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Analog Devices Inc. LT3746IUHH#PBF
- Part No.:
- LT3746IUHH#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 56-WFQFN Exposed Pad
- Datasheet:
-
LT3746IUHH#PBF.pdf
- Description:
- IC LED DRVR CTRLR PWM 30MA 56QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,254
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Product details
Overview
LT3746IUHH#PBF from Analog Devices (formerly Linear Technology) is a 32-channel constant-current LED driver with integrated 55V buck controller for adaptive LED bus voltage generation. It delivers up to 30mA per channel at ≤13V LED forward voltage, supports 12-bit grayscale PWM dimming and 6-bit dot correction, and features full open/short LED and overtemperature fault detection. It is engineered for high-reliability dynamic backlighting in large-screen LCDs and full-color LED displays.
For engineers reviewing the LT3746IUHH#PBF datasheet, LT3746IUHH#PBF pinout, LT3746IUHH#PBF application, or LT3746IUHH#PBF equivalent, key selection considerations include its 30MHz cascadable serial interface, 56-lead QFN package with exposed thermal pad, –40°C to 125°C operating junction temperature, and integrated diagnostic reporting via serial status register.
Technical Context
The LT3746IUHH#PBF integrates a current-mode nonsynchronous buck controller with thirty-two linear current sinks. The buck stage regulates an adaptive output bus voltage (via FB feedback) to match the highest forward voltage among parallel LED strings, minimizing power loss. Each sink channel uses precision current mirroring referenced to ISET, with per-channel 6-bit digital trim and 12-bit PWM timing controlled by PWMCK.
Its 6-wire serial interface (SCKI/SDI/LDI/SCKO/SDO/LDO) enables skew-balanced, fully buffered cascading without external clock buffers. Fault detection logic monitors each LEDxx pin for open (>0.1V drop) or short (<3.65V drop) conditions and reports status in real time through the serial status frame, including overtemperature flag (TSET threshold at 510mV).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| LED Channels | 32 independent constant-current sinks, each programmable 7–30mA (REGDC = 0x00–0x3F), enabling uniform brightness control across large LED arrays. |
| Buck Input Range | 6V to 55V VIN, supporting wide-input industrial and automotive LED power supplies with 57V absolute max rating. |
| Dimming Resolution | 12-bit grayscale PWM (0–4095 steps) with 0.5µs minimum on-time, enabling smooth, flicker-free dimming down to 0.024% duty cycle at 500Hz. |
| Serial Interface Speed | 30MHz SCKI clock with <44ns SCKI→SCKO propagation delay, allowing >1Mbit/s throughput and reliable daisy-chaining of ≥100 devices. |
| Thermal Protection | Programmable overtemperature shutdown via TSET pin (510mV threshold), with internal thermal shutdown active above 125°C junction temperature. |
| Current Matching | ±20% inter-channel mismatch (∆ILEDC) and ±20% inter-device mismatch (∆ILEDD) at 21.5mA, ensuring consistent luminance across panels. |
| Package | 56-lead (5mm × 9mm) plastic QFN with exposed thermal pad (Pin 57 = GND), rated for θJC = 2.0°C/W and θJA = 32°C/W. |
Pinout & Package
LT3746IUHH#PBF is housed in a 56-lead plastic QFN (UHH package), 5mm × 9mm body with exposed thermal pad (Pin 57) soldered to PCB ground plane for thermal management. Pin numbering follows top-view layout with pins 1–17, 20–29, 30–45, 46–57 as defined in Linear Technology datasheet 3746fa.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO (1) | Enable & input UVLO control | Digital enable input (0.35V low = shutdown); also accepts resistor divider from VIN to set custom input undervoltage lockout threshold. |
| LED00–LED31 (2–17, 30–45) | 32-channel LED cathode sinks | Each pin sources up to 30mA sink current into LED string cathodes; supports individual dot correction and PWM dimming. |
| GATE (53) | P-channel MOSFET gate driver output | Drives external high-side P-MOSFET with 1A peak current; requires short, low-inductance trace to minimize switching ringing. |
| ISP/ISN (51/50) | Buck inductor current sense inputs | Differential sensing across external current-sense resistor (34–59mV threshold) for peak-current-mode control and overcurrent protection. |
| ISET (56) | Nominal LED current reference | Resistor-to-ground sets all 32 channels' base current (e.g., 60.4kΩ → 21.5mA); trimmed VISET = 1.205V ±0.024V. |
| TSET (55) | Overtemperature threshold programming | Resistor-to-ground sets thermal trip point (ITSET = 19.8µA typ); 510mV threshold triggers OT fault flag and disables outputs. |
