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Analog Devices Inc. LT8391HFE#PBF
- Part No.:
- LT8391HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT8391HFE#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,403
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Product details
Overview
LT8391HFE#PBF from Analog Devices is a synchronous 4-switch buck-boost LED controller that regulates constant LED current across input voltages (4V–60V) both above and below output voltage (0V–60V), using proprietary peak-buck/peak-boost current mode control. It delivers ±3% LED current accuracy at 100mV full-scale sense, supports 150kHz–650kHz adjustable switching frequency with spread spectrum EMI reduction, and operates up to 150°C junction temperature for automotive headlamp and high-power LED lighting systems.
For engineers reviewing the LT8391HFE#PBF datasheet, LT8391HFE#PBF pinout, LT8391HFE#PBF application, or LT8391HFE#PBF equivalent, key selection considerations include its 28-lead TSSOP package with exposed pad, AEC-Q100 qualification, dual analog dimming (CTRL1/CTRL2), integrated bootstrap diodes, open/short LED fault reporting via FAULT pin, and seamless region transitions between buck, buck-boost, and boost modes.
Technical Context
The LT8391HFE#PBF implements a proprietary peak-buck/peak-boost current mode architecture that uses a single inductor current sense resistor (LSP/LSN) and a shared error amplifier (VC) to maintain precise LED current regulation across all three operating regions. Its control logic dynamically selects gate drive timing-TG1/BG1 for buck, TG2/BG2 for boost, and fixed 85%/15% duty cycles for buck-boost-based on real-time VIN/VOUT ratio.
It integrates two independent 5V (INTVCC) and 2V (VREF) linear regulators, supports internal PWM dimming (up to 2000:1 via RP resistor) and external PWM dimming (via PWM pin), and provides programmable fault response (hiccup/latch-off/keep-running) via SS pin resistor configuration. The device features dedicated high-side PMOS driver (PWMTG) with VOUT-referenced swing and ±15% triangle spread spectrum operation when SYNC/SPRD is tied to INTVCC.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 60V - supports wide-input automotive battery (cold-crank to load-dump) and industrial DC bus applications. |
| VOUT Range | 0V to 60V - enables direct connection to LED strings up to 51V forward voltage without intermediate conversion. |
| LED Current Accuracy | ±3% at 100mV full scale - ensures stable luminance across temperature and line/load variations in safety-critical lighting. |
| Switching Frequency | 150kHz to 650kHz (adjustable via RT) - allows optimization of magnetics size vs. EMI performance; ±15% spread spectrum reduces peak emissions. |
| Operating Temp | –40°C to +150°C (junction) - qualified per AEC-Q100 Grade H for under-hood automotive LED drivers. |
| Dimming Ratio | 2000:1 external PWM / 128:1 internal PWM - enables flicker-free dimming down to 0.05% brightness for adaptive lighting systems. |
| Fault Protection | Open LED (VFB > 0.95V & V(ISP-ISN) < 10mV), short LED (VFB < 0.25V) - latched or hiccup response configurable via SS pin resistor. |
Pinout & Package
LT8391HFE#PBF is housed in a 28-lead plastic TSSOP package with exposed pad (pin 29), thermally optimized for high-power LED driver PCBs. The exposed pad must be soldered directly to the ground plane for thermal and electrical integrity (θJC = 5°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ISP / ISN | LED current sense differential inputs | Kelvin-connected to RLED for ±3% accurate current regulation; common-mode range 0V–60V supports high-side sensing. |
| CTRL1 / CTRL2 | Analog dimming and thermal derating inputs | Program LED current threshold (0–100mV) with 20:1 analog dimming ratio and temperature-dependent current foldback. |
| PWM / PWMTG | External PWM input and high-side PMOS gate driver | PWMTG swings from (VOUT –5V) to VOUT, enabling direct drive of external high-side PMOS switch for true high-side PWM dimming. |
| FAULT | Open-drain fault status output | Pulled low during open/short LED faults; status updated only during PWM high phase and latched during low phase. |
| SYNC/SPRD | Frequency synchronization or spread spectrum enable | Tie to INTVCC for ±15% triangle spread spectrum; ground for fixed-frequency operation; apply external clock for sync. |
