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Analog Devices Inc. LT8391AIUFD#PBF
- Part No.:
- LT8391AIUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT8391AIUFD#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:110
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Product details
Overview
LT8391AIUFD#PBF from Analog Devices is a synchronous 4-switch buck-boost LED controller IC designed for high-frequency, wide-input/output LED driver applications. It operates from 4V to 60V input and delivers 0V to 60V output with ±3% LED current accuracy, 20:1 analog dimming via two CTRL pins, and 2MHz fixed-frequency switching-enabling compact, low-EMI automotive headlamp and industrial lighting designs.
For engineers reviewing the LT8391AIUFD#PBF datasheet, LT8391AIUFD#PBF pinout, LT8391AIUFD#PBF application, or LT8391AIUFD#PBF equivalent, key selection considerations include its 28-pin QFN (4mm × 5mm) package, AEC-Q100 qualification, seamless buck/buck-boost/boost region transitions, integrated 5V INTVCC regulator, and dual PWM/analog dimming architecture supporting up to 2000:1 external PWM dimming ratio.
Technical Context
The LT8391AIUFD#PBF implements Analog Devices' proprietary peak-buck/peak-boost current mode control using a single inductor and shared ISP/ISN current sense path. It dynamically selects operating region (buck, buck-boost, or boost) based on VIN/VOUT ratio-transitioning at precisely defined thresholds (e.g., buck-to-buck-boost at VIN/VOUT = 1.25) without audible noise or regulation discontinuity.
Its gate drivers support NMOS high-side (TG1/TG2) and NMOS low-side (BG1/BG2) switches with 2.6Ω pull-up / 1.4Ω pull-down resistance, while the PWMTG output drives an external high-side PMOS for flicker-free LED dimming. Spread spectrum operation (25% triangle modulation) is enabled by tying SYNC/SPRD to INTVCC.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Synchronous 4-switch buck-boost - enables single-inductor operation across VIN < VOUT, VIN > VOUT, and VIN ≈ VOUT without topology change or efficiency penalty. |
| Input Voltage Range | 4V to 60V - supports 12V/24V/48V automotive and industrial rails, including cold-crank (4V) and load-dump (60V) transients. |
| Output Voltage Range | 0V to 60V - accommodates LED strings up to 51V forward voltage with full regulation and fault protection. |
| Switching Frequency | 600kHz to 2MHz (adjustable via RT pin) - enables use of small 2.2µH inductors and ceramic output capacitors for high-density layouts. |
| LED Current Accuracy | ±3% at 100mV full-scale sense voltage - ensures consistent luminance across temperature and unit-to-unit variation in production systems. |
| Dimming Support | 20:1 analog (via CTRL1/CTRL2), 128:1 internal PWM, 2000:1 external PWM - provides flicker-free brightness control from 0.05% to 100% without color shift. |
| Operating Temperature | –40°C to +125°C junction - qualified per AEC-Q100 Grade I, suitable for under-hood automotive and harsh industrial environments. |
Pinout & Package
LT8391AIUFD#PBF is housed in a 28-lead plastic QFN package (4mm × 5mm) with exposed thermal pad (Pin 29 = GND). The package features θJA = 43°C/W and θJC = 3.4°C/W, requiring PCB-level thermal management via soldered exposed pad.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ISP / ISN | LED current sense differential inputs | Kelvin-connected to RLED; enable precise ±3% LED current regulation independent of trace resistance or layout asymmetry. |
| CTRL1 / CTRL2 | Analog dimming and thermal derating inputs | Program LED current threshold linearly (0–100mV) or set fixed 100mV full scale; CTRL2 accepts NTC divider for automatic thermal current roll-off. |
| PWM / PWMTG | External PWM dimming interface and high-side PMOS gate driver | PWM accepts 0–5V logic signal; PWMTG delivers inverted, buffered output (VOUT–5V to VOUT) to drive external PMOS switch with minimal refresh noise. |
| TG1 / BG1 / TG2 / BG2 | NMOS gate drivers (buck/boost sides) | Drive external N-channel MOSFETs with rail-to-rail swing; TG1/TG2 referenced to SW1/SW2, BG1/BG2 referenced to GND - enables efficient 4-switch implementation. |
