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Analog Devices Inc. LT8391IUFD#TRPBF
- Part No.:
- LT8391IUFD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT8391IUFD#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,007
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Product details
Overview
LT8391IUFD#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), featuring ±3% LED current accuracy, 150kHz–650kHz adjustable switching frequency, and integrated bootstrap diodes. It enables flicker-free high-power LED drivers for automotive headlamps and industrial lighting.
For engineers reviewing the LT8391IUFD#TRPBF datasheet, LT8391IUFD#TRPBF pinout, LT8391IUFD#TRPBF application, or LT8391IUFD#TRPBF equivalent, key selection criteria include VIN/VOUT crossover capability, 28-pin QFN (4mm × 5mm) package with exposed thermal pad, AEC-Q100 qualification, spread-spectrum EMI reduction, and dual analog dimming control via CTRL1/CTRL2 pins.
Technical Context
The LT8391IUFD#TRPBF implements ADI's proprietary peak-buck/peak-boost current mode control using a single inductor and shared current sense resistor (LSP/LSN), enabling seamless transitions between buck, buck-boost, and boost regions without audible noise or regulation discontinuity. Its region detection relies on real-time VIN/VOUT ratio monitoring with defined transition thresholds (e.g., buck-to-buck-boost at VIN/VOUT = 1.16–1.20).
It integrates two independent gate driver stages (TG1/BG1 for buck side; TG2/BG2 for boost side), each with matched pull-up/pull-down resistance (2.6Ω/1.4Ω for NMOS drivers), synchronized dead-time control (60ns TG-off-to-BG-on delay), and internal bootstrap diodes eliminating external Schottky requirements. The VC error amplifier output directly sets the current comparator threshold with 2000µS transconductance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 60V - supports wide-input battery systems including 12V/24V/48V automotive and industrial rails. |
| VOUT Range | 0V to 60V (51V LED max) - enables direct drive of multi-string high-voltage LED arrays without intermediate converters. |
| LED Current Accuracy | ±3% at 100mV full scale - ensures consistent luminance across temperature and unit variation in safety-critical lighting. |
| Switching Frequency | 150kHz to 650kHz (adjustable via RT pin) - allows optimization of magnetics size vs. EMI, with ±15% triangle spread spectrum for CISPR-25 compliance. |
| Dimming Ratio | 2000:1 external PWM + 128:1 internal PWM - delivers deep dimming without color shift in architectural and adaptive driving beam systems. |
| Package | 28-lead QFN (4mm × 5mm) with exposed GND pad - provides low θJC = 3.4°C/W for thermally demanding LED driver PCB layouts. |
| Temp Grade | –40°C to +125°C junction - qualified for under-hood automotive environments per AEC-Q100 Grade I. |
Pinout & Package
LT8391IUFD#TRPBF uses a 28-lead plastic QFN package (4mm × 5mm) with exposed thermal pad (Pin 29 = GND), θJA = 43°C/W, θJC = 3.4°C/W. The exposed pad must be soldered to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW1, SW2 | Buck/Boost switch nodes | High dv/dt nodes connecting to external MOSFET drains; require tight layout and Kelvin sense routing to LSP/LSN. |
| TG1, BG1, TG2, BG2 | NMOS gate drivers | Drive top/bottom FETs with matched 2.6Ω pull-up / 1.4Ω pull-down resistance; support 100% duty cycle in buck region. |
| LSP, LSN | Inductor current sense inputs | Kelvin-connected to single RSENSE for unified peak-buck/peak-boost current sensing across all operating regions. |
| ISP, ISN | LED current sense inputs | Differential inputs referenced to VOUT; enable ±10mV open-LED detection and 750mV overcurrent protection. |
| PWMTG | Inverted PWM top-gate driver | Drives external high-side PMOS with rail-to-rail swing (VOUT to VOUT–5V); eliminates need for level-shifting circuitry. |
| CTRL1, CTRL2 | Analog dimming & thermal derating inputs | Accept 0.25V–2V voltage inputs; provide 20:1 linear dimming and temperature-dependent current scaling without microcontroller. |
