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Analog Devices Inc. LT8391AIFE#TRPBF
- Part No.:
- LT8391AIFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT8391AIFE#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,132
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Product details
Overview
LT8391AIFE#TRPBF from Analog Devices is a synchronous 4-switch buck-boost LED controller 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 600kHz–2MHz. It delivers ±3% LED current accuracy, supports 2000:1 external PWM dimming, and integrates open/short LED fault detection with FAULT pin reporting - deployed in automotive headlamps and high-frequency industrial LED lighting.
For engineers reviewing the LT8391AIFE#TRPBF datasheet, LT8391AIFE#TRPBF pinout, LT8391AIFE#TRPBF application, or LT8391AIFE#TRPBF equivalent, key selection considerations include its 28-lead TSSOP package with exposed pad, AEC-Q100 qualification for automotive use, seamless region transitions (buck/buck-boost/boost), and dual analog dimming via CTRL1/CTRL2 with thermal derating capability.
Technical Context
The LT8391AIFE#TRPBF implements a proprietary peak-buck/peak-boost current mode architecture that uses a single inductor and shared ISP/ISN current sense path to maintain regulation continuity across VIN/VOUT ratios from 0.73 to >1.35. Its internal oscillator supports fixed-frequency operation (600kHz–2MHz) via RT resistor or synchronization via SYNC/SPRD pin, with optional 25% triangle spread spectrum for EMI reduction.
Control logic separates buck-side (TG1/BG1/LSP/LSN) and boost-side (TG2/BG2/SW2/BST2) gate drivers, each with dedicated bootstrap supplies and <25ns rise/fall times. The VC error amplifier output interfaces with an external RC compensation network, while FB monitors output voltage for overvoltage, open-LED, and short-LED protection with latch-off/hiccup/keep-running fault modes selectable via SS pin resistor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Synchronous 4-switch buck-boost with single-inductor architecture enabling continuous regulation when VIN < VOUT, VIN > VOUT, or VIN ≈ VOUT |
| Input Voltage Range | 4V to 60V - supports wide automotive battery transients (4V–56V transient, 6V–32V continuous) |
| Output Voltage Range | 0V to 60V - accommodates up to 51V LED string with direct VOUT sensing |
| Switching Frequency | 600kHz to 2MHz adjustable via RT pin or synchronizable externally - enables compact magnetics and low EMI with spread spectrum option |
| LED Current Accuracy | ±3% at 100mV full-scale sense voltage - ensures stable brightness 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-side PMOS PWMTG drive |
| Fault Protection | Dedicated open-LED (VFB > 0.95V & V(ISP−ISN) < 10mV), short-LED (VFB < 0.25V), and overvoltage (VFB > 1.05V) detection with FAULT pin reporting |
Pinout & Package
LT8391AIFE#TRPBF is housed in a 28-lead plastic TSSOP package with exposed pad (FE package), rated for –40°C to +125°C junction temperature, θJA = 30°C/W, θJC = 5°C/W. Exposed pad (Pin 29) must be soldered to PCB ground plane for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ISP / ISN | LED current sense differential inputs | Kelvin-connected inputs for accurate LED current regulation; full-scale threshold programmable from 0–100mV via CTRL1/CTRL2 |
| LSP / LSN | Buck-side inductor current sense differential inputs | Enable reverse-current detection and peak-buck current mode control; referenced to buck switch node SW1 |
| TG1 / BG1 / BST1 / SW1 | Buck-side power switch interface | TG1 drives top N-MOSFET gate (SW1→BST1 swing); BG1 drives bottom N-MOSFET (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 (GND→INTVCC); BST2 supplies bootstrap for TG2 |
| PWMTG | High-side PMOS PWM switch driver | Inverted buffered PWM output driving external PMOS; rail-to-rail swing between (VOUT–5V) and VOUT ensures clean turn-on/turn-off |
| CTRL1 / CTRL2 | Analog dimming and thermal derating inputs | CTRL1 sets LED current scale (0.25V–2V → 0–100mV threshold); CTRL2 applies negative-tempco derating curve |
| FAULT | Open-drain fault status output | Pulled low during open-LED, short-LED, or overvoltage events; updated only during PWM high time and latched low otherwise |
