My Inquiry
My Account
Analog Devices Inc. LT3477IUF#TRPBF
- Part No.:
- LT3477IUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LT3477IUF#TRPBF.pdf
- Description:
- IC LED DRIVER RGLTR PWM 3A 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,354
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT3477IUF#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 2.5V–25V input, and operates at programmable frequencies from 200kHz to 3.5MHz. It enables constant-current/constant-voltage regulation for high-power LED drivers in boost, buck-boost, or inverting topologies.
For engineers reviewing the LT3477IUF#TRPBF datasheet, LT3477IUF#TRPBF pinout, LT3477IUF#TRPBF application, or LT3477IUF#TRPBF equivalent, key selection criteria include dual 100mV current sense thresholds, thermally enhanced 4mm × 4mm QFN package with exposed PGND pad, ±40°C to +125°C operating range, and independent IADJ1/IADJ2 pins for precision current level adjustment in LED and battery charging systems.
Technical Context
The LT3477IUF#TRPBF implements fixed-frequency current-mode control with three feedback paths: one voltage loop (via FBP/FBN) and two independent current loops (via ISP1/ISN1 and ISP2/ISN2), each regulated to 100mV by dedicated rail-to-rail amplifiers. Its SR-latch PWM comparator compares oscillator ramp plus sensed switch current against VC voltage to set peak current.
It supports bipolar output configurations-positive (FBP tied to VREF) or negative (FBN tied to GND)-and integrates programmable soft-start (9µA SS pin current), external frequency setting (RT pin), and dual current sense adjustability (IADJ1/IADJ2 < 625mV linearly scales sense threshold). The 20-pin QFN exposes PGND on Pin 21 for thermal and electrical integrity.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 25V - supports wide industrial and automotive supply rails without pre-regulation. |
| Switch Rating | 3A, 42V NPN - enables high-current boost and inverting converters up to 42V output or negative rail generation. |
| Current Sense Threshold | 100mV per amplifier (E/I grade: 97.5–103mV) - enables precise, low-loss current sensing with 0.3Ω RSENSE yielding 333mA full-scale. |
| Switching Frequency Range | 200kHz to 3.5MHz (RT-programmable) - allows trade-off between EMI suppression (low f) and component size (high f). |
| Reference Voltage | 1.235V (I-grade min/max: 1.210V/1.260V) - sets output voltage accuracy in CV mode via resistive divider on FBP/FBN. |
| Operating Temperature | –40°C to +125°C junction - qualified for under-hood, industrial, and high-reliability embedded power applications. |
| Package | 20-lead 4mm × 4mm QFN with exposed PGND pad - provides low θJA = 37°C/W for sustained 3A operation without heatsink. |
Pinout & Package
LT3477IUF#TRPBF is housed in a thermally enhanced 20-lead plastic QFN (4mm × 4mm) with exposed power ground (PGND) pad (Pin 21), requiring soldering to PCB ground plane for rated thermal performance and electrical return path.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 3) | Input Supply | Primary power input for internal circuitry; must be locally bypassed with low-ESR ceramic capacitor. |
| RT (Pin 4) | Frequency Set | Connects external resistor to GND to program switching frequency from 200kHz–3.5MHz; open-circuit prohibited. |
| SHDN (Pin 5) | Enable Control | Active-high shutdown: ≥2V enables, ≤0.3V disables; draws ≤1µA in shutdown state. |
| SS (Pin 6) | Soft-Start | Sinks 9µA to charge external capacitor; controls VC ramp rate to limit inrush current during startup. |
| VC (Pin 7) | Error Amplifier Output | Compensation node; connects RC network (e.g., 1kΩ + 4.7nF) to stabilize voltage/current loops. |
| FBN (Pin 8) | Inverting Feedback Input | Connects to resistive divider tap for positive-output CV regulation; bias current ≤100nA. |
| FBP (Pin 9) | Noninverting Feedback Input | Connects to resistive divider tap for negative-output CV regulation; bias current ≤100nA. |
| VREF (Pin 10) | Bandgap Reference | 1.235V reference output; supplies up to 100µA; bypass with 100pF for noise immunity. |
| IADJ1 (Pin 11) | Current Sense 1 Adjust | Linearly scales ISP1/ISN1 sense threshold from 100mV down when <625mV applied; >650mV defaults to 100mV. |
| IADJ2 (Pin 12) | Current Sense 2 Adjust | Same function as IADJ1 for ISP2/ISN2; enables independent dual-current regulation (e.g., parallel LED strings). |
| ISP1/ISN1 (Pins 15/16) | Current Sense 1 Inputs | Differential inputs for first rail-to-rail current amplifier; tolerate common-mode up to 42V. |