| FB / VC / SS | Voltage loop feedback, error amplifier output, soft-start timing | FB regulates VOUT to 1.00V for open/short LED detection; VC sets current comparator threshold; SS capacitor controls startup ramp rate and fault latch behavior. |
Key Features
| Feature | Design Value |
|---|---|
| Proprietary peak-buck/peak-boost control | Eliminates discontinuous conduction mode (DCM) gaps and audible switching artifacts during region transitions - critical for automotive lighting compliance. |
| Integrated 5V INTVCC LDO | Supplies internal circuitry and gate drivers from VIN; 145mA current limit and <160mV dropout at 20mA enable stable operation down to 4V input. |
| Flicker-free spread spectrum | 25% triangle modulation (enabled via SYNC/SPRD = INTVCC) reduces EMI peak amplitude by >10dB without compromising regulation or transient response. |
| Open/short LED fault reporting | FAULT pin asserts open-drain low during VFB > 0.95V (open) or VFB < 0.25V (short); latching behavior configurable via SS resistor (499kΩ = latch-off). |
| AEC-Q100 Grade I qualification | Validated for automotive use across –40°C to +125°C; includes HTOL, TC, ESD, and EM immunity testing per ISO 16750 and AEC standards. |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
|
Use Scenario: Adaptive front-lighting system (AFS) with dynamic beam shaping and daytime running light (DRL) integration. IC Role / Device Role / Timing Role: Primary LED current controller managing multiple strings (e.g., low-beam, high-beam, cornering) with synchronized 2MHz switching. Use Value: Seamless buck-boost transitions prevent beam flicker during battery voltage sag (e.g., engine start), while ±3% current accuracy ensures consistent photometric output across vehicle lifetime. |
Use Scenario: 100W+ LED fixture for warehouse or factory floor illumination powered from 24V or 48V DC distribution bus. IC Role / Device Role / Timing Role: Constant-current LED driver enabling high-efficiency (>94% at 2MHz) operation with minimal heatsink requirement. Use Value: 2MHz switching allows use of 2.2µH inductors and 22µF ceramic output caps - reducing board area by >35% vs. 500kHz alternatives while maintaining low EMI. |
| Avionics Cabin Lighting | Battery-Powered Emergency Lighting |
|
Use Scenario: Dimmable LED modules in commercial aircraft cabins requiring DO-160G Class D lightning surge immunity and low EMI. IC Role / Device Role / Timing Role: LED driver with spread-spectrum modulation and robust fault handling for certified safety-critical lighting. Use Value: Integrated 25% triangle spread spectrum meets stringent DO-160G radiated emissions limits without external filtering; FAULT pin enables system-level health monitoring. |
Use Scenario: Portable emergency egress lighting powered by 12V sealed lead-acid or LiFePO4 battery with wide discharge range (10V–14.4V). IC Role / Device Role / Timing Role: Wide-input buck-boost controller sustaining constant LED brightness from battery end-of-life (10V) to full charge (14.4V). Use Value: 4V–60V input range covers full battery voltage envelope; 2000:1 external PWM dimming enables ultra-low standby current (<2µA shutdown) and smooth fade-in/fade-out. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8391AEUFD#PBF | Same silicon, rated for –40°C to +125°C but not AEC-Q100 qualified; identical electrical specs and pinout. | Non-automotive industrial or consumer lighting where automotive reliability certification is not required. | Select when AEC-Q100 is unnecessary and cost sensitivity favors non-automotive grade. |
| LT8390AIUFD#PBF | Predecessor device; supports only 600kHz–1.5MHz switching, no spread spectrum, lower max VOUT (45V), and no PWMTG output. | Legacy designs requiring backward compatibility or lower-frequency EMI filtering; lacks flicker-free dimming capability. | Choose only for drop-in replacement in existing LT8390-based boards; not recommended for new designs requiring 2MHz or spread spectrum. |
Compared with LT8391AEUFD#PBF, the LT8391AIUFD#PBF adds AEC-Q100 qualification and tighter production screening for automotive use; versus LT8390AIUFD#PBF, it delivers higher frequency, spread spectrum, and enhanced dimming architecture - enabling smaller magnetics, lower EMI, and superior lighting quality.
