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Analog Devices Inc. LT8391IUFD#PBF
- Part No.:
- LT8391IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT8391IUFD#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:238
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Product details
Overview
LT8391IUFD#PBF from Analog Devices is a synchronous 4-switch buck-boost LED controller that regulates constant LED current across input voltages (4V–60V) both above, below, or equal to output voltage (0V–60V), using proprietary peak-buck/peak-boost current mode control. It delivers ±3% LED current accuracy at 100mV full scale, supports 2000:1 external PWM dimming, and integrates bootstrap diodes for simplified high-side NMOS gate drive in automotive headlamp and industrial high-power LED lighting systems.
For engineers reviewing the LT8391IUFD#PBF datasheet, LT8391IUFD#PBF pinout, LT8391IUFD#PBF application, or LT8391IUFD#PBF equivalent, key selection criteria include its 4V–60V input range, seamless buck/buck-boost/boost region transitions, ±15% triangle spread spectrum for EMI reduction, AEC-Q100 qualification, and 28-lead 4mm × 5mm QFN package with exposed thermal pad.
Technical Context
The LT8391IUFD#PBF implements a proprietary dual-mode current sensing architecture: it monitors inductor current via LSP/LSN in all operating regions and uses ISP/ISN for precise LED current regulation. Its peak-buck/peak-boost control logic dynamically adjusts switching node duty cycles-TG1/BG1 in buck, TG2/BG2 in boost, and fixed 85%/15% duty pairing in buck-boost-to maintain continuous conduction and low-noise transitions at VIN/VOUT ratios of 0.75, 0.85, 1.18, and 1.33.
It integrates two independent gate drivers (TG1/BG1 and TG2/BG2) with 2.6Ω pull-up / 1.4Ω pull-down on NMOS outputs and 3.2Ω/1.2Ω on PMOS-compatible bottom gates, plus a dedicated PWMTG output driving external high-side PMOS switches with rail-to-rail swing referenced to VOUT. Internal 5V INTVCC and 2V VREF regulators supply bias with ±1% line/load regulation over temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - enables direct integration into 12V/24V/48V automotive and industrial battery systems without pre-regulation. |
| Output Voltage Range | 0V to 60V - supports single-string to multi-string LED arrays up to 51V forward voltage with no external op-amp feedback compensation. |
| LED Current Accuracy | ±3% at 100mV full scale - ensures consistent luminance across temperature and unit-to-unit variation in high-reliability lighting. |
| Dimming Ratio | 2000:1 external PWM - achieves flicker-free dimming down to 0.05% duty cycle using standard microcontroller GPIO signals. |
| Switching Frequency | 150kHz to 650kHz adjustable via RT resistor - allows optimization of magnetics size vs. EMI performance; ±15% triangle spread spectrum reduces peak radiated emissions. |
| Operating Temp Range | –40°C to +125°C junction - qualified for under-hood automotive applications and industrial environments with extended thermal cycling. |
| Fault Protection | Open LED (VFB > 0.95V & V(ISP-ISN) < 10mV), short LED (VFB < 0.25V), and thermal shutdown - provides latch-off, hiccup, or keep-running modes configurable via SS pin resistor. |
Pinout & Package
LT8391IUFD#PBF is housed in a 28-lead (4mm × 5mm) plastic QFN package with exposed thermal pad (Pin 29 = GND), θJA = 43°C/W, θJC = 3.4°C/W. The exposed pad must be soldered to PCB ground for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ISP / ISN | LED current sense differential inputs | Kelvin-connected to RLED for ±3% LED current regulation accuracy; common-mode range 0V–60V supports high-side or low-side sensing. |
| LSP / LSN | Inductor current sense differential inputs | Monitor single inductor current in all regions (buck/boost/buck-boost); enable seamless transitions without discontinuity or audible noise. |
| TG1 / BG1 / TG2 / BG2 | NMOS gate drivers | Drive external N-channel MOSFETs in 4-switch topology; integrated bootstrap diodes eliminate external Schottky diodes on BST1/BST2. |
| PWMTG | Inverted PWM top-gate driver | Drives external high-side PMOS switch with rail-to-rail swing (VOUT – 5V to VOUT); eliminates need for level-shifting circuitry. |
| CTRL1 / CTRL2 | Analog dimming and thermal derating inputs | Enable 20:1 analog dimming (±3% accuracy) and programmable LED current derating vs. temperature using negative-coefficient thermistor networks. |
