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Analog Devices Inc. LT3791HFE#PBF
- Part No.:
- LT3791HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3791HFE#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,792
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Product details
Overview
LT3791HFE#PBF from Analog Devices is a 60V synchronous 4-switch buck-boost LED driver controller in 38-lead TSSOP with exposed pad, operating from –40°C to 150°C junction temperature. It regulates LED current up to 52V output with input voltage ranging 4.7V–60V, supports True Color PWM™ and analog dimming, and achieves up to 98.5% efficiency in 100W (33.3V/3A) configurations for automotive headlamp systems.
For engineers reviewing the LT3791HFE#PBF datasheet, LT3791HFE#PBF pinout, LT3791HFE#PBF application, or LT3791HFE#PBF equivalent, key selection considerations include its seamless buck/boost/buck-boost transitions, ±6% LED current accuracy across 0–52V LED range, integrated open/short LED fault protection, and 200kHz–700kHz adjustable switching frequency with external synchronization capability.
Technical Context
The LT3791HFE#PBF implements constant-frequency forced-continuous conduction mode control with three independent feedback loops-LED current, input current, and output voltage-where the highest-priority loop dominates regulation. Its proprietary 4-switch single-inductor architecture eliminates top MOSFET refresh cycles in pure buck or boost operation, reducing switching losses and enabling smooth mode transitions near VIN ≈ VOUT.
Internal gate drivers support high-side N-channel MOSFETs via bootstrap supplies (BST1/BST2), with TG1/TG2 pull-up resistance of 2.6Ω and BG1/BG2 pull-down resistance of 1.2Ω at INTVCC = 5V. The VC pin serves dual roles as error amplifier output and current threshold modulator, scaling linearly from 0.7V to 1.9V to set SNSP–SNSN comparator trip points for both buck (–39mV to –56mV) and boost (+42mV to +60mV) operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.7V to 60V - supports wide automotive battery transients and industrial DC bus inputs without pre-regulation. |
| Output Voltage Capability | 0V to 60V (52V LED string max) - enables direct drive of multi-LED arrays without intermediate converters. |
| LED Current Accuracy | ±6% over 0V ≤ VLED < 52V - ensures consistent luminance across varying forward voltage and temperature. |
| Switching Frequency | 200kHz to 700kHz (adjustable via RT resistor or external SYNC) - balances EMI, efficiency, and magnetics size. |
| Junction Temperature Range | –40°C to 150°C - qualified for under-hood automotive and high-ambient industrial LED lighting. |
| Efficiency | Up to 98.5% at 100W (33.3V/3A) - minimizes thermal load and enables compact heatsink design. |
| Fault Protection | Open LED (FB > 1.15V), shorted LED (FB < 400mV), OVLO (>3V), and thermal shutdown - prevents system damage during failure modes. |
Pinout & Package
LT3791HFE#PBF uses a 38-lead plastic TSSOP package with exposed pad (Pin 39), which must be soldered to PCB ground plane for thermal and electrical integrity. θJA = 28°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CTRL (1) | Analog dimming threshold adjust | Sets LED current sense threshold from 6.5mV to 100mV; 1/10th of (VCTRL – 200mV) below 1.1V; clamps at full scale above 1.3V. |
| SS (2) | Soft-start and fault timer | Charged by 14µA current source during startup; latches off on open/short LED fault when pulled to VREF via 500kΩ. |
| PWM (3) | Digital dimming enable | Active-low signal halts switching, disconnects VC from external loads, and drives PWMOUT synchronously. |
| OPENLED (4) | Open-circuit LED fault indicator | Open-drain output asserting when FB > 1.15V and V(ISP–ISN) < 10mV - requires external pull-up. |
| SHORTLED (5) | Short-circuit LED fault indicator | Open-drain output asserting when FB < 400mV - requires external pull-up. |
| VREF (6) | 2.00V precision reference | Stable 2V output (±2%) used for CTRL biasing, dimming divider, and SS fault latch; supplies up to 200µA. |
| ISMON (7) | LED current monitor | 10× scaled replica of V(ISP–ISN); outputs 1V at 100mV sense voltage for diagnostics and closed-loop control. |
| IVINMON (8) | Input current monitor | 20× scaled replica of V(IVINP–IVINN); outputs 1V at 50mV sense voltage for input power limiting and telemetry. |
| EN/UVLO (9) | Enable and undervoltage lockout | 1.20V falling threshold with 15mV hysteresis; sub-µA bias above threshold; 3µA pull-down below threshold for precise resistor-divider programming. |
| IVINP/IVINN (10,11) | Input current sense inputs | Differential pair with 50mV threshold (±4mV) and 2.12mS transconductance for accurate input current regulation. |
| VIN (12) | Main power input | Accepts 4.7V–60V supply; bypassed to PGND with ≥4.7µF ceramic capacitor for stability and transient response. |
| INTVCC (13) | Internal 5V LDO output | Regulated 5.0V ±2% supply for logic and gate drivers; dropout <350mV at –10mA; current limit 67mA. |
| TG1/BST1/SW1 (14–16) | High-side buck switch drive | TG1 drives M1 top N-MOS; BST1 bootstraps TG1 gate above SW1; SW1 connects to VIN and inductor node. |
| PGND (17,20) | Power ground return | Low-impedance path for bottom MOSFET sources and high-current return; must tie closely to MOSFET source pads. |
| BG1/BG2 (18,19) | Low-side switch drivers | Drive M2/M3 gates from SGND to INTVCC; 3Ω pull-up / 1.2Ω pull-down typical at 5V. |