| LSP / LSN | Buck-side inductor current sense inputs | Enable single-inductor 4-switch topology with reverse-current detection and seamless region transition control. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor architecture | Eliminates need for separate buck and boost converters; reduces BOM count and board space while enabling VIN ≷ VOUT operation. |
| Integrated bootstrap Schottky diodes (BST1/BST2) | Removes requirement for external bootstrap diodes, simplifying layout and improving reliability in high-temperature environments. |
| No top MOSFET refresh noise in buck/boost | Proprietary gate timing eliminates shoot-through and refresh transients, reducing conducted EMI and improving LED current stability. |
| Adjustable soft-start via SS pin capacitor | 0.1µF capacitor yields controlled ramp-up of FB regulation voltage; UVLO or thermal shutdown forces immediate SS discharge. |
| Three configurable fault responses | Hiccup (no SS resistor), latch-off (499k), or keep-running (100k) - enables system-level fault strategy alignment without firmware changes. |
Applications
| Automotive Head Lamps | High-Power Industrial Lighting |
|---|---|
Use Scenario: Adaptive driving beam (ADB) headlamps requiring dynamic LED current control across 6V–16V battery range with cold-crank immunity. IC Role / Device Role / Timing Role: Primary LED current controller managing 4-switch buck-boost topology with seamless region transitions and ±3% current accuracy. Use Value: Enables compliance with UNECE R149 photometric requirements through stable current regulation despite wide VIN variation and thermal drift. | Use Scenario: High-bay LED fixtures powered from 24V–48V DC microgrids in warehouses, with demand for 2000:1 dimming and thermal derating. IC Role / Device Role / Timing Role: Constant-current LED driver with dual analog dimming (CTRL1/CTRL2) and programmable thermal foldback for long-lifetime operation. Use Value: Delivers flicker-free dimming down to 0.05% brightness while maintaining color consistency and extending LED lifetime via active thermal management. |
| Battery-Powered Emergency Lighting | UV-C LED Disinfection Systems |
Use Scenario: Portable emergency egress lighting using Li-ion battery packs (3.0V–12.6V) driving multi-string white LEDs with low quiescent current. IC Role / Device Role / Timing Role: Wide-input buck-boost LED controller with 2.1µA VIN quiescent current (shutdown) and 270µA operating current at 1.1V EN/UVLO. Use Value: Extends battery runtime by >30% versus discrete solutions while supporting seamless transition from buck to boost as battery discharges. | Use Scenario: Pulsed UV-C LED arrays (275nm, 3.5V–4.2V VF) requiring precise current pulses up to 2A with fast turn-on/turn-off control. IC Role / Device Role / Timing Role: High-accuracy current controller with 90ns PWM-to-PWMTG propagation delay and 300ns PWMTG fall time for sub-millisecond pulse shaping. Use Value: Enables precise dosimetry control in medical-grade disinfection by delivering repeatable, jitter-free current pulses with <±3% amplitude tolerance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3965EFE#PBF | 4-switch buck-boost LED controller with I²C interface, 3.5V–60V VIN, but rated only to 125°C (not AEC-Q100). | Lacks AEC-Q100 qualification and automotive temp grade; supports digital dimming and fault diagnostics via I²C. | Select for non-automotive systems requiring programmable configuration and telemetry, not for under-hood deployment. |
| LM3423MH/NOPB | High-side N-channel controller with external FETs; 4.5V–65V VIN, no integrated gate drivers or spread spectrum; max 125°C operation. | Requires external high-side driver and bootstrap circuitry; no seamless region transition or integrated PWM dimming driver. | Select when discrete FET selection is required for ultra-high efficiency or voltage scaling beyond 60V, accepting higher design complexity. |
Compared with LT3965EFE#PBF and LM3423MH/NOPB, the LT8391HFE#PBF uniquely combines AEC-Q100 Grade H qualification, integrated bootstrap diodes, ±15% spread spectrum, and seamless buck/buck-boost/boost transitions - making it the only choice for automotive headlamp designs requiring single-chip reliability and EMI compliance across full temperature range.