| ISP2/ISN2 (Pins 13/14) | Current Sense 2 Inputs | Differential inputs for second rail-to-rail current amplifier; identical specs to ISP1/ISN1. |
| GND (Pin 17) | Analog Ground | Signal ground reference for error amplifier and bias circuits; separate from PGND (Pin 21). |
| SW (Pins 18,19) | Power Switch Collector | High-di/dt node connecting to inductor and diode; requires minimal trace area and tight layout to reduce EMI. |
| NC (Pins 1,2,20) | No Connect | Internally unconnected; may be tied to GND, VIN, or left floating without impact. |
| Exposed Pad (Pin 21) | Power Ground (PGND) | Mandatory solder connection to PCB ground plane for thermal dissipation (θJA = 37°C/W) and switch return path. |
Key Features
| Feature | Design Value |
|---|---|
| Dual rail-to-rail current sense | Two independent 100mV-threshold amplifiers enable simultaneous regulation of two LED strings or input/output current limiting. |
| Wide input voltage range | 2.5V–25V operation eliminates need for pre-regulators in 3.3V, 5V, 12V, and 24V systems. |
| Programmable soft-start | 9µA SS pin current charges external capacitor to linearly ramp VC, preventing inductor saturation and output overshoot. |
| Positive/negative output capability | Separate FBP/FBN inputs allow flexible topology support: boost (positive), inverting (negative), SEPIC, or flyback. |
| Thermally enhanced QFN | 4mm × 4mm package with exposed PGND pad achieves 37°C/W θJA - sustains 3A continuous current at +125°C ambient. |
Applications
| LED Driver for Automotive Lighting | Industrial Input Current-Limited Boost Converter |
|---|---|
|
Use Scenario: Driving 4-series white LEDs from 5V supply in headlamp or DRL module with PWM dimming. IC Role / Device Role / Timing Role: Constant-current DC/DC controller regulating LED string current to 300mA via ISP1/ISN1; uses IADJ1 for factory calibration. Use Value: Achieves 500:1 dimming ratio at 100Hz PWM while maintaining chromaticity; 93% efficiency reduces thermal load in sealed housing. |
Use Scenario: Boosting 12V input to 24V for PoE-powered equipment with strict input surge limits. IC Role / Device Role / Timing Role: Input current limiter using ISP1/ISN1 to cap inrush to 2.5A during hot-plug events; FBN/FBP regulate output voltage. Use Value: Prevents upstream fuse tripping and protects input capacitors; dual-loop architecture ensures stable transition between CC/CV modes. |
| Negative Rail Generator for Op-Amp Bias | Dual-String Constant-Current Source for UV-C LED Arrays |
|
Use Scenario: Generating –15V rail from +12V supply for precision analog front-end requiring dual-supply op-amps. IC Role / Device Role / Timing Role: Inverting converter configured with FBN tied to GND and FBP connected to divider; SW node drives inductor/diode to negative output. Use Value: Eliminates need for isolated DC/DC or charge pump; rail-to-rail current sense ensures accurate load regulation across temperature. |
Use Scenario: Powering two independent UV-C LED strings (350mA each) from 24V supply in sterilization system. IC Role / Device Role / Timing Role: Dual current regulator using ISP1/ISN1 and ISP2/ISN2 with separate IADJ1/IADJ2 pins for independent brightness control. Use Value: Enables asymmetric dimming (e.g., 100% + 60%) without cross-talk; 100mV sense threshold minimizes power loss in high-current shunts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC/DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3787IUF#PBF | 4-switch synchronous buck-boost controller (external MOSFETs); no integrated switch; supports 4–36V input; 100mV current sense not rail-to-rail. | Requires external power stage; better suited for >5A, high-efficiency buck-boost where layout control is critical. | Select LTC3787IUF#PBF when higher output current (>3A), synchronous rectification, or input voltage exceeding 25V is required. |
| LT3757AIMSE#TRPBF | Current-mode boost/SEPIC/flyback controller (no integrated switch); 100V switch driver; 50mV current sense threshold; no dual current sense. | Designed for high-voltage outputs (>100V); lacks second current sense amplifier and IADJ pins. | Select LT3757AIMSE#TRPBF for >60V output applications like APD bias or industrial lighting where dual current regulation is unnecessary. |
Compared with LTC3787IUF#PBF and LT3757AIMSE#TRPBF, the LT3477IUF#TRPBF uniquely integrates a 3A/42V switch and dual rail-to-rail 100mV current sense amplifiers in a compact QFN, making it optimal for space-constrained, dual-string constant-current LED drivers and bipolar rail generation below 25V input.