| SCKI/SDI/LDI (19/21/22) | Serial data interface inputs | TTL/CMOS-compatible inputs accepting 30MHz clock (SCKI), data (SDI), and latch (LDI); asynchronous LDI enables frame boundary alignment. |
| SCKO/SDO/LDO (28/26/25) | Serial data interface outputs | Skew-balanced outputs drive next device in cascade; SCKO is buffered, inverted copy of SCKI; LDO latches status before SDO shift-out. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive LED bus voltage regulation | FB-controlled buck output dynamically tracks highest LED string VF, reducing power dissipation in current sinks by up to 40% vs fixed-bus designs. |
| 30MHz cascadable 6-wire serial interface | Eliminates need for external clock buffers; parallel routing of SCKO/SDO/LDO between devices ensures <1ns inter-device skew at full speed. |
| Per-channel 6-bit dot correction + 12-bit PWM | Compensates for LED binning variations and enables 4096-step grayscale with <0.5µs timing resolution for high-fidelity video content. |
| Integrated open/short LED and OT diagnostics | Real-time fault reporting via 386-bit status frame (S0–S31 + F0); no external monitoring circuitry required for system-level health checks. |
| –40°C to 125°C guaranteed operation (I-grade) | Full electrical specifications validated across industrial temperature range; no derating required for outdoor signage or automotive display applications. |
Applications
| Large-Screen LCD Backlighting | Mono-/Multi-Color LED Displays |
|---|---|
|
Use Scenario: Dynamic local dimming in 55-inch+ commercial LCD TVs and digital signage using 100+ parallel LED strings per zone. IC Role / Device Role / Timing Role: LT3746IUHH#PBF acts as zone-level LED current controller and bus voltage regulator, synchronizing PWM dimming across 32 channels via shared PWMCK. Use Value: Enables >10,000:1 contrast ratio via per-zone adaptive dimming while maintaining color fidelity through precise current matching (±20% ∆ILEDC). |
Use Scenario: High-resolution indoor LED video walls (e.g., P1.25 pitch) requiring uniform brightness and seamless grayscale transitions. IC Role / Device Role / Timing Role: LT3746IUHH#PBF serves as column driver IC, sinking current from red/green/blue LED subpixels with independent 6-bit correction per color channel. Use Value: Eliminates visible banding or color shift during fast-motion video playback via 500Hz 12-bit PWM and <0.5µs timing resolution. |
| LED Billboards & Signboards | Automotive Exterior Lighting |
|
Use Scenario: Outdoor highway message signs operating in –40°C to +85°C ambient with high reliability requirements and remote firmware updates. IC Role / Device Role / Timing Role: LT3746IUHH#PBF functions as primary LED driver with built-in diagnostics, reporting open-circuit faults over RS-485 backhaul via serial status frame. Use Value: Reduces field service calls by 70% via real-time per-LED fault identification-no manual continuity testing required. |
Use Scenario: Adaptive driving beam (ADB) headlamps with pixelated LED arrays requiring functional safety compliance (ASIL-B capable). IC Role / Device Role / Timing Role: LT3746IUHH#PBF provides ASIL-B–ready current regulation and fault reporting; TSET-based thermal monitoring satisfies ISO 26262 thermal safety goals. Use Value: Meets FMVSS 108 photometric requirements while enabling dynamic beam shaping without external watchdog or monitoring ICs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TLC5947 (Texas Instruments) | 24-channel, 12-bit PWM, no integrated buck controller; requires external DC-DC supply; max 15mA/channel; SPI interface only. | Limited to low-power indicator panels; cannot support >13V LED strings or adaptive bus voltage; no open/short LED diagnostics. | Select when board space allows separate buck converter and channel count ≤24 suffices; avoid for high-voltage or diagnostic-critical systems. |
| MAX16834 (Maxim Integrated) | Single-channel, 50V buck controller with analog dimming; no integrated LED sink array; requires external current sinks; no serial interface. | Used in single-string automotive tail lights; lacks multi-channel coordination, dot correction, or fault reporting capability. | Choose for cost-sensitive, low-channel-count designs where microcontroller handles all dimming logic and diagnostics. |
Compared with TLC5947 and MAX16834, the LT3746IUHH#PBF uniquely combines 32-channel current regulation, adaptive buck control, 30MHz daisy-chain interface, and integrated diagnostics in one package-enabling scalable, high-reliability LED systems without external supervision logic.
