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Analog Devices Inc. LT8391DJUFDM#WTRPBF
- Part No.:
- LT8391DJUFDM#WTRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT8391DJUFDM#WTRPBF.pdf
- Description:
- 60VSYNC 4-SWITCH BUCK-BOOST LED
- Quantity:
- Payment:
- Shipping:
Inventory:3,044
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Product details
Overview
LT8391DJUFDM#WTRPBF from Analog Devices is a synchronous 4-switch buck-boost LED controller IC that regulates constant LED current across input voltages from 4V to 60V and output voltages from 0V to 60V. It employs proprietary peak-buck/peak-boost current mode control, supports 150kHz–650kHz fixed-frequency or ±15% spread-spectrum operation, and delivers ±4% LED current accuracy at 100mV full scale-enabling flicker-free automotive headlamp and running lamp drivers.
For engineers reviewing the LT8391DJUFDM#WTRPBF datasheet, LT8391DJUFDM#WTRPBF pinout, LT8391DJUFDM#WTRPBF application, or LT8391DJUFDM#WTRPBF equivalent, key selection criteria include its AEC-Q100 qualification, seamless buck/buck-boost/boost region transitions, open/short LED fault reporting via FAULT pin, and support for both PWM and 20:1 analog dimming with CTRL pin interface.
Technical Context
The LT8391DJUFDM#WTRPBF implements a dual-path current-mode architecture with separate buck and boost comparators (A3 and A4), enabling smooth mode transitions without discontinuities. Its VC pin serves as a diode-OR of two error amplifiers (EA1 and EA2), allowing unified compensation for both constant-voltage (FB loop) and constant-current (ISP/ISN loop) regulation.
Operation is governed by VIN/VOUT ratio: buck region (VIN/VOUT > 1.18), buck-boost region (0.85 < VIN/VOUT < 1.18), and boost region (VIN/VOUT < 0.75), with hysteresis preventing chatter. Internal charge paths maintain BST1/BST2 bootstrap voltage during sustained buck or boost operation, eliminating need for external charge pumps.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 60V - supports 12V/24V/48V automotive and industrial battery inputs without pre-regulation |
| VOUT Range | 0V to 60V - enables single-inductor LED string drive from sub-LED to over-LED voltage conditions |
| Switching Frequency | 150kHz to 650kHz - adjustable via RT resistor; ±15% triangle spread spectrum reduces EMI peaks |
| LED Current Accuracy | ±4% at 100mV full scale - ensures consistent luminance across temperature and line/load variations |
| Efficiency | Up to 98% at 25V/2A - achieved via synchronous 4-switch topology and low RDS(on) gate drivers (TG1/TG2: 2.6Ω pull-up) |
| Fault Protection | Open LED (VFB > 0.95V), short LED (VFB < 0.05V), and overvoltage (VFB > 1.05V) - reported on open-drain FAULT pin |
| Operating Temp | –40°C to +150°C junction - qualified per AEC-Q100 Grade 1 for under-hood automotive use |
Pinout & Package
LT8391DJUFDM#WTRPBF is housed in a 28-lead (4mm × 5mm) plastic side-wettable QFN package (UFDM) with exposed thermal pad (Pin 29 = GND). The package supports automated optical inspection (AOI) and provides θJA = 34°C/W and θJC = 3.4°C/W for high-power LED driver thermal management.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TG1 (1) | Buck-side top gate driver | Drives buck-side high-side NMOS (A) with swing from SW1 to BST1; enables synchronous buck operation |
| LSP/LSN (2,3) | Buck inductor current sense inputs | Kelvin-connected to RSENSE; provide accurate inductor current for peak-buck control and reverse-current detection |
| VIN (4) | Main input supply rail | Determines operating region (buck/buck-boost/boost); powers INTVCC LDO and internal circuitry |
| INTVCC (5) | Internal 5V LDO output | Supplies gate drivers and control logic; requires ≥4.7µF local ceramic bypass for stability |
| EN/UVLO (6) | Enable and input UVLO input | 1.220V falling threshold enables programmable VIN UVLO with hysteresis via resistor divider |
| PWM (8) | Digital dimming input | Accepts 0–>1.5V logic pulses; forces TG1/TG2 off and BG1/BG2 on when low for fast LED shutdown |
