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Analog Devices Inc. LT8391AHFE#PBF
- Part No.:
- LT8391AHFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT8391AHFE#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,860
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Product details
Overview
LT8391AHFE#PBF from Analog Devices is a synchronous 4-switch buck-boost LED controller IC designed for automotive and industrial LED driver applications. It regulates LED current across input voltages from 4V to 60V and output voltages from 0V to 60V, supports 600kHz–2MHz switching, delivers ±3% LED current accuracy, and features AEC-Q100 qualification for operation up to 150°C junction temperature.
For engineers reviewing the LT8391AHFE#PBF datasheet, LT8391AHFE#PBF pinout, LT8391AHFE#PBF application, or LT8391AHFE#PBF equivalent, key selection considerations include its 28-lead TSSOP package with exposed pad, peak-buck/peak-boost current mode control, internal/external PWM dimming (128:1 / 2000:1), open/short LED fault reporting, and seamless region transitions between buck, buck-boost, and boost modes.
Technical Context
The LT8391AHFE#PBF implements a proprietary peak-buck/peak-boost current mode architecture that uses a single inductor and dual current sense paths (LSP/LSN for inductor current, ISP/ISN for LED current) to maintain regulation regardless of VIN-to-VOUT relationship. Its control logic dynamically selects buck, buck-boost, or boost topology based on real-time VIN/VOUT ratio, with precise transition thresholds (e.g., buck-boost to boost at VIN/VOUT = 0.75).
It integrates dual gate drivers (TG1/BG1 for buck side; TG2/BG2 for boost side), a 5V INTVCC LDO, 2V VREF reference, and dedicated PWM dimming circuitry including PWMTG high-side PMOS driver. Fault protection includes open/short LED detection via FB and ISP/ISN monitoring, with configurable latch-off, hiccup, or keep-running response via SS pin resistor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 60V - supports wide-input automotive battery systems (cold crank to load dump) and industrial DC supplies without pre-regulation. |
| VOUT Range | 0V to 60V - enables direct drive of multi-LED strings up to 51V forward voltage with no external boost stage. |
| Switching Frequency | 600kHz to 2MHz - adjustable via RT pin; allows EMI optimization and compact magnetics design while maintaining >94% efficiency at 2MHz. |
| LED Current Accuracy | ±3% at 100mV full scale - ensures consistent luminance across temperature and unit-to-unit variation in high-reliability lighting. |
| PWM Dimming Ratio | 2000:1 external, 128:1 internal - enables flicker-free dimming down to 0.05% duty cycle for adaptive lighting and human-centric applications. |
| Junction Temp Range | –40°C to +150°C - qualified per AEC-Q100 Grade H, enabling under-hood placement in automotive headlamp modules. |
| Fault Reporting | Open/short LED detection with FAULT pin - provides system-level diagnostics without requiring external microcontroller polling. |
Pinout & Package
LT8391AHFE#PBF is housed in a 28-lead plastic TSSOP package with exposed 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 proper thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO | Enable & UVLO Input | Enables device above 1.22V threshold; enables programmable undervoltage lockout using resistor divider from VIN. |
| ISP / ISN | LED Current Sense Inputs | Kelvin-connected inputs for high-accuracy LED current regulation; full-scale threshold set by CTRL1/CTRL2 analog voltage. |
| TG1 / BG1 / SW1 / BST1 | Buck-Side Power Switch Drivers | Drive external N-channel MOSFETs in buck configuration; BST1 supplies floating gate drive for top FET. |
| TG2 / BG2 / SW2 / BST2 | Boost-Side Power Switch Drivers | Drive external N-channel MOSFETs in boost configuration; BST2 supplies floating gate drive for top FET. |
| PWMTG | High-Side PMOS PWM Driver | Inverted, buffered PWM output driving external high-side PMOS switch; rail-to-rail swing referenced to VOUT. |
| FAULT | Open-Drain Fault Indicator | Pulled low during open LED (VFB > 0.95V & V(ISP-ISN) < 10mV) or short LED (VFB < 0.25V); requires external pull-up. |
| SS | Soft-Start & Fault Mode Control | Capacitor sets soft-start time; resistor to VREF configures fault response: hiccup (no resistor), latch-off (499kΩ), or keep-running (100kΩ). |
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 space-constrained headlamp designs. |
| Proprietary Peak-Buck/Peak-Boost Control | Ensures continuous conduction and smooth transitions between operating regions without audible noise or current discontinuity. |
| Flicker-Free Spread Spectrum | 25% triangle modulation on SYNC/SPRD = INTVCC reduces peak EMI by >10dB, easing CISPR 25 Class 5 compliance. |
| High-Side PMOS PWM Switch Driver | PWMTG eliminates top-FET refresh noise in buck/boost modes and enables true high-side dimming without floating gate drive complexity. |
| AEC-Q100 Qualified (Grade H) | Validated for automotive use up to 150°C junction temperature; includes production flow, reliability testing, and failure analysis documentation. |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) with matrix LED arrays requiring dynamic beam shaping and dimming. IC Role / Device Role / Timing Role: Primary LED current controller managing multiple independent channels via external PWM and analog dimming inputs. Use Value: Seamless buck/boost/buck-boost transitions prevent beam flicker during vehicle start-stop cycles and battery voltage sag. |
Use Scenario: Warehouse lighting with 48V DC microgrid supply powering 36–48V LED strings. IC Role / Device Role / Timing Role: Constant-current regulator interfacing with DALI or 0–10V control signals via CTRL1/CTRL2 analog inputs. Use Value: Wide 4V–60V input range accepts variable microgrid voltage; ±3% current accuracy ensures uniform lumen output across fixtures. |
| Automotive Daytime Running Lamps (DRL) | Battery-Powered Emergency Lighting |
Use Scenario: Compact DRL module powered directly from 12V vehicle battery with thermal derating for under-hood mounting. IC Role / Device Role / Timing Role: LED driver with integrated thermal foldback (via CTRL2) and fault reporting for ASIL-B–compliant systems. Use Value: CTRL2 input enables linear LED current reduction above 85°C, preventing thermal runaway without firmware intervention. |
