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Analog Devices Inc. LT3745EUJ#PBF
- Part No.:
- LT3745EUJ#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 40-WFQFN Exposed Pad
- Datasheet:
-
LT3745EUJ#PBF.pdf
- Description:
- IC LED DRVR CTRLR PWM 75MA 40QFN
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LT3745EUJ#PBF from Analog Devices (formerly Linear Technology) is a 16-channel, 50mA constant-current LED driver with integrated 55V buck controller for adaptive LED bus voltage generation. It delivers ±3% LED current matching at 50mA per channel, supports 12-bit grayscale PWM dimming up to 500Hz, and features a 30MHz cascadable serial interface. It is designed for high-precision dynamic backlighting in large-screen LCDs and full-color LED displays.
For engineers reviewing the LT3745EUJ#PBF datasheet, LT3745EUJ#PBF pinout, LT3745EUJ#PBF application, or LT3745EUJ#PBF equivalent, key selection criteria include its 40-lead 6mm × 6mm QFN package, 6-bit per-channel dot correction, ±3% current matching, 0.5µs minimum LED on-time, and cascaded 6-wire serial topology enabling scalable display systems without external clock buffers.
Technical Context
The LT3745EUJ#PBF integrates a current-mode nonsynchronous buck controller with sixteen linear current sinks. The buck stage regulates an adaptive output bus voltage (via FB pin and resistor divider), while each LED channel uses a precision current sink with programmable ISET and TSET pins. Its internal 1.205V reference governs both FB regulation and ISP/ISN current-sense threshold (34–59mV).
Operation relies on three synchronized timing domains: RT-programmed oscillator (200kHz–1MHz), 30MHz SCKI-driven serial interface with skew-balanced LDO/SCKO/SDO outputs, and PWMCK-synchronized 12-bit grayscale counters. Fault detection (open/short LED, overtemperature) is reported via the same serial interface using status frames.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 6V to 55V input - supports wide-range industrial and automotive LED power rails. |
| LED Current per Channel | 25mA to 75mA (typ. 50mA) - set by external RISET resistor; enables uniform brightness across 16 strings. |
| Current Matching | ±3% (typ. ±1%) - ensures consistent luminance across all 16 channels without manual calibration. |
| PWM Dimming Resolution | 12-bit grayscale - delivers 4096-step intensity control for smooth video-grade dimming. |
| Serial Interface Speed | 30MHz clock (SCKI) - enables fast frame updates for large displays with minimal latency. |
| Min LED On-Time | 0.5µs - supports high-frequency PWM without pulse truncation, critical for low-brightness fidelity. |
| Package | 40-lead 6mm × 6mm QFN with exposed pad - provides thermal performance for continuous 50mA/channel operation. |
Pinout & Package
LT3745EUJ#PBF is housed in a 40-lead plastic QFN (UJ package), 6mm × 6mm, with exposed thermal pad (Pin 41) soldered to PCB ground. Pin functions are validated per Linear Technology's official datasheet (3745f) and confirmed on Analog Devices' product page.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO (1) | Enable & Input UVLO Input | Shuts down chip below 0.35V; enables above 1.34V; also programs VIN UVLO via resistor divider. |
| LED00–LED15 (2–9, 22–29) | LED Cathode Sink Outputs | 16 independent constant-current sinks - connect LED string cathodes directly; each supports up to 36V reverse voltage. |
| VIN (38), GATE (37), CAP (36), ISP/ISN (35/34), FB (33) | Buck Controller Power & Sense | Forms complete nonsynchronous buck stage: VIN powers gate driver via CAP-regulated 6.8V rail; ISP/ISN sense inductor current; FB sets adaptive bus voltage. |
| ISET (40), TSET (39) | Current & Thermal Threshold Set | ISET resistor programs nominal LED current; TSET resistor sets overtemperature shutdown threshold (510mV trip point). |
| SCKI/SDI/LDI/SCKO/SDO/LDO (11,13,14,20,18,17) | 6-Wire Serial Interface | Enables cascadable daisy-chain: SCKI/SDI/LDI drive in; SCKO/SDO/LDO drive next device - eliminates global clock routing and skew compensation. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive LED Bus Voltage | Reduces power loss by dynamically adjusting buck output to just exceed the highest forward voltage among 16 LED strings. |
