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Analog Devices Inc. LT8391IFE#PBF
- Part No.:
- LT8391IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT8391IFE#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,860
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Product details
Overview
LT8391IFE#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 sense voltage, supports 150kHz–650kHz adjustable switching frequency, and integrates bootstrap diodes for simplified gate drive in automotive headlamp and high-power LED lighting systems.
For engineers reviewing the LT8391IFE#PBF datasheet, LT8391IFE#PBF pinout, LT8391IFE#PBF application, or LT8391IFE#PBF equivalent, key selection considerations include its seamless buck/buck-boost/boost region transitions, internal/external PWM dimming (128:1 / 2000:1), AEC-Q100 qualification, fault reporting via open/short LED detection, and TSSOP-28 package with exposed thermal pad.
Technical Context
The LT8391IFE#PBF implements a dual-mode current-sense architecture: LSP/LSN monitors inductor current for peak-buck (buck region) and peak-boost (boost region) control, while ISP/ISN senses LED current for regulation and fault detection. Its control logic dynamically selects operating region based on VIN/VOUT ratio-transition thresholds are precisely defined (e.g., buck-to-buck-boost at VIN/VOUT = 1.16–1.20, peak-buck-to-peak-boost at 0.96–1.00).
It features two independent analog dimming inputs (CTRL1/CTRL2) enabling 20:1 linear dimming with ±3% LED current accuracy at full scale, plus integrated soft-start (SS pin), spread spectrum (SYNC/SPRD tied to INTVCC), and fault management modes (hiccup/latch-off/keep-running) selectable via SS-to-VREF resistor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide automotive battery transients and industrial DC rails without pre-regulation. |
| Output Voltage Range | 0V to 60V - enables direct connection to LED strings up to 51V forward voltage with no external boost stage. |
| LED Current Accuracy | ±3% at 100mV full-scale sense voltage - ensures consistent luminance across temperature and unit variation. |
| Switching Frequency | 150kHz to 650kHz (adjustable via RT resistor) - allows EMI optimization and inductor size trade-offs. |
| PWM Dimming Ratio | 2000:1 external, 128:1 internal - supports flicker-free dimming down to 0.05% duty cycle for architectural and automotive lighting. |
| Analog Dimming Range | 20:1 via CTRL1/CTRL2 - provides smooth, noise-free brightness control without PWM artifacts. |
| Operating Temperature | –40°C to +125°C junction - qualified for under-hood automotive and industrial ambient environments. |
| AEC-Q100 Grade | Grade I - certified for automotive applications including headlamps and DRLs per stress test requirements. |
Pinout & Package
LT8391IFE#PBF is housed in a 28-lead plastic TSSOP package with exposed thermal pad (Pin 29 = GND), optimized for thermal dissipation in high-power LED driver PCB layouts. The exposed pad must be soldered directly to the PCB ground plane for reliable operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO | Enable and input undervoltage lockout | Shuts down IC when <0.3V; enables at >1.214V with 13mV hysteresis - enables programmable VIN UVLO using resistor divider. |
| VIN | Main input supply rail | Power source for internal LDO (INTVCC) and gate drivers; requires ≥1µF local ceramic bypass to GND. |
| VOUT | Output supply rail | Determines boost-side operating point; serves as positive rail for PWMTG driver; requires ≥1µF local ceramic bypass. |
| ISP/ISN | High-side LED current sense terminals | Kelvin-connected inputs for precise LED current regulation and open/short fault detection (thresholds: 10mV open, 750mV overcurrent). |
| LSP/LSN | Buck-side inductor current sense terminals | Kelvin-connected inputs for peak-buck/peak-boost current mode control and reverse current protection (±4mV reverse threshold). |
| TG1/BG1/TG2/BG2 | N-channel MOSFET gate drivers | Four independent gate drivers with 2.6Ω pull-up / 1.4Ω pull-down (TG), 3.2Ω/1.2Ω (BG); support synchronous 4-switch topology. |
| BST1/BST2 | Bootstrap supply pins | Integrated Schottky diodes from INTVCC feed external bootstrap capacitors - eliminate external diodes and simplify layout. |
| PWMTG | High-side PMOS PWM switch driver | Inverted buffered PWM output swinging from (VOUT –5V) to VOUT - drives external high-side PMOS for true high-side dimming. |
| CTRL1/CTRL2 | Analog dimming and thermal derating inputs | Accept 0.25V–2V analog voltage; enable 20:1 dimming (CTRL1) and temperature-dependent current derating (CTRL2). |