| CTRL (10) | Analog dimming control | Sets LED current threshold: ILED = Min(VCTRL−0.25V,1V)/(10·RLED) - enables 20:1 linear dimming range |
| ISP/ISN (11,12) | LED current sense inputs | Kelvin-connected to RLED; regulate LED current with ±4% accuracy referenced to VCTRL |
| FAULT (14) | Open-drain fault indicator | Pulled low on open LED (VFB>0.95V), short LED (VFB<0.05V), or FB overvoltage (VFB>1.05V) |
| SS (15) | Soft-start timer input | Charged by 12.5µA internal current; sets startup ramp time and selects fault mode (hiccup/latchoff/keep-running) |
| FB (16) | Voltage feedback input | Regulated to 1.00V for CV mode; used for LED open/short detection and overvoltage protection |
| VC (17) | Error amplifier output | Diode-OR of EA1/EA2 outputs; sets current comparator thresholds for seamless CV/CC transition |
| RT (18) | Frequency setting input | Resistor to GND sets oscillator frequency from 150kHz (226kΩ) to 650kHz (100kΩ) |
| SPRD (19) | Spread spectrum enable | GND = fixed frequency; INTVCC = ±15% triangle modulation for EMI reduction |
| VOUT (21) | Output supply rail | Determines operating region; supplies PWMTG drive rail; requires ≥1µF local ceramic bypass |
| TG2 (22) | Boost-side top gate driver | Drives boost-side high-side NMOS (C) with swing from SW2 to BST2; enables synchronous boost operation |
| SW2 (23) | Boost switch node | Swings from Schottky drop below GND to VOUT; connects to boost inductor and C MOSFET source |
| BST2 (24) | Boost bootstrap supply | Charged via internal Schottky from INTVCC; requires external capacitor to SW2 for high-side gate drive |
| BG2/BG1 (25,26) | Bottom gate drivers | Drive buck/boost low-side NMOS (B/D) with 0–INTVCC swing; RDS(on) = 1.2Ω pull-down for fast turn-off |
| BST1 (27) | Buck bootstrap supply | Charged via internal Schottky from INTVCC; requires external capacitor to SW1 for buck high-side drive |
| SW1 (28) | Buck switch node | Swings from Schottky drop below GND to VIN; connects to buck inductor and A MOSFET source |
| GND (13,29) | Power and signal ground | Exposed pad (Pin 29) must be soldered to PCB ground plane for thermal and EMI performance |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor 4-switch architecture | Eliminates need for separate buck and boost converters; reduces BOM count and board area in wide-input LED systems |
| Seamless buck/buck-boost/boost transitions | No output disturbance or current discontinuity when VIN crosses VOUT - critical for stable illumination in automotive transients |
| AEC-Q100 Grade 1 qualification | Validated for –40°C to +150°C operation with enhanced reliability testing - suitable for front-end automotive lighting |
| Integrated 5V INTVCC LDO | Provides regulated supply for gate drivers and logic; eliminates need for external bias rail and simplifies power tree |
| Programmable fault response | SS pin resistor selects hiccup (no resistor), latch-off (499kΩ), or keep-running (100kΩ) behavior during LED faults |
| No top-MOSFET refresh noise | Proprietary control avoids gate-refresh spikes in pure buck or boost modes - reduces conducted EMI in sensitive RF environments |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive driving beam (ADB) headlamps requiring precise current regulation across 9–16V battery range and 30–60V LED string voltages. IC Role / Device Role / Timing Role: Primary LED current controller managing four external MOSFETs in synchronous 4-switch buck-boost topology. Use Value: Maintains ±4% LED current accuracy over temperature and line variation, ensuring consistent photometric output and compliance with ECE/SAE standards. | Use Scenario: High-efficiency 50W+ LED fixtures powered from 24VDC or 48VDC industrial power rails with variable LED string configurations. IC Role / Device Role / Timing Role: Constant-current LED driver IC supporting 0–60V output and seamless mode transitions during dimming or load changes. Use Value: Delivers up to 98% efficiency at 25V/2A, reducing thermal load and enabling compact heatsink design in enclosed luminaires. |