| SS | Soft-start and fault-mode configuration | Capacitor sets soft-start ramp time; resistor to VREF selects hiccup (no resistor), latch-off (499kΩ), or keep-running (100kΩ) on fault |
Key Features
| Feature | Design Value |
|---|---|
| Proprietary peak-buck/peak-boost control | Enables seamless, low-noise transitions between buck, buck-boost, and boost regions without discontinuity or audible artifacts |
| 25% triangle spread spectrum | Reduces peak EMI by spreading switching energy across a 21–25% bandwidth above base frequency - meets CISPR 25 Class 5 requirements |
| High-side PMOS PWM driver (PWMTG) | Eliminates top-MOSFET refresh noise in both buck and boost modes - critical for flicker-sensitive automotive lighting |
| AEC-Q100 qualified (Grade I) | Validated for automotive applications including headlamps and DRLs; operates reliably from –40°C to +125°C junction temperature |
| Dual analog dimming with thermal derating | CTRL1 sets baseline current; CTRL2 injects temperature-dependent scaling - prevents LED thermal runaway in enclosed fixtures |
| Configurable fault response | SS pin resistor selects behavior on LED fault: hiccup (auto-retry), latch-off (shutdown until reset), or keep-running (maintains regulation if possible) |
Applications
| Automotive Headlamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) with matrix LED arrays requiring precise current control across 9–16V battery range and cold-crank (4.5V) conditions. IC Role / Device Role / Timing Role: Primary LED current controller managing up to 51V, 1.5A strings; handles seamless buck-to-boost transition during voltage dips. Use Value: ±3% current accuracy ensures consistent lumen output; 2MHz operation minimizes inductor size for space-constrained headlamp modules. |
Use Scenario: Outdoor high-mast lighting powered by 48V DC microgrids, operating in ambient temperatures from –40°C to +85°C. IC Role / Device Role / Timing Role: Constant-current regulator for multi-string 40V LED loads; uses CTRL2 thermal derating to reduce current as heatsink temperature rises. Use Value: AEC-Q100 qualification ensures long-term reliability; 60V absolute max ratings tolerate 48V bus transients up to 60V. |
| Avionics Cabin Lighting | Medical Surgical Lighting |
Use Scenario: FAA-certified cabin LED lighting powered from 28V aircraft bus with strict EMI limits and zero-flicker requirements. IC Role / Device Role / Timing Role: Flicker-free LED driver using internal PWM dimming and spread spectrum; FAULT pin reports open-circuit for redundancy monitoring. Use Value: 2000:1 external PWM dimming enables smooth 0.1–100% intensity control; no top-MOSFET refresh noise eliminates visible artifacts. |
Use Scenario: Sterile-field surgical lights requiring ultra-stable color temperature and zero electromagnetic interference with sensitive imaging equipment. IC Role / Device Role / Timing Role: Precision current source for RGBW LED engines; FB loop provides overvoltage protection to prevent LED overdrive during calibration. Use Value: 94% efficiency at 2MHz reduces thermal load in sealed enclosures; ±3% current accuracy maintains CCT stability across power cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3965EFE#TRPBF | 4-switch buck-boost LED controller with integrated MOSFETs (40V max), lower VIN range (4.5V–60V), no spread spectrum, 1000:1 PWM dimming | Targeted at lower-power (<15W), space-constrained designs where integrated FETs eliminate external gate drivers | Select when board area is critical and 40V output compliance suffices; not suitable for 51V LED strings or EMI-sensitive automotive systems |
| LM3423MH/NOPB | Asynchronous boost-only LED controller (no buck-boost), 6V–75V input, 1.5A max, no internal PWM, requires external PWM generator | Designed for fixed-boost LED applications like signage where VIN always < VOUT and cost is primary constraint | Choose only when topology is strictly boost-only and thermal derating or spread spectrum are unnecessary |
Compared with LT3965EFE#TRPBF and LM3423MH/NOPB, the LT8391AIFE#TRPBF uniquely supports true buck-boost operation with seamless region transitions, 25% spread spectrum for EMI suppression, and dual analog dimming with thermal derating - making it the only option qualified for AEC-Q100 automotive headlamp systems requiring 0–60V output flexibility.