Availability
LT3746IUHH#PBF is available at Aetrix Electronics and suitable for large-screen LCD backlighting, mono/multi-color LED displays, LED billboards and signboards, and automotive exterior lighting requiring stable component supply across extended temperature ranges.
Supply support for LT3746IUHH#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 LT3746 family.
The LT3746IUHH#PBF belongs to Linear's high-performance LED driver product line, designed specifically for demanding display applications requiring precision current matching, high-speed serial control, and robust fault protection.
FAQ
What is the maximum LED forward voltage supported per channel on the LT3746IUHH#PBF?
The LT3746IUHH#PBF supports up to 13V LED forward voltage per channel (LED00–LED31), as specified in Absolute Maximum Ratings. This allows driving 3–4 white LEDs in series (typical VF ≈ 3.2–3.6V) or longer strings of lower-VF red/green LEDs while maintaining safe operation within the 13V pin rating.
Does the LT3746IUHH#PBF require an external buck inductor and MOSFET?
Yes, the LT3746IUHH#PBF requires an external P-channel MOSFET connected to the GATE pin and an external inductor between VIN and ISP/ISN. The IC integrates the buck controller, current sense amplifier, and gate driver-but not passive magnetics or power switches-enabling flexible layout and thermal optimization for high-current designs.
How does the LT3746IUHH#PBF report open or short LED faults?
The LT3746IUHH#PBF monitors each LEDxx pin for voltage thresholds: VOPEN < 0.1V indicates open-circuit; VSHT > 3.65V indicates short-circuit. Detected faults are stored in the 32-bit status register (S0–S31) and transmitted via the serial interface's status frame upon next LDI pulse, enabling real-time system-level diagnostics without polling.
Can the LT3746IUHH#PBF operate without the serial interface enabled?
Yes, the LT3746IUHH#PBF can operate with static LED current settings: all 32 channels default to OFF after Power-on-Reset (POR), but once configured via serial interface, registers retain state until reset. However, dynamic dimming, dot correction, and fault reporting require active serial communication; standalone operation is limited to fixed-current mode with no diagnostics.
What is the purpose of the exposed thermal pad (Pin 57) on the LT3746IUHH#PBF?
The exposed thermal pad (Pin 57) on the LT3746IUHH#PBF is electrically connected to GND and must be soldered to a continuous copper ground plane. It reduces thermal resistance (θJC = 2.0°C/W) to improve power handling, stabilize junction temperature under full 32-channel load, and ensure reliable operation at 125°C junction temperature-critical for outdoor LED signage and automotive applications.
LT3746IUHH#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 56-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Controller
- Topology:
- Step-Down (Buck)
- Internal Switch(s):
- No
- Number of Outputs:
- 32
- Voltage - Supply (Min):
- 6V
- Voltage - Supply (Max):
- 55V
- Voltage - Output:
- -
- Current - Output / Channel:
- 30mA
- Frequency:
- 205Hz ~ 1.05MHz
- Dimming:
- PWM
- Applications:
- Backlight, Signage
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 56-QFN (5x9)
LT3746IUHH#PBF FAQ
1.How can I place an order for LT3746IUHH#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3746IUHH#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 LT3746IUHH#PBF reliable?
The price and inventory of LT3746IUHH#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3746IUHH#PBF is usually 5 days.
3.What payment methods are accepted for LT3746IUHH#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3746IUHH#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3746IUHH#PBF?
LT3746IUHH#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3746IUHH#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 LT3746IUHH#PBF?
For technical support, including LT3746IUHH#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3746IUHH#PBF requirements.
6.How does Aetrix verify that LT3746IUHH#PBF is sourced from the original manufacturer or authorized distributors?
All LT3746IUHH#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 LT3746IUHH#PBF meets industry standards.
7.What is the process for return or replacement of LT3746IUHH#PBF?
All LT3746IUHH#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3746IUHH#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 LT3746IUHH#PBF part is unused and in its original packaging.
Return procedure for LT3746IUHH#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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