| SYNC/SPRD | Frequency control terminal | Ground = fixed oscillator; INTVCC = ±15% triangle spread spectrum; external clock = synchronization to system master. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor architecture | Eliminates separate buck/boost stages and associated magnetics, reducing BOM count by ≥30% and PCB area by 40% vs. cascaded solutions. |
| Proprietary peak-buck/peak-boost control | Ensures continuous conduction mode (CCM) operation and <1% LED current ripple during VIN/VOUT crossovers (e.g., cold crank 6V → 16V). |
| Integrated bootstrap diodes | Removes two external Schottky diodes per channel, simplifying layout and improving reliability in high-temp automotive applications. |
| Flicker-free spread spectrum | Triangle modulation reduces peak EMI by >10dB across 150–650kHz band, meeting CISPR-25 Class 5 without added shielding or filters. |
| AEC-Q100 Grade I qualification | Validated for automotive use including HTOL, TC, ESD, and EMC testing - supports ASIL-B system-level compliance when used with appropriate fault handling. |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive driving beam (ADB) systems requiring dynamic LED string reconfiguration across varying battery voltage (6–16V) and ambient temperature (–40°C to +125°C). IC Role / Device Role / Timing Role: Primary LED current controller managing up to 50W per channel with real-time region transition and fault reporting via FAULT pin. Use Value: Enables seamless dimming and zone control without current droop or flicker during engine start-stop cycles or load dump events. | Use Scenario: 100–200W warehouse lighting powered from 24VDC or 48VDC industrial power supplies with strict THD and EMI limits. IC Role / Device Role / Timing Role: Constant-current buck-boost regulator driving 3–5 series LED strings with programmable thermal derating via CTRL2. Use Value: Delivers 98% peak efficiency and ±3% current stability across 4V–60V input range, reducing heatsink size and energy cost over 50,000-hour lifetime. |
| Emergency Vehicle Lighting | UV-C Sterilization Systems |
Use Scenario: Flashing beacon modules requiring 2000:1 PWM dimming depth and robust open/short LED fault detection in vibration-prone mounting environments. IC Role / Device Role / Timing Role: High-reliability LED driver with latch-off or hiccup-mode fault response configured via SS pin resistor network. Use Value: Guarantees fail-safe operation with immediate FAULT pin assertion (<100ns propagation) upon LED string breakage or short circuit. | Use Scenario: Pulsed UV-C LED arrays (265nm, 1A pulses) demanding precise current regulation and fast turn-on/turn-off timing for germicidal efficacy. IC Role / Device Role / Timing Role: Precision current source with 50ns PWM-to-PWMTG propagation delay and <300ns PWMTG fall time for sub-millisecond pulse control. Use Value: Maintains calibrated irradiance dose per pulse while minimizing thermal stress on expensive UV-C LEDs through accurate 100mV full-scale sensing. |
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 in 28-lead TSSOP; same 4V–60V VIN, but fixed 200kHz–2MHz frequency (no spread spectrum); lacks PWMTG driver. | Targeted at space-constrained industrial lighting where EMI filtering is handled externally; not AEC-Q100 qualified. | Select when board area permits TSSOP and spread spectrum is unnecessary; verify external PWM switch implementation. |
| LM34927QMH/NOPB | 2-switch buck-boost LED controller (no true buck-boost topology); 6V–75V VIN, 0.5A max; no internal PWM dimming; requires external high-side switch. | Suitable for lower-power auxiliary lighting (≤15W); lacks seamless VIN/VOUT crossover and region transition logic. | Choose only for cost-sensitive non-automotive applications below 20W; cannot replace LT8391IUFD#TRPBF in headlamp or high-power designs. |
Compared with LT3965EFE#TRPBF and LM34927QMH/NOPB, the LT8391IUFD#TRPBF uniquely combines AEC-Q100 qualification, integrated spread spectrum, PWMTG driver, and true 4-switch architecture - making it the only option for automotive-grade, high-efficiency, single-inductor buck-boost LED drivers requiring <1% current ripple across full VIN/VOUT range.
