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Analog Devices Inc. LT3745IUJ#PBF
- Part No.:
- LT3745IUJ#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 40-WFQFN Exposed Pad
- Datasheet:
-
LT3745IUJ#PBF.pdf
- Description:
- IC LED DRVR CTRLR PWM 75MA 40QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,015
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Product details
Overview
LT3745IUJ#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 LT3745IUJ#PBF datasheet, LT3745IUJ#PBF pinout, LT3745IUJ#PBF application, or LT3745IUJ#PBF equivalent, key selection criteria include its 40-lead 6mm × 6mm QFN package, 6-bit dot correction per channel, open/short LED fault diagnostics, ±1% typical current mismatch, and thermal shutdown via TSET pin programming.
Technical Context
The LT3745IUJ#PBF integrates a nonsynchronous current-mode buck controller with sixteen linear current sinks. The buck stage regulates an adaptive output bus voltage (up to 36V) based on feedback from the FB pin and inductor current sensing via ISP/ISN pins, while each LED channel uses precision current mirroring referenced to ISET.
Its 6-wire serial interface (SCKI/SDI/LDI/SCKO/SDO/LDO) enables skew-balanced, cascadable communication at 30MHz without external clock buffers. Internal registers include sixteen 12-bit grayscale PWM counters and sixteen 6-bit dot correction DACs, all accessible via TTL/CMOS-level signals with 2.4V high-level threshold and 0.6V low-level threshold.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 6V to 55V input - supports wide-range industrial and display power rails including 12V, 24V, and 48V systems. |
| LED Current per Channel | 25mA to 75mA (typ 50mA) - set by external ISET resistor; enables uniform brightness across 16 parallel strings. |
| Current Matching | ±3% (typ ±1%) - ensures consistent luminance across channels without manual calibration. |
| PWM Dimming Resolution | 12-bit grayscale - provides 4096-step intensity control for smooth video-grade dimming at 500Hz. |
| Serial Interface Speed | 30MHz clock (SCKI) - allows rapid configuration of all 16 channels and status readback in under 7µs per frame. |
| Min LED On-Time | 0.5µs - supports high-frequency PWM without pulse truncation, critical for fast-refresh displays. |
| Package | 40-lead 6mm × 6mm QFN with exposed pad - optimized for thermal dissipation in high-current LED driver applications. |
Pinout & Package
LT3745IUJ#PBF is housed in a 40-lead plastic QFN package (6mm × 6mm) with exposed thermal pad (Pin 41), which must be soldered to PCB ground for thermal management and electrical stability.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO (1) | Enable & undervoltage lockout input | Logic-enable control and programmable VIN UVLO threshold; tie to VCC if unused. |
| LED00–LED15 (2–9, 22–29) | Constant-current sink outputs | Drive LED string cathodes; each supports up to 36V reverse voltage and 75mA sink current. |
| VCC (15) | Logic supply | Powers serial interface and internal logic; requires local 10µF bypass to GND. |
| SCKI/SDI/LDI (11,13,14) | Serial data input interface | TTL/CMOS-compatible inputs for cascaded configuration; LDI latches data into registers. |
| SCKO/SDO/LDO (20,18,17) | Serial data output interface | Skew-balanced outputs for daisy-chaining; eliminate need for external clock buffers. |
| ISET (40) | Nominal LED current reference | Resistor-to-ground sets all 16 channels' base current; 60.4kΩ yields ~50mA. |
| TSET (39) | Overtemperature threshold | Resistor-to-ground programs thermal shutdown point; 46.4kΩ sets ~125°C trip. |
| ISP/ISN (35,34) | Buck inductor current sense | Differential pair for peak-current-mode control; 46.5mV threshold enables precise cycle-by-cycle limiting. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive LED bus voltage | Automatically adjusts buck output to minimum required for longest LED string - improves system efficiency by >15% vs fixed-voltage supplies. |
| Full LED fault diagnostics | Individual open-circuit and short-circuit detection per channel, plus overtemperature flag - enables real-time display health monitoring and fail-safe shutdown. |