Availability
LT8391HFE#PBF is available at Aetrix Electronics and suitable for automotive headlamps, high-power industrial lighting, battery-powered emergency lighting, and UV-C disinfection systems requiring stable component supply with guaranteed long-term availability.
Supply support for LT8391HFE#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, industrial automation, communications, and automotive markets.
The LT8391 product line was designed specifically for high-reliability, wide-input-range LED driver applications where seamless operation across buck, buck-boost, and boost topologies is required - especially in automotive lighting and harsh-environment industrial systems.
FAQ
What is the maximum junction temperature rating for the LT8391HFE#PBF?
The LT8391HFE#PBF is specified for operation from –40°C to +150°C junction temperature and is AEC-Q100 qualified for automotive Grade H applications. This rating is confirmed in the Order Information table (Rev. B datasheet, page 3), where LT8391H part numbers are explicitly listed with –40°C to 150°C temperature range. Thermal derating above 125°C is recommended for extended lifetime.
Does the LT8391HFE#PBF support spread spectrum operation, and how is it enabled?
Yes, the LT8391HFE#PBF supports ±15% triangle spread spectrum operation to reduce EMI peaks. It is enabled by tying the SYNC/SPRD pin to INTVCC, as stated in the FEATURES section (page 1) and PIN FUNCTIONS (page 13). When SYNC/SPRD = INTVCC, the internal oscillator modulates frequency around the RT-set center frequency with ±15% deviation, verified in Electrical Characteristics (page 6, "Highest Spread Spectrum Above Oscillator Frequency").
How does the LT8391HFE#PBF handle LED open-circuit and short-circuit faults?
The LT8391HFE#PBF detects open LED when VFB > 0.95V and V(ISP-ISN) < 10mV, and short LED when VFB < 0.25V. Fault status is reported on the open-drain FAULT pin, which pulls low during PWM high phase and latches during low phase. Response mode (hiccup, latch-off, or keep-running) is configured via resistor on the SS pin, as detailed in the PIN FUNCTIONS section (page 13) and Electrical Characteristics (page 6).
Can the LT8391HFE#PBF drive a high-side PMOS PWM switch, and what is the voltage range of the PWMTG pin?
Yes, the LT8391HFE#PBF includes a dedicated high-side PMOS driver on the PWMTG pin. Its output swings from the higher of (VOUT –5V) and 1.2V up to VOUT, enabling direct drive of external PMOS switches without level-shifting circuitry. This is confirmed in PIN FUNCTIONS (page 13): "PWMTG pin drives an external high side PMOS PWM switch with a voltage swing from the higher voltage of (VOUT –5V) and 1.2V to VOUT."
What is the purpose of the CTRL1 and CTRL2 pins on the LT8391HFE#PBF?
The CTRL1 pin sets the LED current regulation threshold (0–100mV) for 20:1 analog dimming with ±3% accuracy at full scale. The CTRL2 pin provides thermal derating capability - when connected to a negative temperature coefficient network, it linearly reduces LED current as temperature rises. Both functions are defined in PIN FUNCTIONS (pages 12–13) and Electrical Characteristics (page 5, "Full Scale LED Current Regulation").
LT8391HFE#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:
- 150kHz ~ 650kHz
- Dimming:
- Analog, PWM
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TSSOP-EP
LT8391HFE#PBF FAQ
1.How can I place an order for LT8391HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8391HFE#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 LT8391HFE#PBF reliable?
The price and inventory of LT8391HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8391HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT8391HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8391HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8391HFE#PBF?
LT8391HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8391HFE#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 LT8391HFE#PBF?
For technical support, including LT8391HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8391HFE#PBF requirements.
6.How does Aetrix verify that LT8391HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT8391HFE#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 LT8391HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT8391HFE#PBF?
All LT8391HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8391HFE#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 LT8391HFE#PBF part is unused and in its original packaging.
Return procedure for LT8391HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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