Availability
LT8391IUFD#TRPBF is available at Aetrix Electronics and suitable for automotive headlamp systems, industrial high-bay lighting, emergency vehicle beacons, and UV-C sterilization equipment requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT8391IUFD#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. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT8391 product line was designed specifically for high-efficiency, high-reliability LED driver applications requiring seamless buck/boost/buck-boost operation - targeting automotive lighting, industrial solid-state lighting, and specialized medical/UV illumination systems.
FAQ
What is the maximum LED string voltage supported by the LT8391IUFD#TRPBF?
The LT8391IUFD#TRPBF supports an output voltage range of 0V to 60V, with a specified 51V LED string limit in typical applications. This is enforced by absolute maximum ratings (VOUT ≤ 60V) and internal fault protection thresholds (e.g., FB overvoltage at 1.05V). For 51V LED strings, the device maintains ±3% current accuracy and 98% peak efficiency at 25V/2A operation, as validated in the datasheet's TA01a reference design.
Does the LT8391IUFD#TRPBF require external bootstrap diodes?
No, the LT8391IUFD#TRPBF integrates bootstrap Schottky diodes from INTVCC to BST1 and BST2 pins, eliminating the need for external diodes. Each bootstrap pin (BST1/BST2) requires only an external ceramic capacitor (typically 0.1µF) connected to its respective switch node (SW1/SW2). This integration reduces component count, improves reliability in high-temperature environments, and simplifies PCB layout compared to controllers requiring discrete bootstrap diodes.
How does the LT8391IUFD#TRPBF handle transitions between buck, buck-boost, and boost modes?
The LT8391IUFD#TRPBF uses proprietary peak-buck/peak-boost current mode control with real-time VIN/VOUT ratio monitoring. Transition thresholds are precisely defined: buck-to-buck-boost at VIN/VOUT = 1.16–1.20, buck-boost-to-boost at 0.73–0.77, and peak-buck-to-peak-boost at 0.96–1.00. These boundaries ensure continuous conduction mode (CCM) operation and <1% LED current ripple during transitions - verified in Figure G04–G06 waveforms showing smooth IL behavior across all regions.
Can the LT8391IUFD#TRPBF be synchronized to an external clock?
Yes, the LT8391IUFD#TRPBF supports external synchronization via the SYNC/SPRD pin. When driven with a TTL/CMOS clock signal (150kHz–650kHz), the internal oscillator locks to the external frequency with minimal jitter. This capability enables EMI reduction through frequency dithering across multiple synchronized converters and deterministic timing for multi-channel ADB systems. The datasheet specifies SYNC/SPRD input bias current as ±0.1µA and threshold voltage as 0.4V–1.5V.
What fault protection features are implemented in the LT8391IUFD#TRPBF?
The LT8391IUFD#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 with configurable response modes (hiccup, latch-off, or keep-running) set via resistor selection on the SS pin. Propagation delay from fault occurrence to FAULT assertion is <100ns, and the FAULT pin updates only during PWM high state to avoid false triggers.
LT8391IUFD#TRPBF 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:
- 60V
- Current - Output / Channel:
- -
- Frequency:
- 150kHz ~ 650kHz
- 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)
LT8391IUFD#TRPBF FAQ
1.How can I place an order for LT8391IUFD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391IUFD#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 LT8391IUFD#TRPBF reliable?
The price and inventory of LT8391IUFD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391IUFD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8391IUFD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391IUFD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391IUFD#TRPBF?
LT8391IUFD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391IUFD#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 LT8391IUFD#TRPBF?
For technical support, including LT8391IUFD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391IUFD#TRPBF requirements.
6.How does Aetrix verify that LT8391IUFD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8391IUFD#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 LT8391IUFD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8391IUFD#TRPBF?
All LT8391IUFD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391IUFD#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 LT8391IUFD#TRPBF part is unused and in its original packaging.
Return procedure for LT8391IUFD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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