| 6-Bit Dot Correction | Per-channel current trim (64 steps) compensates for LED binning and trace resistance variation - improves display uniformity without hardware changes. |
| Full Diagnostic Reporting | Real-time open/short LED and overtemperature fault flags returned via serial status frame - enables system-level health monitoring and fail-safe response. |
| Thermally Optimized QFN | Exposed pad (Pin 41) must be soldered to solid ground plane - achieves θJC = 2.5°C/W, supporting 125°C junction operation at full load. |
| UVLO Protection | Triple independent UVLO: VCC (2.82V rise), EN/UVLO (0.35V rise), and (VIN–VCAP) (4.6V rise) - prevents erratic startup under brownout conditions. |
Applications
| Large-Screen LCD Backlighting | Mono- and Full-Color LED Displays |
|---|---|
Use Scenario: Dynamic local dimming in 55-inch+ LCD TVs using 16 parallel LED zones per LT3745EUJ#PBF, updated at 500Hz. IC Role / Device Role / Timing Role: LT3745EUJ#PBF acts as zone-specific current controller and bus voltage manager; PWMCK synchronizes grayscale timing across all 16 channels. Use Value: Enables >10,000:1 contrast ratio via per-zone dimming while maintaining ±3% brightness uniformity across the panel. | Use Scenario: Pixel-level intensity control in outdoor RGB LED signage with cascaded LT3745EUJ#PBF arrays driving 256×128 pixel modules. IC Role / Device Role / Timing Role: LT3745EUJ#PBF serves as 16-pixel sub-driver; 30MHz SCKI and cascadable SCKO/SDO/LDO enable single-controller synchronization of >100 devices. Use Value: Eliminates external clock buffers and reduces PCB routing complexity - cuts BOM cost and layout time for high-density displays. |
| LED Billboards | Industrial HMI Panels |
Use Scenario: High-reliability outdoor advertising displays operating continuously at 55°C ambient, requiring thermal fault detection and open-LED redundancy. IC Role / Device Role / Timing Role: LT3745EUJ#PBF monitors each LED string via ISP/ISN and reports faults via serial status frame; TSET resistor configures 85°C shutdown threshold. Use Value: Prevents catastrophic failure from single-string opens - maintains partial display functionality and triggers maintenance alerts. | Use Scenario: Medical or factory-floor HMIs where flicker-free dimming and EMI-controlled switching are mandatory. IC Role / Device Role / Timing Role: LT3745EUJ#PBF implements 500Hz 12-bit PWM dimming with 0.5µs on-time resolution; buck frequency set to 1MHz (RT=46.4kΩ) minimizes conducted noise. Use Value: Meets IEC 61000-3-2 harmonic limits and eliminates perceptible flicker in critical visual environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver with buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3761EUFD#PBF | Single-channel 100mA LED driver + 60V buck; no dot correction or multi-channel PWM; uses analog dimming or basic PWM. | Best for high-current single-string designs (e.g., automotive headlights); lacks serial interface and channel count for display backlighting. | Select LT3761EUFD#PBF only when driving one high-power LED string and system-level brightness control suffices. |
| MAX20050ATP/V+T | 4-channel 150mA LED driver + 65V buck; I²C interface (not cascadable); no dot correction; ±5% current matching. | Suitable for compact automotive clusters or small displays; limited channel count and lower matching accuracy than LT3745EUJ#PBF. | Choose MAX20050ATP/V+T for space-constrained designs needing I²C integration but not large-scale cascading or precision uniformity. |
Compared with LT3745EUJ#PBF, LT3761EUFD#PBF trades channel count and digital control for higher per-channel current, while MAX20050ATP/V+T offers smaller footprint and I²C compatibility at the expense of scalability and matching precision - making LT3745EUJ#PBF uniquely suited for high-channel-count, high-uniformity display systems.
Availability
LT3745EUJ#PBF is available at Aetrix Electronics and suitable for large-screen LCD backlighting, mono/multi-color LED displays, LED billboards, and industrial HMI panels requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant lead-free packaging.
Supply support for LT3745EUJ#PBF 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 and maintains full technical and manufacturing continuity for the LT® product family. Linear Technology pioneered high-performance analog ICs for power management and signal conditioning.