| SYNC/SPRD | Frequency control terminal | Ground for fixed frequency, INTVCC for ±15% triangle spread spectrum, or external clock for synchronization to system timing reference. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor architecture | Eliminates need for separate buck and boost converters; reduces BOM count, board area, and EMI sources in wide-input LED drivers. |
| Proprietary peak-buck/peak-boost control | Ensures continuous conduction and smooth transitions between operating regions without current discontinuity or audible artifacts. |
| Integrated bootstrap diodes | Removes requirement for external Schottky diodes on BST1/BST2 pins, simplifying layout and improving reliability in high-vibration environments. |
| AEC-Q100 Grade I qualification | Validated for automotive applications including headlamps and DRLs, with guaranteed operation from –40°C to +125°C junction temperature. |
| Flicker-free spread spectrum | Triangle modulation spreads energy across 12.5–14.5% above and –13.7––15.7% below oscillator frequency, reducing peak EMI by >10dB. |
| Configurable fault response | SS pin resistor selects open/short LED protection behavior: 499kΩ = latch-off, 100kΩ = keep-running, no resistor = hiccup mode. |
Applications
| Automotive Head Lamps | Industrial High-Power Lighting |
|---|---|
Use Scenario: Adaptive front-lighting systems (AFS) requiring dynamic beam shaping and high-luminance output across 9–16V battery range with cold-cranking support down to 4V. IC Role / Device Role / Timing Role: Primary LED current controller managing 25V/2A (50W) buck-boost output with seamless transition between low-beam (buck), adaptive cornering (buck-boost), and high-beam (boost) modes. Use Value: Enables single-stage architecture replacing dual-converter solutions, reducing system cost by 22% and PCB area by 35% while maintaining <1% current ripple. | Use Scenario: Factory floor high-bay LED fixtures powered from 24V or 48V DC distribution rails, requiring stable 40V/1.5A output despite input sag during motor startup. IC Role / Device Role / Timing Role: Constant-current LED driver supporting 0–10V analog dimming and DALI-compatible PWM dimming with 2000:1 ratio and zero-flicker operation. Use Value: Delivers 98% peak efficiency at 50W, reducing thermal load on heatsinks and enabling fanless enclosure designs for IP66-rated luminaires. |
| Battery-Powered Emergency Lighting | UV-C LED Disinfection Systems |
Use Scenario: Portable emergency egress lighting using Li-ion packs (10–26V) driving 36V LED strings, requiring ultra-low quiescent current during standby and fast wake-up. IC Role / Device Role / Timing Role: Buck-boost LED controller with 1µA VIN shutdown current and EN/UVLO hysteresis programmable via resistor divider for precise brown-out detection. Use Value: Extends battery runtime by 40% versus discrete solutions due to sub-2µA shutdown IQ and integrated 5V regulator eliminating external LDO. | Use Scenario: Pulsed UV-C disinfection modules using 275nm LEDs with strict current stability requirements (<±2%) to ensure germicidal dose consistency across varying input voltage and temperature. IC Role / Device Role / Timing Role: Precision LED current controller with ±3% accuracy, thermal derating via CTRL2, and open/short LED fault reporting for safety-critical validation. Use Value: Guarantees repeatable 30mJ/cm² UV dose per pulse by maintaining LED current within specification across –20°C to +70°C ambient. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3965EFE#PBF | 4-switch buck-boost LED controller in 28-lead TSSOP; lacks spread spectrum, lower max VIN (55V), no PWMTG output | Targeted at non-automotive industrial lighting where EMI is less constrained and high-side PMOS drive is not required | Select when footprint compatibility with TSSOP is needed and spread spectrum is unnecessary; verify thermal design for same power level. |
| LM3423MH/NOPB | Asynchronous boost-only LED controller; no buck capability, no integrated gate drivers, requires external high-side switch | Suitable only for fixed-VIN < VOUT applications like 12V-to-48V LED strings; no region transition support | Choose only if input always remains below output; expect higher component count, lower efficiency (~92%), and no AEC-Q100 qualification. |
Compared with LT3965EFE#PBF and LM3423MH/NOPB, the LT8391IUFD#PBF uniquely combines 4-switch architecture, ±15% spread spectrum, integrated PWMTG, and AEC-Q100 qualification-making it the only option for automotive-grade, wide-input-range, low-EMI LED drivers requiring single-inductor simplicity.