Availability
LT3477IUF#TRPBF is available at Aetrix Electronics and suitable for high-reliability LED driver, industrial power conversion, and negative rail generation applications requiring stable component supply across extended temperature ranges.
Supply support for LT3477IUF#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.
The LT3477 belongs to Linear's high-efficiency DC/DC converter product line, designed specifically for constant-current/constant-voltage applications including LED drivers, battery chargers, and industrial power supplies demanding precision current regulation and wide input range.
FAQ
What is the maximum output voltage achievable with LT3477IUF#TRPBF in boost configuration?
The LT3477IUF#TRPBF supports output voltages up to 42V in boost mode, limited by its internal 42V NPN switch's collector-emitter breakdown rating. Practical maximum depends on external diode reverse voltage rating, inductor saturation current, and layout parasitics-but design examples confirm stable 36V output at 300mA with 5V input. Always maintain ≥20% margin below 42V for reliability.
Does LT3477IUF#TRPBF support true zero-current shutdown?
Yes. When SHDN is pulled below 0.3V, the LT3477IUF#TRPBF enters full shutdown with quiescent current ≤0.1µA (typical), and the internal switch is fully disabled. No current flows through SW, and VC, SS, and reference circuits are powered down - enabling battery-powered systems to achieve nanoamp-level standby consumption.
How does the dual current sense architecture of LT3477IUF#TRPBF improve LED driver reliability?
The dual rail-to-rail current sense amplifiers in LT3477IUF#TRPBF independently monitor two LED strings or input/output currents. This enables open-LED protection (one string open → other remains lit), redundant current limiting, and asymmetric dimming without interaction. Each amplifier's 100mV threshold minimizes shunt power loss and improves accuracy over temperature versus higher-threshold alternatives.
Can LT3477IUF#TRPBF be used in SEPIC topology, and what are the key layout considerations?
Yes - the LT3477IUF#TRPBF supports SEPIC via its dual feedback capability: FBN regulates output voltage while ISP1/ISN1 limits input current. Critical layout requirements include minimizing loop area of the coupled inductor's two windings, placing input/output capacitors close to respective nodes, and routing the crossover capacitor (CSEPIC) with short, low-inductance traces to prevent ringing and EMI.
What is the role of the exposed pad (Pin 21) on LT3477IUF#TRPBF, and is it electrically connected?
The exposed pad (Pin 21) on LT3477IUF#TRPBF is Power Ground (PGND), directly connected to the internal switch emitter and thermal slug. It must be soldered to a solid PCB ground plane to achieve specified θJA = 37°C/W and ensure safe 3A operation. Leaving it unconnected causes thermal runaway and premature failure - it is not optional or floating.
LT3477IUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-WFQFN 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-QFN (4x4)
LT3477IUF#TRPBF FAQ
1.How can I place an order for LT3477IUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3477IUF#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 LT3477IUF#TRPBF reliable?
The price and inventory of LT3477IUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3477IUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3477IUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3477IUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3477IUF#TRPBF?
LT3477IUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3477IUF#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 LT3477IUF#TRPBF?
For technical support, including LT3477IUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3477IUF#TRPBF requirements.
6.How does Aetrix verify that LT3477IUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3477IUF#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 LT3477IUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3477IUF#TRPBF?
All LT3477IUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3477IUF#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 LT3477IUF#TRPBF part is unused and in its original packaging.
Return procedure for LT3477IUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3477IUF#TRPBF Tags
-
BCR402RE6327HTSA1
Infineon Technologies
-
BCR430UXTSA2
Infineon Technologies
-
BCR420UE6433HTMA1
Infineon Technologies
-
BCR420UE6327HTSA1
Infineon Technologies
-
BCR421UE6327HTSA1
Infineon Technologies
-
LYT1604D-TL
Power Integrations
-
HV9910CLG-G
Microchip Technology
-
CL2N8-G
Microchip Technology
-
BCR420UW6-7
Diodes Incorporated
-
BCR421UW6-7
Diodes Incorporated
-
BCR420UFD-7
Diodes Incorporated
-
BCR421UFD-7
Diodes Incorporated
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