Use Scenario: Portable emergency light using 3S Li-ion battery (9–12.6V) driving 24V LED string for extended runtime. IC Role / Device Role / Timing Role: Buck-boost controller maintaining constant LED current as battery discharges below LED forward voltage. Use Value: 94% efficiency at 2MHz enables small inductors and ceramic capacitors, reducing size/weight for portable form factor. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8391AEFE#PBF | Same functionality, but rated for –40°C to +125°C junction temperature; lacks AEC-Q100 qualification. | Suitable for industrial or commercial lighting where automotive reliability certification is not required. | Select LT8391AEFE#PBF when cost sensitivity outweighs automotive qualification needs and ambient temperature remains ≤125°C. |
| LT8390AIFE#PBF | Lower 40V VIN/VOUT rating, no spread spectrum, 1000:1 external PWM dimming, and no PWMTG driver. | Targeted at cost-sensitive non-automotive LED drivers where EMI is less critical and high-side dimming is unnecessary. | Choose LT8390AIFE#PBF only if system requirements fit its narrower voltage range and reduced feature set-no drop-in replacement. |
Compared with LT8391AEFE#PBF, the LT8391AHFE#PBF adds AEC-Q100 qualification and 150°C operation for under-hood use; compared with LT8390AIFE#PBF, it offers higher voltage capability, spread spectrum, and integrated PWMTG-making it uniquely suited for demanding automotive LED systems.
Availability
LT8391AHFE#PBF is available at Aetrix Electronics and suitable for automotive headlamps, 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 LT8391AHFE#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT8391A product line was designed specifically for high-efficiency, high-reliability LED driver applications requiring seamless buck-boost operation, automotive-grade robustness, and advanced dimming control in space- and thermally-constrained environments.
FAQ
What is the maximum operating junction temperature for the LT8391AHFE#PBF?
The LT8391AHFE#PBF is specified for operation up to +150°C junction temperature and is AEC-Q100 qualified for Grade H automotive applications. This rating enables direct mounting in high-temperature locations such as automotive headlamp housings. Thermal derating begins above 125°C, and overtemperature protection activates above 150°C to safeguard the device. Always verify PCB copper area and airflow in final layout to maintain safe thermal margins for LT8391AHFE#PBF.
How does the LT8391AHFE#PBF handle transitions between buck, buck-boost, and boost modes?
The LT8391AHFE#PBF uses a proprietary peak-buck/peak-boost current mode control scheme that continuously monitors VIN/VOUT ratio and switches topology seamlessly without interruption to LED current. Transition thresholds are precisely defined: buck-boost to boost at VIN/VOUT = 0.75, boost to buck-boost at 0.85, buck-boost to buck at 1.25, and buck to buck-boost at 1.33. This eliminates audible noise, current ripple, and light flicker during transient conditions-critical for automotive lighting applications using LT8391AHFE#PBF.
Can the LT8391AHFE#PBF drive a high-side PMOS for PWM dimming without external level-shifting?
Yes-the LT8391AHFE#PBF integrates the PWMTG pin, a dedicated high-side PMOS gate driver with rail-to-rail output swing referenced to VOUT. When enabled, PWMTG provides an inverted, buffered version of the PWM input signal with voltage levels ranging from (VOUT – 5V) to VOUT, eliminating the need for external level shifters or charge pumps. This simplifies high-side dimming implementation and avoids top-FET refresh noise common in buck/boost configurations using LT8391AHFE#PBF.
What fault protection mechanisms does the LT8391AHFE#PBF provide for LED strings?
The LT8391AHFE#PBF provides comprehensive LED fault protection: open LED detection (VFB > 0.95V and V(ISP-ISN) < 10mV), short LED detection (VFB < 0.25V), and overvoltage protection (VFB > 1.05V). All faults trigger the open-drain FAULT pin, which can be configured via SS pin resistor to latch off, enter hiccup mode, or continue operation. These protections are active during PWM high state and latched during low state-ensuring reliable system-level diagnostics in safety-critical applications using LT8391AHFE#PBF.
Is the LT8391AHFE#PBF pin-compatible with other variants in the LT8391A family?
Yes-the LT8391AHFE#PBF shares identical pinout and footprint with all LT8391A variants in the 28-lead TSSOP package (e.g., LT8391AEFE#PBF, LT8391AIFE#PBF). Electrical functionality is identical across grades; only the guaranteed operating junction temperature range and AEC-Q100 qualification differ. This allows direct substitution in existing designs when upgrading to automotive-grade reliability, provided thermal design accommodates the 150°C rating of LT8391AHFE#PBF.
LT8391AHFE#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:
- 600kHz ~ 2MHz
- Dimming:
- Analog, PWM
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
LT8391AHFE#PBF FAQ
1.How can I place an order for LT8391AHFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391AHFE#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 LT8391AHFE#PBF reliable?
The price and inventory of LT8391AHFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391AHFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8391AHFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391AHFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391AHFE#PBF?
LT8391AHFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391AHFE#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 LT8391AHFE#PBF?
For technical support, including LT8391AHFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391AHFE#PBF requirements.
6.How does Aetrix verify that LT8391AHFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8391AHFE#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 LT8391AHFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8391AHFE#PBF?
All LT8391AHFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391AHFE#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 LT8391AHFE#PBF part is unused and in its original packaging.
Return procedure for LT8391AHFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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