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Analog Devices Inc. LT8391AEFE#PBF
- Part No.:
- LT8391AEFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT8391AEFE#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,935
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Product details
Overview
LT8391AEFE#PBF from Analog Devices is a synchronous 4-switch buck-boost LED controller IC that regulates constant LED current across input voltages (4V–60V) above, below, or equal to output (0V–60V), using proprietary peak-buck/peak-boost current mode control at up to 2MHz switching frequency. It delivers ±3% LED current accuracy, supports 2000:1 external PWM dimming, and integrates fault protection for open/short LED conditions - deployed in automotive headlamps and high-frequency industrial LED lighting.
For engineers reviewing the LT8391AEFE#PBF datasheet, LT8391AEFE#PBF pinout, LT8391AEFE#PBF application, or LT8391AEFE#PBF equivalent, key selection criteria include its 28-lead TSSOP package with exposed pad, AEC-Q100 qualification (Grade E, –40°C to +125°C), 60V absolute max VIN/VOUT rating, integrated 5V INTVCC LDO, and dual analog dimming via CTRL1/CTRL2 with thermal derating capability.
Technical Context
The LT8391AEFE#PBF implements a single-inductor, four-MOSFET architecture with independent buck-side (SW1/TG1/BG1/BST1/LSP/LSN) and boost-side (SW2/TG2/BG2/BST2) gate drivers, enabling seamless region transitions (buck → buck-boost → boost) without audible noise or current discontinuity. Its peak-buck/peak-boost current mode control uses a shared ISP/ISN sense path and internal error amplifier (VC output) to regulate LED current while maintaining stable voltage loop feedback via FB (1.00V reference).
Control logic includes synchronized or spread-spectrum (25% triangle) operation via SYNC/SPRD, soft-start timing set by SS capacitor, and fault management through FAULT open-drain output with configurable hiccup/latch-off/keep-running modes. The IC supports both internal PWM dimming (RP-set frequency, 47–97% duty) and external PWM dimming with PWMTG high-side PMOS driver (VOUT-referenced, 2.4V min VOUT for activation).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Synchronous 4-switch buck-boost LED controller - enables single-inductor design with VIN >, <, or = VOUT without topology change. |
| Input Voltage Range | 4V to 60V - supports wide automotive battery transients (4V cold crank to 60V load dump). |
| Output Voltage Range | 0V to 60V - accommodates up to 51V LED string with full regulation and fault detection. |
| Switching Frequency | 600kHz to 2MHz (adjustable via RT resistor) - enables compact magnetics and EMI optimization; 2MHz operation achieves 94% efficiency at 16V/1.5A. |
| LED Current Accuracy | ±3% at 100mV full-scale sense voltage - ensures precise luminance control across temperature and line/load variations. |
| PWM Dimming Ratio | 2000:1 external, 128:1 internal - enables flicker-free dimming down to 0.05% duty cycle with high-resolution brightness control. |
| Operating Temperature | –40°C to +125°C (junction) - qualified per AEC-Q100 Grade E for under-hood automotive LED systems. |
| Package | 28-lead TSSOP with exposed pad - provides low θJA = 30°C/W thermal resistance and GND-connected thermal path. |
Pinout & Package
LT8391AEFE#PBF is housed in a 28-lead plastic TSSOP package (FE) with exposed pad (Pin 29), which must be soldered to PCB ground for thermal and electrical performance. θJA = 30°C/W, θJC = 5°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EN/UVLO | Enable and undervoltage lockout input | Shuts down IC when <0.3V; enables at >1.220V with 13mV hysteresis; supports programmable UVLO with resistor divider from VIN. |
| VIN | Main input supply connection | Accepts 4V–60V input; powers internal 5V INTVCC LDO; requires ≥1µF local ceramic bypass to GND. |
| VOUT | Output supply rail connection | Defines output voltage range (0V–60V); serves as positive rail for PWMTG driver; requires ≥1µF local ceramic bypass. |
| ISP / ISN | High-side LED current sense inputs | Kelvin-connected across RLED; enable ±3% LED current regulation; support open/short LED fault detection via FB monitoring. |
| LSP / LSN | Buck-side inductor current sense inputs | Kelvin-connected across RSENSE; provide inductor current feedback for peak-buck current mode control and reverse current protection. |
| TG1 / BG1 / BST1 / SW1 | Buck-side power switch interface | TG1 drives top N-MOSFET gate (SW1→BST1 swing); BG1 drives bottom N-MOSFET gate (GND→INTVCC); BST1 supplies bootstrap for TG1. |
| TG2 / BG2 / BST2 / SW2 | Boost-side power switch interface | TG2 drives top N-MOSFET gate (SW2→BST2 swing); BG2 drives bottom N-MOSFET gate (GND→INTVCC); BST2 supplies bootstrap for TG2. |
| PWMTG | High-side PMOS PWM switch driver | Inverted buffered PWM output; swings from (VOUT–5V) to VOUT; requires no external level shift for high-side PMOS LED dimming. |