| 6-bit per-channel dot correction | Independent current trimming for each of 16 outputs - compensates for LED binning and aging drift without firmware recalibration. |
| 30MHz cascadable serial interface | 6-wire topology (SCKI/SDI/LDI/SCKO/SDO/LDO) eliminates inter-chip skew - supports >100 devices in series with no timing margin loss. |
| 0.5µs minimum LED on-time | Enables high-frequency PWM without pulse distortion - essential for flicker-free operation in video-rate displays (≥240Hz refresh). |
Applications
| Large-Screen LCD Backlighting | Mono-/Full-Color LED Displays |
|---|---|
Use Scenario: Dynamic local dimming in 55-inch+ LCD TVs and digital signage using hundreds of individually controlled LED zones. IC Role / Device Role / Timing Role: LT3745IUJ#PBF acts as zone driver IC - each device controls 16 LED strings, synchronized via PWMCK to match panel refresh rate. Use Value: Enables >10,000:1 contrast ratio through per-zone brightness modulation, leveraging 12-bit dimming resolution and adaptive bus voltage. | Use Scenario: Pixel-level brightness control in outdoor LED billboards with RGB modules requiring precise color fidelity. IC Role / Device Role / Timing Role: LT3745IUJ#PBF serves as RGB channel driver - three devices (one per R/G/B) drive 48 LEDs per module with matched current and timing. Use Value: ±1% typical current matching ensures stable white point across thousands of pixels; 6-bit dot correction maintains color consistency over lifetime. |
| LED Video Walls | Industrial HMI Displays |
Use Scenario: High-reliability indoor video walls in broadcast studios where uptime and thermal stability are critical. IC Role / Device Role / Timing Role: LT3745IUJ#PBF functions as thermal-aware LED controller - TSET pin monitors die temperature and triggers graceful dimming before shutdown. Use Value: Prevents hot-spot failure during sustained high-brightness operation; overtemperature flag feeds back to system controller for predictive maintenance. | Use Scenario: Embedded operator interfaces in factory automation panels requiring sunlight-readable brightness and long service life. IC Role / Device Role / Timing Role: LT3745IUJ#PBF operates as compact LED driver - integrated buck + 16-channel sink reduces BOM count vs discrete solutions. Use Value: Single-chip solution cuts board space by >40% vs dual-IC approach; QFN package withstands industrial vibration and thermal cycling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3745EUJ#PBF | Same silicon, rated for 0°C to 125°C junction temperature (vs –40°C to 125°C for LT3745IUJ#PBF); lower guaranteed current matching spec (±3% only, no ±1% typ). | Not suitable for extended industrial environments below 0°C; acceptable for commercial indoor displays. | Select LT3745IUJ#PBF when operating ambient exceeds 85°C or cold-start reliability below –25°C is required. |
| MAX16834ATL+T | 16-channel 50mA LED driver with integrated boost controller (not buck); lacks 30MHz serial interface and dot correction; uses SPI instead of proprietary 6-wire protocol. | Requires external microcontroller for register access; no built-in open/short LED diagnostics; limited to boost-based topologies. | Choose MAX16834ATL+T only when boost architecture is mandated and diagnostic depth is secondary to cost. |
Compared with LT3745EUJ#PBF, the LT3745IUJ#PBF offers guaranteed operation down to –40°C and tighter typical current matching; versus MAX16834ATL+T, it provides superior integration (buck + diagnostics + dot correction + high-speed interface) but requires adherence to its specific 6-wire cascade layout.
Availability
LT3745IUJ#PBF is available at Aetrix Electronics and suitable for large-screen LCD backlighting, mono-/full-color LED displays, LED video walls, industrial HMI displays, and outdoor signage requiring stable component supply and long-term production continuity.
Supply support for LT3745IUJ#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 product support, documentation, and manufacturing continuity for the LT® family.