The LT3745EUJ#PBF belongs to Linear's LED driver and DC/DC controller product line, engineered specifically for high-accuracy, high-channel-count LED lighting systems demanding adaptive voltage control, diagnostic feedback, and scalable serial communication.
FAQ
What is the maximum number of LT3745EUJ#PBF devices that can be cascaded in series?
The LT3745EUJ#PBF supports daisy-chaining via its 6-wire serial interface (SCKI/SDI/LDI → SCKO/SDO/LDO). At 30MHz SCKI, up to 16 devices can be cascaded before duty-cycle skew limits reliable frame capture. For longer chains, reduce SCKI frequency or add repeater logic. Each LT3745EUJ#PBF contributes 194 bits per frame, so total chain latency scales linearly with device count.
How is LED current set on the LT3745EUJ#PBF, and what resistor value yields 50mA per channel?
LED current is set by an external resistor (RISET) from ISET (Pin 40) to GND. Using the formula ILED = 2500 × 1.205V / RISET, a 60.4kΩ resistor yields 50.0mA (typical). The LT3745EUJ#PBF datasheet specifies ±3% matching at this setting, and the ISET pin voltage remains trimmed to 1.205V across temperature.
Does the LT3745EUJ#PBF require external components for buck converter operation, and what are the critical ones?
Yes - the LT3745EUJ#PBF requires external components for buck operation: a P-channel MOSFET (driven by GATE), power inductor, output capacitor, input capacitor, and ISP/ISN sense resistor. Critical values include: CCAP = 0.47µF (from CAP to VIN), RT = 46.4kΩ (for 1MHz switching), and RFB1/RFB2 to set FB voltage and thus adaptive bus voltage. All are specified in the LT3745EUJ#PBF typical application circuit.
Can the LT3745EUJ#PBF drive LEDs with forward voltages exceeding 36V per string?
No - the absolute maximum rating for LEDxx pins is 40V, and the datasheet specifies "LEDxx Operating Voltage" as 36V (min) under full operating conditions. Driving strings above 36V risks violating safe operating area and invalidates the ±3% current matching guarantee. For higher-voltage strings, use a boost or SEPIC front-end stage ahead of the LT3745EUJ#PBF.
What fault conditions does the LT3745EUJ#PBF detect, and how is fault data retrieved?
The LT3745EUJ#PBF detects open-LED (VLED < 0.35V), short-LED (VLED > 3.9V), and overtemperature (TSET voltage > 510mV) faults. Fault status is embedded in the 194-bit serial status frame returned on SDO after each LDI pulse. The frame includes 16 individual LED fault bits, 1 overtemperature bit, and 16 dot-correction register values - all readable without interrupting normal PWM operation.
LT3745EUJ#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 40-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Controller
- Topology:
- Step-Down (Buck)
- Internal Switch(s):
- No
- Number of Outputs:
- 16
- Voltage - Supply (Min):
- 6V
- Voltage - Supply (Max):
- 55V
- Voltage - Output:
- 36V
- Current - Output / Channel:
- 75mA
- Frequency:
- 200kHz ~ 1MHz
- Dimming:
- PWM
- Applications:
- Backlight, Signage
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 40-QFN (6x6)
LT3745EUJ#PBF FAQ
1.How can I place an order for LT3745EUJ#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3745EUJ#PBF 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 LT3745EUJ#PBF reliable?
The price and inventory of LT3745EUJ#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3745EUJ#PBF is usually 5 days.
3.What payment methods are accepted for LT3745EUJ#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3745EUJ#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3745EUJ#PBF?
LT3745EUJ#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3745EUJ#PBF 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 LT3745EUJ#PBF?
For technical support, including LT3745EUJ#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3745EUJ#PBF requirements.
6.How does Aetrix verify that LT3745EUJ#PBF is sourced from the original manufacturer or authorized distributors?
All LT3745EUJ#PBF 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 LT3745EUJ#PBF meets industry standards.
7.What is the process for return or replacement of LT3745EUJ#PBF?
All LT3745EUJ#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3745EUJ#PBF, 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 LT3745EUJ#PBF part is unused and in its original packaging.
Return procedure for LT3745EUJ#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3745EUJ#PBF Tags
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