Availability
LT8391IUFD#PBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-power lighting, battery-powered emergency lighting, and UV-C disinfection systems requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.
Supply support for LT8391IUFD#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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT8391 product line delivers high-efficiency, wide-input-range LED controllers optimized for automotive lighting and industrial solid-state illumination, emphasizing seamless region transitions, low EMI, and robust fault handling in harsh environments.
FAQ
What is the maximum LED string voltage supported by the LT8391IUFD#PBF?
The LT8391IUFD#PBF supports an output voltage range of 0V to 60V, with datasheet validation up to 51V LED forward voltage in typical applications. Its internal fault protection thresholds (e.g., FB open LED at 0.95V) and ISP/ISN common-mode range (0V–60V) confirm safe operation at full 60V VOUT, provided external MOSFETs and passive components are rated accordingly. The LT8391IUFD#PBF does not regulate voltage directly but maintains constant current regardless of VOUT within this range.
How does the LT8391IUFD#PBF handle transitions between buck, buck-boost, and boost modes?
The LT8391IUFD#PBF uses proprietary peak-buck/peak-boost current mode control with defined VIN/VOUT transition thresholds: buck-to-buck-boost at 1.18, buck-boost-to-boost at 0.85, and peak-buck-to-peak-boost at 1.00. These ratios trigger automatic reconfiguration of gate drive timing-shifting from TG1/BG1 dominance to TG2/BG2 pairing-ensuring continuous inductor current and low-noise operation without user intervention. The LT8391IUFD#PBF achieves this using a single LSP/LSN current sense resistor and internal logic that detects region boundaries in real time.
Can the LT8391IUFD#PBF drive high-side PMOS switches without external level shifters?
Yes-the LT8391IUFD#PBF includes a dedicated PWMTG pin that provides an inverted, buffered PWM signal with rail-to-rail swing referenced to VOUT (from VOUT–5V to VOUT). This eliminates the need for external level-shifting circuitry when driving high-side PMOS dimming switches. The PWMTG output is designed to interface directly with PMOS gates, and its 10ns rise/fall times and 90ns/40ns propagation delays ensure precise timing alignment with the main switching waveform. The LT8391IUFD#PBF datasheet specifies minimum VOUT for PWMTG activation as 2.4V.
What fault protection modes are configurable on the LT8391IUFD#PBF, and how are they set?
The LT8391IUFD#PBF supports three open/short LED fault responses-hiccup, latch-off, and keep-running-selected by connecting a resistor from the SS pin to VREF. A 499kΩ resistor configures latch-off (FAULT remains asserted until reset), 100kΩ enables keep-running (continues switching during fault), and no resistor defaults to hiccup mode (repeated start attempts). These modes are confirmed in the Applications Information section of the LT8391IUFD#PBF datasheet and do not require firmware or external logic. The FAULT pin reports status as an open-drain output pulled low during active faults.
Is the LT8391IUFD#PBF pin-compatible with other variants in the LT8391 family?
Yes-the LT8391IUFD#PBF shares identical pinout and footprint with all UFD-package variants (LT8391EUFD#PBF, LT8391JUFD#PBF, LT8391HUFD#PBF) and is functionally compatible with FE-package TSSOP versions (e.g., LT8391IFE#PBF) except for thermal pad configuration and θJA. All LT8391 variants use the same 28-pin assignment across packages, and the LT8391IUFD#PBF's –40°C to +125°C operating range matches the I-grade specification. No PCB redesign is needed when migrating between UFD-package grades.
LT8391IUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Controller
- Topology:
- Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- No
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 4V
- Voltage - Supply (Max):
- 60V
- Voltage - Output:
- 60V
- Current - Output / Channel:
- -
- Frequency:
- 150kHz ~ 650kHz
- Dimming:
- Analog, PWM
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LT8391IUFD#PBF FAQ
1.How can I place an order for LT8391IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391IUFD#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 LT8391IUFD#PBF reliable?
The price and inventory of LT8391IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LT8391IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391IUFD#PBF?
LT8391IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391IUFD#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 LT8391IUFD#PBF?
For technical support, including LT8391IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391IUFD#PBF requirements.
6.How does Aetrix verify that LT8391IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LT8391IUFD#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 LT8391IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LT8391IUFD#PBF?
All LT8391IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391IUFD#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 LT8391IUFD#PBF part is unused and in its original packaging.
Return procedure for LT8391IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT8391IUFD#PBF Tags
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