The LT3745IUJ#PBF belongs to Linear's high-performance LED driver product line, engineered specifically for demanding display applications requiring precision current regulation, advanced diagnostics, and scalable serial control.
FAQ
What is the maximum number of LT3745IUJ#PBF devices that can be cascaded reliably?
The LT3745IUJ#PBF supports robust cascading via its 6-wire skew-balanced interface. At 30MHz SCKI, up to 32 devices can be daisy-chained while maintaining timing margins; at 15MHz, more than 100 devices are feasible. Layout best practices-such as matched-length routing of SCKO/SDO/LDO and minimizing stubs-ensure signal integrity across the chain. Each LT3745IUJ#PBF contributes deterministic propagation delay (≤40ns), enabling predictable system-level timing analysis.
How does the LT3745IUJ#PBF achieve ±3% LED current matching across channels?
The LT3745IUJ#PBF achieves ±3% LED current matching through laser-trimmed internal current references and matched transistor arrays fabricated on a single die. Each channel's sink current is derived from the same ISET reference voltage (1.205V typ), routed through precision-matched mirror transistors. Process variation is minimized by common-centroid layout and on-chip thermal coupling. The ±1% typical matching is measured at 50mA per channel under thermal equilibrium conditions, as confirmed in the Electrical Characteristics table.
Can the LT3745IUJ#PBF drive LEDs with forward voltages exceeding 36V per string?
No - the absolute maximum LEDxx pin voltage rating is 40V, and the recommended operating limit is 36V per channel, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Exceeding 36V risks violating the ISP/ISN common-mode range (0V to 36V) and may compromise current regulation accuracy or trigger overvoltage protection. For higher-VF strings, use multiple LT3745IUJ#PBF devices in series or select a higher-voltage driver like the LT3761.
What is the function of the TSET pin on the LT3745IUJ#PBF, and how is it configured?
The TSET pin on the LT3745IUJ#PBF programs the overtemperature shutdown threshold via an external resistor to ground. A current source (19.8µA typ) flows through the resistor, generating a voltage that is compared internally to a temperature-dependent reference. For example, a 46.4kΩ resistor yields ~928mV, corresponding to a junction temperature trip point near 125°C. The relationship is linear and documented in the Typical Performance Characteristics plot "TSET Threshold vs Temperature". This enables customizable thermal protection without external sensors.
Does the LT3745IUJ#PBF support both DC and PWM dimming modes?
Yes - the LT3745IUJ#PBF supports two independent dimming methods: 6-bit dot correction (DC dimming) for coarse, static current adjustment per channel, and 12-bit grayscale PWM dimming for fine, dynamic intensity control. Dot correction values are loaded via the DC frame; PWM duty cycles are set in the GS frame. Both operate simultaneously: DC sets the baseline current (e.g., 50mA), and PWM modulates it (e.g., 0–100% of 50mA). This dual-stage approach enables >16-bit effective resolution and eliminates visible steps in brightness transitions.
LT3745IUJ#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)
LT3745IUJ#PBF FAQ
1.How can I place an order for LT3745IUJ#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3745IUJ#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 LT3745IUJ#PBF reliable?
The price and inventory of LT3745IUJ#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3745IUJ#PBF is usually 5 days.
3.What payment methods are accepted for LT3745IUJ#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3745IUJ#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3745IUJ#PBF?
LT3745IUJ#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3745IUJ#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 LT3745IUJ#PBF?
For technical support, including LT3745IUJ#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3745IUJ#PBF requirements.
6.How does Aetrix verify that LT3745IUJ#PBF is sourced from the original manufacturer or authorized distributors?
All LT3745IUJ#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 LT3745IUJ#PBF meets industry standards.
7.What is the process for return or replacement of LT3745IUJ#PBF?
All LT3745IUJ#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3745IUJ#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 LT3745IUJ#PBF part is unused and in its original packaging.
Return procedure for LT3745IUJ#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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