| FAULT | Open-drain fault reporting output | Pulled low during open LED (VFB >0.95V & V(ISP-ISN)<10mV) or short LED (VFB <0.25V); updated only during PWM high state. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor architecture | Enables seamless VIN-above/VOUT, VIN-below/VOUT, and VIN-near-VOUT operation without topology reconfiguration or efficiency cliffs. |
| Proprietary peak-buck/peak-boost current mode | Eliminates discontinuous conduction mode (DCM) gaps and reduces audible noise during region transitions. |
| Flicker-free spread spectrum | ±15% triangle modulation around oscillator frequency (via SYNC/SPRD = INTVCC) lowers peak EMI by >10dB without affecting regulation. |
| Integrated bootstrap diodes | Removes two external Schottky diodes per side - reduces BOM count, layout area, and potential failure points in high-reliability designs. |
| No top MOSFET refresh noise | Eliminates gate-drive coupling spikes during buck/boost transitions - critical for low-noise LED current regulation and EMC compliance. |
| Three fault response modes | Selectable via SS-to-VREF resistor: hiccup (no resistor), latch-off (499kΩ), or keep-running (100kΩ) - enables system-level fault strategy alignment. |
Applications
| Automotive Headlamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) requiring dynamic beam shaping and wide dimming range across 9–16V battery input with 48V LED arrays. IC Role / Device Role / Timing Role: Primary LED current controller managing 4-switch buck-boost conversion, real-time region transition, and synchronized PWM dimming for pixel-level control. Use Value: Delivers 98% peak efficiency at 25V/2A while maintaining ±3% current accuracy across –40°C to +125°C - ensures consistent photometric output and AEC-Q100 compliance. |
Use Scenario: 100W+ warehouse lighting using multi-string 36V LEDs powered from 24–60V DC microgrids or PoE++ infrastructure. IC Role / Device Role / Timing Role: Constant-current LED driver with analog dimming interface for DALI-2 or 0–10V control systems and robust open/short LED fault handling. Use Value: Supports 2000:1 external PWM dimming and 20:1 analog dimming without color shift - meets IEEE 1789 flicker mitigation guidelines for human-centric lighting. |
| Battery-Powered Emergency Lighting | UV-C Disinfection Systems |
Use Scenario: Portable emergency egress lighting using Li-ion (3.0–4.2V/cell) or lead-acid (12–14.4V) batteries driving 24–48V LED strings. IC Role / Device Role / Timing Role: Wide-input buck-boost LED controller enabling single-stage regulation from depleted to fully charged battery states. Use Value: 4V minimum VIN operation extends runtime; ±3% current accuracy maintains uniform light output across battery discharge curve. |
Use Scenario: Pulsed UV-C LED arrays (275nm, 3.5–4.5V VF) requiring precise current control and thermal derating for germicidal efficacy and LED lifetime. IC Role / Device Role / Timing Role: High-accuracy current regulator with CTRL2-based thermal feedback loop to reduce drive current above 60°C. Use Value: Enables 100% rated current at ≤60°C and linear derating to zero at 125°C - prevents UV-C output degradation and catastrophic LED failure. |
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 with I²C interface, 12-bit dimming resolution, and built-in fault diagnostics; operates up to 60V but lacks spread spectrum and has narrower analog dimming (10:1). | Best suited for digitally controlled smart lighting where I²C configuration and telemetry are required; not AEC-Q100 qualified. | Choose LT3965EFE#PBF when digital configurability and fault logging outweigh need for analog simplicity and automotive qualification. |
| LM34927QMH/NOPB | Automotive-grade 4-switch buck-boost controller with 500kHz max frequency, no integrated bootstrap diodes, and only 1000:1 external PWM dimming; lacks CTRL2 thermal derating and spread spectrum. | Targeted at cost-sensitive automotive lighting with lower performance requirements; requires external bootstrap diodes and offers less EMI control. | Choose LM34927QMH/NOPB for entry-level automotive applications where BOM cost is prioritized over EMI performance and thermal intelligence. |
Compared with LT3965EFE#PBF and LM34927QMH/NOPB, the LT8391IFE#PBF uniquely combines AEC-Q100 Grade I qualification, ±15% spread spectrum, integrated bootstrap diodes, and dual analog dimming/thermal inputs - making it optimal for high-reliability, low-EMI, thermally adaptive LED systems where analog control and automotive compliance are mandatory.