| CTRL1 / CTRL2 | Analog dimming and thermal derating inputs | Set LED current threshold (0–100mV) linearly; CTRL2 supports NTC-based thermal foldback; both tolerate 0.25V–2.0V range. |
| FAULT | Open-drain fault reporting output | Pulled low on open LED (VFB >0.95V & V(ISP-ISN)<10mV) or short LED (VFB <0.25V); latched during PWM low state. |
Key Features
| Feature | Design Value |
|---|---|
| Proprietary peak-buck/peak-boost current mode control | Enables smooth, low-noise transitions between buck, buck-boost, and boost regions without current discontinuity or audible artifacts. |
| 25% triangle spread spectrum modulation | Reduces EMI peak emissions by spreading switching energy across 21–25% bandwidth above base frequency - meets CISPR 25 Class 5. |
| Integrated 5V INTVCC LDO with 145mA current limit | Powers internal circuitry and gate drivers directly from VIN; eliminates need for external bias supply; supports 0–80mA load with ≤4% regulation error. |
| Configurable fault response (hiccup/latch-off/keep-running) | Set via single resistor from SS to VREF (499kΩ = latch-off, 100kΩ = keep-running, no resistor = hiccup) - enables system-level fault strategy alignment. |
| High-side PMOS PWM driver (PWMTG) | Eliminates need for external level shifter; drives PMOS gate referenced to VOUT; activates only when VOUT ≥2.4V - prevents false turn-on during startup. |
| AEC-Q100 Grade E qualification | Validated for automotive applications including headlamps and DRLs; supports extended temperature operation (–40°C to +125°C junction). |
Applications
| Automotive Headlamp Systems | Industrial High-Bay LED Lighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) requiring dynamic beam shaping and high-luminance output across 8–16V battery range with transient immunity. IC Role / Device Role / Timing Role: Primary LED current controller managing 4-switch buck-boost topology to maintain constant 1.5A current into 40V LED string despite VIN fluctuations from 6V (cold crank) to 32V (load dump). Use Value: Seamless region transition avoids light flicker during engine start/stop; ±3% current accuracy ensures consistent photometric output; AEC-Q100 qualification guarantees reliability in under-hood environments. |
Use Scenario: Factory-floor high-bay fixture operating from 24VDC industrial bus with 50V LED string, requiring high efficiency and thermal robustness in ambient up to 70°C. IC Role / Device Role / Timing Role: Constant-current LED driver implementing 2MHz switching to minimize inductor size and reduce EMI coupling into adjacent PLC and sensor circuits. Use Value: 94% efficiency at 2MHz reduces thermal load on heatsink; CTRL2 thermal derating protects LEDs at elevated ambient; 60V VOUT rating supports future higher-Vf LED upgrades. |
| Aviation Cabin Lighting | Emergency Exit Signage |
Use Scenario: FAA-certified cabin lighting module powered from 28VDC aircraft bus, needing ultra-low EMI and flicker-free dimming across 0.1–100% range. IC Role / Device Role / Timing Role: LED controller executing spread-spectrum switching and 2000:1 external PWM dimming to eliminate visible beat frequencies with camera systems and human vision. Use Value: Triangle SS modulation suppresses narrowband EMI peaks critical for avionics compliance; PWMTG driver enables direct high-side PMOS dimming without floating gate drive complexity. |
Use Scenario: UL 924-compliant emergency egress signage with red LED strings, requiring fail-safe open/short LED detection and continuous operation during AC loss. IC Role / Device Role / Timing Role: Fault-aware LED driver using FAULT pin reporting and SS-configured keep-running mode to sustain illumination even during partial LED string failure. Use Value: Real-time open/short LED detection via ISP/ISN + FB correlation ensures immediate fault visibility; latch-off/hiccup options support different safety architectures per certification body. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EFE#PBF | 4-switch buck-boost controller with 4V–36V input, no integrated PWM dimming driver, lower max VOUT (36V), no SS modulation. | Targeted at general DC/DC conversion; lacks dedicated LED features (ISP/ISN, PWMTG, fault reporting). | Select when primary need is wide-input DC/DC regulation without LED-specific functions or automotive qualification. |
| LT3762EFE#PBF | Boost-only LED controller with 4V–40V input, 0V–60V output, integrated PWM dimming, but no buck-boost capability or region transition. | Optimized for boost-only LED strings where VIN always < VOUT; no support for input above output. | Select for cost-sensitive boost-only designs where input never exceeds LED string voltage and AEC-Q100 is not required. |
Compared with LTC3789EFE#PBF and LT3762EFE#PBF, the LT8391AEFE#PBF uniquely combines 4-switch buck-boost topology, AEC-Q100 Grade E qualification, integrated PWMTG driver, and spread-spectrum EMI reduction - making it the only option supporting automotive adaptive lighting with full VIN/VOUT overlap and certified reliability.
