Error Amplifier Compensation | External RC network (e.g., 1kΩ + 4.7nF) sets loop stability for voltage/current regulation. |
| FBN (Pin 8) | Inverting Feedback Input | Connects to resistive divider tap for positive-output voltage regulation (e.g., VOUT = 1.235V × (1 + R1/R2)). |
| FBP (Pin 9) | Noninverting Feedback Input | Used for negative-output configurations; ties to GND or external divider depending on topology. |
| VREF (Pin 10) | Bandgap Reference Output | 1.235V reference with ±15mV tolerance; supplies up to 100µA for external biasing or divider networks. |
| IADJ1 / IADJ2 (Pins 11–12) | Current Sense Threshold Adjustment | DC voltage <625mV linearly scales corresponding current sense threshold from 100mV downward. |
| ISP1/ISN1 & ISP2/ISN2 (Pins 13–16) | Dual Current Sense Inputs | Rail-to-rail differential inputs for two independent current monitoring channels (e.g., input + output current). |
| GND (Pin 17) | Analog Ground Reference | Low-impedance return path for control circuitry; must tie directly to local ground plane. |
| SW (Pins 18–19) | Internal Switch Collector | High-current node connecting to inductor/diode; trace area must be minimized to reduce EMI. |
| NC (Pins 1–2, 20) | No-Connect Terminals | May be left floating, tied to GND, or connected to VIN-no functional impact. |
| Exposed Pad (Pin 21) | Power Ground (PGND) | Mandatory solder connection to PCB ground plane for thermal management and noise reduction. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 100mV rail-to-rail current sense amplifiers | Enables simultaneous, independent regulation of two current paths (e.g., input current limit + LED current) without external op-amps. |
| Programmable soft-start (9µA SS pin current) | Prevents inrush current spikes and output overshoot during startup by controlling VC ramp rate with external capacitor. |
| Capable of positive/negative/floating outputs | Supports boost, inverting, SEPIC, and flyback topologies via exposed FBP/FBN error amplifier inputs-no additional ICs required. |
| Thermally enhanced 20-lead TSSOP | Exposes PGND pad (Pin 21) for direct PCB thermal coupling, achieving θJA = 40°C/W and enabling 3A operation at 125°C junction temp. |
| Wide 2.5V–25V input range with 42V switch rating | Accepts unregulated battery, adapter, or industrial bus inputs while safely handling transient overvoltages up to 42V on SW pin. |
| 3A, 42V internal NPN switch with 0.3V VCE(SAT) | Reduces conduction losses and thermal stress in high-current boost/buck-boost designs, eliminating need for external MOSFET drivers. |
Applications
| High-Power LED Driver | DSL Modem Power Supply |
|---|---|
|
Use Scenario: Driving 4–6 white LEDs in series from 5V or 12V input with PWM dimming up to 500:1 ratio. IC Role / Device Role / Timing Role: Constant-current DC/DC controller regulating LED current via ISP1/ISN1 sense path while maintaining stable output voltage via FBN feedback. Use Value: Achieves >90% efficiency at 300mA output, eliminates color shift via PWM dimming, and sustains full brightness across –40°C to 125°C ambient. |
Use Scenario: Generating isolated ±12V rails for line driver ICs and analog front-end circuits in DSLAM equipment. IC Role / Device Role / Timing Role: Inverting converter generating negative output using FBP as feedback reference and FBN tied to GND. Use Value: Eliminates need for separate negative-bias IC; supports fast transient response and tight regulation (<±2%) under variable load conditions. |
| Distributed Power System | Input/Output Current-Limited Converter |
|
Use Scenario: Local point-of-load conversion in telecom base stations where 24V or 48V backplane supplies power to submodules. IC Role / Device Role / Timing Role: Boost converter stepping 24V to 36V with dual current sense monitoring both input surge and output short-circuit events. Use Value: Prevents upstream fuse blowing during cold start; detects output faults within 100ns via dedicated ISN2/ISP2 path. |
Use Scenario: Protecting sensitive downstream circuitry (e.g., ADCs, sensors) from overcurrent in portable medical devices. IC Role / Device Role / Timing Role: SEPIC converter with ISP1/ISN1 sensing input current and ISP2/ISN2 sensing output current simultaneously. Use Value: Guarantees ≤3A input surge during startup and ≤300mA output fault current-enabling Class II safety compliance without fuses. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#PBF | Single-channel current sense (100mV), no dual IADJ pins; supports up to 5A switch current but lacks rail-to-rail current sense input common-mode range. | Suitable for single-rail constant-current applications only; cannot independently regulate two current paths like LT3477IFE#TRPBF. | Select when only one regulated current rail is needed and higher peak switch current (5A) is required. |
| MAX1771ESA+ | Fixed 300kHz frequency; no programmable RT pin; uses external N-channel MOSFET instead of integrated 42V NPN switch. | Requires external gate driver and high-side MOSFET layout; less compact and lower efficiency due to external switch losses. | Select when cost sensitivity outweighs board space constraints and integrated switch functionality is not required. |
Compared with LTC3783EFE#PBF and MAX1771ESA+, LT3477IFE#TRPBF uniquely delivers dual independent current regulation with rail-to-rail sensing, integrated 3A/42V switch, and seamless transition between constant-current and constant-voltage modes-making it optimal for multi-rail LED drivers and fault-tolerant distributed power systems.