Availability
LT8391IFE#PBF is available at Aetrix Electronics and suitable for automotive headlamp design, industrial high-bay lighting, and battery-powered emergency lighting requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.
Supply support for LT8391IFE#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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision signal chain and power management applications.
The LT8391 product line is designed specifically for high-efficiency, wide-input-range LED current regulation in demanding environments - emphasizing seamless topology transitions, automotive reliability, and flicker-free dimming for advanced lighting systems.
FAQ
What is the maximum LED string voltage supported by the LT8391IFE#PBF?
The LT8391IFE#PBF supports an output voltage range of 0V to 60V, with datasheet validation up to 51V LED forward voltage in typical applications. Its VOUT pin rating is 60V absolute maximum, enabling direct drive of multi-series LED strings without external voltage boosting stages. Operation remains stable across the full range with seamless buck/buck-boost/boost transitions.
Does the LT8391IFE#PBF require external bootstrap diodes?
No, the LT8391IFE#PBF integrates Schottky bootstrap diodes from the INTVCC pin to both BST1 and BST2 pins, eliminating the need for external diodes. This reduces BOM count, PCB area, and potential failure mechanisms - confirmed in the Pin Functions section and Absolute Maximum Ratings table of the official datasheet.
How does the LT8391IFE#PBF handle LED open-circuit faults?
The LT8391IFE#PBF detects open LED conditions when FB voltage exceeds 0.95V *and* ISP–ISN voltage falls below 10mV. Upon detection, it pulls the FAULT pin low and enters a user-selectable response mode (hiccup, latch-off, or keep-running) configured via the SS-to-VREF resistor. Fault status is latched during PWM low time and updated only during PWM high time.
Can the LT8391IFE#PBF operate with input voltage below 4V?
No - the LT8391IFE#PBF has a specified minimum input voltage of 4V per the Electrical Characteristics table. Below this threshold, internal circuitry (including INTVCC LDO and gate drivers) cannot maintain regulation or safe switching. Attempting operation below 4V may result in undefined behavior or failure to start.
What thermal grade does the LT8391IFE#PBF support?
The LT8391IFE#PBF is rated for an operating junction temperature range of –40°C to +125°C, corresponding to Industrial Grade (I-grade) per Analog Devices' ordering nomenclature. This is explicitly stated in the ORDER INFORMATION table and confirmed in the Absolute Maximum Ratings section of the datasheet.
LT8391IFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) 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-TSSOP-EP
LT8391IFE#PBF FAQ
1.How can I place an order for LT8391IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391IFE#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 LT8391IFE#PBF reliable?
The price and inventory of LT8391IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391IFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8391IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391IFE#PBF?
LT8391IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391IFE#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 LT8391IFE#PBF?
For technical support, including LT8391IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391IFE#PBF requirements.
6.How does Aetrix verify that LT8391IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8391IFE#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 LT8391IFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8391IFE#PBF?
All LT8391IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391IFE#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 LT8391IFE#PBF part is unused and in its original packaging.
Return procedure for LT8391IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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