Availability
LT8391AEFE#PBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and aviation cabin systems requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant performance.
Supply support for LT8391AEFE#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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision, power, and connectivity applications.
The LT8391A product line is designed specifically for high-efficiency, high-reliability LED driver applications demanding wide input/output voltage range, seamless topology transitions, and automotive-grade robustness - targeting adaptive lighting and mission-critical illumination systems.
FAQ
What is the maximum input voltage rating for the LT8391AEFE#PBF?
The LT8391AEFE#PBF has an absolute maximum input voltage rating of 60V on the VIN pin, with continuous operation supported from 4V to 60V. Transient tolerance extends to 56V for automotive load-dump conditions, and the device maintains regulation and fault protection across this full range. This rating is confirmed in the Absolute Maximum Ratings table and validated in the Electrical Characteristics section under VIN Operating Voltage Range.
Does the LT8391AEFE#PBF support spread-spectrum frequency modulation?
Yes, the LT8391AEFE#PBF supports triangle spread-spectrum modulation with a 25% frequency deviation above the base oscillator frequency when the SYNC/SPRD pin is tied to INTVCC. This feature is explicitly documented in the FEATURES list and Electrical Characteristics table under "Highest Spread Spectrum Above Oscillator Frequency", reducing EMI peak emissions without compromising regulation stability.
How does the LT8391AEFE#PBF handle LED open-circuit faults?
The LT8391AEFE#PBF detects open LED faults by monitoring both FB voltage (>0.95V) and ISP–ISN differential voltage (<10mV). When both conditions occur simultaneously, the FAULT pin is pulled low. Fault response mode (hiccup, latch-off, or keep-running) is configured via a resistor from SS to VREF. This dual-threshold detection method is specified in the Electrical Characteristics table under "FB Open LED Threshold" and "ISP/ISN Open LED Threshold".
What package type and thermal characteristics does the LT8391AEFE#PBF use?
The LT8391AEFE#PBF uses a 28-lead plastic TSSOP package (FE) with exposed pad (Pin 29), which must be soldered to PCB ground. Its thermal metrics are θJA = 30°C/W and θJC = 5°C/W, as stated in the Pin Configuration diagram. This package supports AEC-Q100 Grade E operation (–40°C to +125°C junction) and enables efficient heat dissipation in space-constrained automotive and industrial LED modules.
Can the LT8391AEFE#PBF drive a high-side PMOS for PWM dimming without external level shifting?
Yes, the LT8391AEFE#PBF integrates the PWMTG pin - a buffered, inverted PWM output referenced to VOUT - enabling direct drive of high-side PMOS switches without external level shifters. PWMTG activates only when VOUT ≥2.4V and swings from (VOUT–5V) to VOUT, as verified in the Electrical Characteristics table under "Minimum VOUT for PWMTG to be On" and "PWMTG On Voltage".
LT8391AEFE#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 ~ 125°C (TJ)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
LT8391AEFE#PBF FAQ
1.How can I place an order for LT8391AEFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391AEFE#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 LT8391AEFE#PBF reliable?
The price and inventory of LT8391AEFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391AEFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8391AEFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391AEFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391AEFE#PBF?
LT8391AEFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391AEFE#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 LT8391AEFE#PBF?
For technical support, including LT8391AEFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391AEFE#PBF requirements.
6.How does Aetrix verify that LT8391AEFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8391AEFE#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 LT8391AEFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8391AEFE#PBF?
All LT8391AEFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391AEFE#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 LT8391AEFE#PBF part is unused and in its original packaging.
Return procedure for LT8391AEFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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