Availability
LT8391AIFE#TRPBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and avionics cabin lighting requiring stable component supply, AEC-Q100 compliance, and long-lifecycle support.
Supply support for LT8391AIFE#TRPBF 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 instrumentation, industrial automation, and automotive safety systems.
The LT8391A product line delivers high-efficiency, high-frequency LED controllers optimized for automotive-grade reliability, EMI robustness, and seamless buck-boost operation - addressing stringent requirements of adaptive lighting and mission-critical illumination systems.
FAQ
What is the operating temperature range for the LT8391AIFE#TRPBF?
The LT8391AIFE#TRPBF is specified for operation from –40°C to +125°C junction temperature. This Grade I rating aligns with AEC-Q100 requirements for automotive under-hood and headlamp applications. Thermal derating is supported via CTRL2 input, and the exposed pad must be soldered to PCB ground for effective heat dissipation per θJC = 5°C/W specification.
How does the LT8391AIFE#TRPBF handle transitions between buck, buck-boost, and boost modes?
The LT8391AIFE#TRPBF uses a proprietary peak-buck/peak-boost current mode control scheme that continuously monitors VIN/VOUT ratio and adjusts switching behavior without discontinuity. Transition thresholds are precisely defined: buck-to-buck-boost at VIN/VOUT = 0.75, buck-boost-to-boost at 0.85, and boost-to-buck-boost at 0.98 - ensuring low-noise, flicker-free operation during battery voltage fluctuations.
Can the LT8391AIFE#TRPBF drive high-side PMOS switches directly?
Yes - the LT8391AIFE#TRPBF includes the PWMTG pin, a dedicated buffered and inverted PWM output designed to drive external high-side PMOS switches. It swings from (VOUT – 5V) to VOUT, providing sufficient gate drive margin for clean turn-on/turn-off and eliminating top-MOSFET refresh noise common in buck and boost configurations.
What fault protection features does the LT8391AIFE#TRPBF provide?
The LT8391AIFE#TRPBF provides open-LED detection (VFB > 0.95V & V(ISP–ISN) < 10mV), short-LED detection (VFB < 0.25V), and overvoltage protection (VFB > 1.05V). Fault status is reported on the open-drain FAULT pin and can be configured for hiccup, latch-off, or keep-running behavior using a resistor from SS to VREF.
Is spread spectrum operation mandatory, or can the LT8391AIFE#TRPBF run at fixed frequency?
Spread spectrum is optional. The LT8391AIFE#TRPBF operates at fixed frequency (600kHz–2MHz) set by the RT resistor when SYNC/SPRD is grounded. To enable 25% triangle spread spectrum, tie SYNC/SPRD to INTVCC. For external clock synchronization, apply a TTL/CMOS signal within 600kHz–2100kHz to SYNC/SPRD.
LT8391AIFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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
LT8391AIFE#TRPBF FAQ
1.How can I place an order for LT8391AIFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391AIFE#TRPBF 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 LT8391AIFE#TRPBF reliable?
The price and inventory of LT8391AIFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391AIFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8391AIFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391AIFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391AIFE#TRPBF?
LT8391AIFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391AIFE#TRPBF 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 LT8391AIFE#TRPBF?
For technical support, including LT8391AIFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391AIFE#TRPBF requirements.
6.How does Aetrix verify that LT8391AIFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8391AIFE#TRPBF 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 LT8391AIFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8391AIFE#TRPBF?
All LT8391AIFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391AIFE#TRPBF, 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 LT8391AIFE#TRPBF part is unused and in its original packaging.
Return procedure for LT8391AIFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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