| Emergency Vehicle Warning Lights | Off-Road LED Light Bars |
Use Scenario: Flashing red/blue warning lights subjected to wide input transients (load dump, cold crank) and extreme ambient temperatures. IC Role / Device Role / Timing Role: Robust LED controller with AEC-Q100 qualification, open/short LED fault reporting, and –40°C to +150°C operation. Use Value: Fault pin asserts during LED failure, enabling system-level diagnostics and fail-safe behavior without external monitoring circuitry. | Use Scenario: 12V/24V vehicle-mounted light bars driving long LED strings where input may dip below output during cranking. IC Role / Device Role / Timing Role: Wide-input buck-boost LED driver enabling operation from 4V to 60V with no external pre-regulator. Use Value: Eliminates brownout-induced flicker during engine start by maintaining regulation down to 4V input - critical for safety-critical lighting. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3789EMSE#PBF | 4-switch buck-boost DC/DC controller (not LED-specific); lacks integrated LED current sense amplifier, FAULT pin, and CTRL-based analog dimming | Requires external current sense amp and fault logic; suited for general-purpose power conversion, not optimized for LED current regulation | Choose LTC3789EMSE#PBF only if designing non-LED constant-power or constant-voltage loads with similar VIN/VOUT ranges |
| LT3762EFE#PBF | Boost-only LED controller with integrated high-side PMOS switch; limited to VOUT > VIN; no buck or buck-boost capability | Cannot regulate when VIN > VOUT; unsuitable for automotive headlamps with variable LED string counts | Choose LT3762EFE#PBF only for fixed-boost LED applications where input never exceeds output voltage |
Compared with LTC3789EMSE#PBF and LT3762EFE#PBF, the LT8391DJUFDM#WTRPBF uniquely integrates LED-specific functions-including ISP/ISN current sensing, FAULT reporting, CTRL-based analog dimming, and AEC-Q100 qualification-making it the only direct solution for automotive-grade, wide-range LED current regulation.
Availability
LT8391DJUFDM#WTRPBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and emergency vehicle warning lights requiring stable component supply, AEC-Q100 compliance, and seamless buck-boost operation.
Supply support for LT8391DJUFDM#WTRPBF 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 leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT8391D product line was designed specifically for high-reliability, wide-input-range LED driver applications in automotive and industrial environments-emphasizing seamless mode transitions, integrated fault protection, and AEC-Q100 qualification.
FAQ
What is the maximum output voltage supported by the LT8391DJUFDM#WTRPBF?
The LT8391DJUFDM#WTRPBF supports an output voltage range of 0V to 60V. This allows it to drive LED strings with forward voltages spanning from a single LED to long series strings, while maintaining regulation even when input voltage falls below output voltage - a key requirement for automotive cranking conditions and multi-configuration lighting systems. The 60V absolute maximum rating also accommodates transient overvoltages common in automotive environments.
How does the LT8391DJUFDM#WTRPBF handle LED open-circuit and short-circuit faults?
The LT8391DJUFDM#WTRPBF detects LED open-circuit when FB voltage exceeds 0.95V and short-circuit when FB voltage drops below 0.05V. Upon detection, it pulls the open-drain FAULT pin low. The fault response mode - hiccup, latch-off, or keep-running - is selected via a resistor on the SS pin (no resistor, 499kΩ, or 100kΩ respectively). This configurable behavior enables system-level fault handling without additional supervision circuitry, and is fully documented in the LT8391DJUFDM#WTRPBF datasheet Section "Start-Up and Fault Protection".
Can the LT8391DJUFDM#WTRPBF operate with both PWM and analog dimming simultaneously?