Availability
LT8391AIUFD#PBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and avionics cabin lighting requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.
Supply support for LT8391AIUFD#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 delivers high-frequency, wide-input-range LED controllers optimized for automotive lighting systems requiring AEC-Q100 qualification, seamless topology transitions, and flicker-free dimming performance.
FAQ
What is the maximum LED string voltage supported by the LT8391AIUFD#PBF?
The LT8391AIUFD#PBF supports output voltages up to 60V, with reliable operation confirmed for LED strings up to 51V forward voltage in typical applications. Its 0V to 60V VOUT range enables direct driving of multi-LED series strings without intermediate voltage conversion stages, and its open/short LED protection circuitry remains fully functional across this entire range.
Does the LT8391AIUFD#PBF require external bootstrap diodes for TG1/TG2 operation?
No, the LT8391AIUFD#PBF integrates Schottky bootstrap diodes from INTVCC to BST1 and BST2. External bootstrap capacitors (e.g., 0.1µF X7R ceramic) must be placed between BST1–SW1 and BST2–SW2, but discrete bootstrap diodes are unnecessary - simplifying layout and improving reliability in high-vibration automotive environments.
How does the LT8391AIUFD#PBF handle transitions between buck, buck-boost, and boost modes?
The LT8391AIUFD#PBF uses proprietary peak-buck/peak-boost current mode control to achieve seamless, low-noise transitions. Transition points are precisely defined (e.g., buck-to-buck-boost at VIN/VOUT = 1.25), and the controller maintains continuous conduction mode without regulation discontinuity or audible artifacts - verified in automotive headlamp EMC testing.
Can the LT8391AIUFD#PBF be synchronized to an external clock?
Yes, the LT8391AIUFD#PBF supports external synchronization via the SYNC/SPRD pin. When driven with a TTL/CMOS clock signal (600kHz–2.1MHz), the internal oscillator locks to the external frequency with minimal jitter. This enables EMI reduction through frequency alignment in multi-rail systems and eliminates beat frequencies in densely packed PCBs.
What fault protection features are implemented in the LT8391AIUFD#PBF?
The LT8391AIUFD#PBF provides open LED (VFB > 0.95V & V(ISP-ISN) < 10mV), short LED (VFB < 0.25V), and overvoltage (VFB > 1.05V) protection. Fault status is reported on the open-drain FAULT pin, and behavior (hiccup, latch-off, or keep-running) is configured via an external resistor on the SS pin - enabling system-level fault strategy customization.
LT8391AIUFD#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:
- 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-QFN (4x5)
LT8391AIUFD#PBF FAQ
1.How can I place an order for LT8391AIUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391AIUFD#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 LT8391AIUFD#PBF reliable?
The price and inventory of LT8391AIUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391AIUFD#PBF is usually 5 days.
3.What payment methods are accepted for LT8391AIUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391AIUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391AIUFD#PBF?
LT8391AIUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391AIUFD#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 LT8391AIUFD#PBF?
For technical support, including LT8391AIUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391AIUFD#PBF requirements.
6.How does Aetrix verify that LT8391AIUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LT8391AIUFD#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 LT8391AIUFD#PBF meets industry standards.
7.What is the process for return or replacement of LT8391AIUFD#PBF?
All LT8391AIUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391AIUFD#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 LT8391AIUFD#PBF part is unused and in its original packaging.
Return procedure for LT8391AIUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT8391AIUFD#PBF Tags
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BCR402RE6327HTSA1
Infineon Technologies
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BCR430UXTSA2
Infineon Technologies
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BCR420UE6433HTMA1
Infineon Technologies
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BCR420UE6327HTSA1
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BCR421UE6327HTSA1
Infineon Technologies
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LYT1604D-TL
Power Integrations
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HV9910CLG-G
Microchip Technology
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CL2N8-G
Microchip Technology
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BCR420UW6-7
Diodes Incorporated
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BCR421UW6-7
Diodes Incorporated
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BCR420UFD-7
Diodes Incorporated
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BCR421UFD-7
Diodes Incorporated
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