Availability
LT3477IFE#TRPBF is available at Aetrix Electronics and suitable for high-reliability LED lighting systems, DSL modem power supplies, distributed telecom power architectures, and input/output current-limited converters requiring stable component supply across extended temperature ranges.
Supply support for LT3477IFE#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 healthcare markets.
The LT3477 product line was designed specifically for high-efficiency, dual-loop constant-current/constant-voltage DC/DC conversion in LED lighting, telecom power, and precision current-source applications demanding extended temperature operation and layout simplicity.
FAQ
What is the operating temperature range of the LT3477IFE#TRPBF?
The LT3477IFE#TRPBF is specified for an operating junction temperature range of –40°C to 125°C, making it suitable for industrial and automotive under-hood applications. This I-grade qualification is confirmed in the Absolute Maximum Ratings table and validated across all electrical characteristics in the datasheet's "Electrical Characteristics" section (Page 3, Note 2).
Does the LT3477IFE#TRPBF support negative output voltages?
Yes, the LT3477IFE#TRPBF supports negative output voltages using inverting, SEPIC, or flyback topologies. Its design exposes both FBP and FBN error amplifier inputs externally, allowing FBN to be tied to GND and FBP to a resistive divider referenced to the negative rail-enabling precise regulation of negative outputs as shown in Figure 3 of the datasheet.
How is the switching frequency set on the LT3477IFE#TRPBF?
The switching frequency of the LT3477IFE#TRPBF is set by an external resistor connected between the RT pin (Pin 4) and GND. Values from 2.43kΩ to 107kΩ yield frequencies from 3.5MHz down to 200kHz, as tabulated in Table 4 (Page 11). Leaving RT open is prohibited and will cause malfunction.
What is the purpose of the IADJ1 and IADJ2 pins on the LT3477IFE#TRPBF?
The IADJ1 and IADJ2 pins on the LT3477IFE#TRPBF allow linear adjustment of the current sense thresholds for the two independent current sense amplifiers. Applying a DC voltage below 625mV scales the 100mV default threshold downward (e.g., 309mV → 50mV), enabling fine-grained current control without changing sense resistors-critical for LED brightness or battery charge current tuning.
Can the LT3477IFE#TRPBF drive LEDs in buck mode?
Yes, the LT3477IFE#TRPBF can drive LEDs in buck mode, as demonstrated in Figure 8a of the datasheet. In this configuration, the device regulates LED current via the ISP1/ISN1 sense path while using FBN as the feedback node, enabling high-efficiency, high-current LED driving from input voltages exceeding the LED string voltage-ideal for automotive headlight or industrial lighting systems.
LT3477IFE#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 ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
LT3477IFE#TRPBF FAQ
1.How can I place an order for LT3477IFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3477IFE#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 LT3477IFE#TRPBF reliable?
The price and inventory of LT3477IFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3477IFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3477IFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3477IFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3477IFE#TRPBF?
LT3477IFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3477IFE#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 LT3477IFE#TRPBF?
For technical support, including LT3477IFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3477IFE#TRPBF requirements.
6.How does Aetrix verify that LT3477IFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3477IFE#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 LT3477IFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3477IFE#TRPBF?
All LT3477IFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3477IFE#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 LT3477IFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3477IFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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