No, the LT8391DJUFDM#WTRPBF does not support simultaneous PWM and analog dimming. The PWM pin overrides the CTRL pin: when PWM is driven low, TG1 and TG2 are turned off and BG1 and BG2 are turned on, disconnecting the VC pin and halting regulation. Analog dimming via CTRL is active only during PWM high states. For combined dimming, external logic must coordinate PWM duty cycle and CTRL voltage - for example, using PWM to set coarse brightness levels and CTRL to fine-tune within each level. This behavior is defined in the LT8391DJUFDM#WTRPBF PIN FUNCTIONS section for Pin 8 (PWM).
What thermal management requirements apply to the LT8391DJUFDM#WTRPBF in high-power LED applications?
The LT8391DJUFDM#WTRPBF uses a 28-lead side-wettable QFN (UFDM) package with an exposed thermal pad (Pin 29 = GND) that must be soldered directly to the PCB ground plane. With θJA = 34°C/W and θJC = 3.4°C/W, effective thermal design requires ≥200mm² copper area under the pad, multiple thermal vias (≥6×0.3mm), and connection to internal ground planes. In 50W applications (e.g., 25V/2A), junction temperature must remain ≤150°C - achievable with proper layout and ambient ≤85°C. Thermal shutdown activates at ~165°C but is intended only for fault protection, not continuous operation.
Is the LT8391DJUFDM#WTRPBF pin-compatible with earlier LT8391 variants such as the LT8391JUFDM#PBF?
Yes, the LT8391DJUFDM#WTRPBF is pin-compatible with the LT8391JUFDM#PBF and other LT8391x UFDM-package variants. All share identical 28-pin UFDM footprint, pinout, and electrical characteristics. The "WTRPBF" suffix denotes tape-and-reel packaging with automotive-grade traceability and extended temperature screening (–40°C to +150°C), while functional behavior matches the base LT8391D silicon. No PCB layout changes are required when upgrading from LT8391JUFDM#PBF to LT8391DJUFDM#WTRPBF in automotive designs.
LT8391DJUFDM#WTRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN 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:
- 0V ~ 60V
- Current - Output / Channel:
- -
- Frequency:
- 150kHz ~ 650kHz
- Dimming:
- Analog, PWM
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q100
- Mounting Type:
- Surface Mount, Wettable Flank
- Supplier Device Package:
- 28-QFN (4x5)
LT8391DJUFDM#WTRPBF FAQ
1.How can I place an order for LT8391DJUFDM#WTRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391DJUFDM#WTRPBF 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 LT8391DJUFDM#WTRPBF reliable?
The price and inventory of LT8391DJUFDM#WTRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391DJUFDM#WTRPBF is usually 5 days.
3.What payment methods are accepted for LT8391DJUFDM#WTRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391DJUFDM#WTRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391DJUFDM#WTRPBF?
LT8391DJUFDM#WTRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391DJUFDM#WTRPBF 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 LT8391DJUFDM#WTRPBF?
For technical support, including LT8391DJUFDM#WTRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391DJUFDM#WTRPBF requirements.
6.How does Aetrix verify that LT8391DJUFDM#WTRPBF is sourced from the original manufacturer or authorized distributors?
All LT8391DJUFDM#WTRPBF 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 LT8391DJUFDM#WTRPBF meets industry standards.
7.What is the process for return or replacement of LT8391DJUFDM#WTRPBF?
All LT8391DJUFDM#WTRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391DJUFDM#WTRPBF, 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 LT8391DJUFDM#WTRPBF part is unused and in its original packaging.
Return procedure for LT8391DJUFDM#WTRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT8391DJUFDM#WTRPBF Tags
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BCR402RE6327HTSA1
Infineon Technologies
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BCR430UXTSA2
Infineon Technologies
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BCR420UE6433HTMA1
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BCR420UE6327HTSA1
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BCR421UE6327HTSA1
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LYT1604D-TL
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HV9910CLG-G
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CL2N8-G
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BCR420UW6-7
Diodes Incorporated
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BCR421UW6-7
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BCR420UFD-7
Diodes Incorporated
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BCR421UFD-7
Diodes Incorporated
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