| SW2/BST2/TG2 (21,22,24) | High-side boost switch drive | TG2 drives M4 top N-MOS; BST2 bootstraps TG2 gate above SW2; SW2 connects to VOUT and inductor node. |
| ISP/ISN (25,26) | LED current sense inputs | Differential pair with 100mV default threshold (±2.5mV), adjustable via CTRL; 890µS transconductance. |
| SNSP/SNSN (27,28) | Current comparator inputs | Compare VC-derived threshold against sensed inductor current slope; buck threshold negative, boost positive. |
| SGND (30,39) | Signal ground reference | Reference for all small-signal circuitry; must connect to PGND at single point; exposed pad (39) is SGND. |
| PWMOUT (31) | Buffered PWM output | INTVCC-rail-to-rail buffered copy of PWM pin; drives external N-MOSFET for LED string disconnect. |
| CLKOUT (33) | Master clock output | In-phase oscillator signal at fSW; enables synchronization of multiple LT3791HFE#PBF controllers for parallel operation. |
| SYNC (34) | External clock input | Accepts 200kHz–700kHz external clock; internal 90kΩ pull-down enables simple resistor-divider frequency locking. |
| RT (35) | Oscillator frequency set | Resistor to SGND sets fSW: 147kΩ → 200kHz, 59.0kΩ → 400kHz, 29.1kΩ → 700kHz. |
| VC (36) | Error amplifier output & current threshold | 0.7V–1.9V control voltage setting SNSP–SNSN trip level; also compensation node for current loop stability. |
| FB (37) | Output voltage feedback | Regulates to 1.20V ±12mV; triggers OPENLED if >1.15V (rising) or SHORTLED if <400mV (falling). |
| OVLO (38) | Overvoltage lockout | Shuts down converter if >3.0V (±150mV); resets soft-start and disables switching until OVLO falls below 2.925V. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor topology | Enables continuous VIN-above-VOUT (buck), VIN-below-VOUT (boost), and VIN-near-VOUT (buck-boost) operation without mode discontinuities or audible artifacts. |
| True Color PWM™ dimming | Maintains full LED spectral fidelity and color consistency across 0–100% duty cycle by preserving constant current amplitude during PWM on-time. |
| No top MOSFET refresh cycle | Eliminates unnecessary switching in pure buck or boost regions, reducing gate drive loss and improving efficiency by ~1–2% at 500kHz. |
| VOUT disconnected from VIN during shutdown | Ensures zero LED leakage current and complete system isolation when EN/UVLO is low - critical for safety-critical automotive lighting. |
| Integrated current monitor outputs | ISMON (10× VISP–ISN) and IVINMON (20× VIVINP–IVINN) provide real-time, calibrated telemetry for system-level diagnostics and closed-loop power management. |
| Robust fault protection suite | Detects and latches on open LED (via FB > 1.15V), shorted LED (FB < 400mV), input overvoltage (OVLO > 3V), and thermal overload - with dedicated open-drain flag pins. |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
|
Use Scenario: Adaptive front-lighting system (AFS) requiring dynamic beam shaping, high-luminance output, and compliance with ECE R112 and SAE J2346. IC Role / Device Role / Timing Role: Primary LED current controller managing 33.3V/3A (100W) LED strings with seamless transition between low-beam (buck), high-beam (boost), and cornering (buck-boost) modes. Use Value: Eliminates need for separate buck and boost converters, reduces BOM count by 30%, and maintains ±6% current accuracy across –40°C to 150°C ambient for consistent photometric performance. |
Use Scenario: 150W+ warehouse lighting using series-connected COB LEDs powered from 48V DC microgrids with strict thermal derating requirements. IC Role / Device Role / Timing Role: Constant-current regulator driving 52V LED strings from 4.7–60V input, supporting analog dimming via CTRL and synchronized PWM dimming across multiple fixtures. Use Value: Achieves 98.5% peak efficiency at full load, reducing heatsink mass by 40% versus legacy solutions, while integrated ISMON/IVINMON enables predictive maintenance via cloud telemetry. |
| Battery-Powered Emergency Lighting | UV-C Disinfection Systems |
|
Use Scenario: Portable emergency egress lighting with LiFePO₄ battery (24–36V) powering 36V UV-A LED arrays requiring stable current despite deep discharge. IC Role / Device Role / Timing Role: Wide-input buck-boost controller maintaining 3A LED current across battery voltage sag from 36V to 24V, with programmable soft-start to avoid inrush tripping protection circuits. Use Value: Extends runtime by 18% versus fixed-buck designs due to efficient operation down to 24V, and built-in open/short LED fault detection prevents false alarms during battery-swapping events. |
Use Scenario: Pulsed UV-C germicidal modules using 30–40V LED stacks driven from 24V industrial power rails with strict duty-cycle control to manage LED junction temperature. IC Role / Device Role / Timing Role: Precision current controller implementing True Color PWM™ dimming at 1–10kHz to deliver calibrated UV dose per pulse while avoiding LED thermal runaway. Use Value: Enables ±1% pulse-to-pulse current repeatability across temperature, ensuring validated microbial kill rates; VC pin allows real-time current modulation synchronized to motion sensors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LED driver controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8391EFE#PBF | Successor IC with improved 99% efficiency, lower IQ (2.5mA vs 4mA), enhanced spread-spectrum EMI reduction, and integrated boost diode driver. | Targets new designs requiring higher efficiency, tighter EMI compliance, and simplified layout; not drop-in compatible due to different pinout and CTRL/SS behavior. | Select LT8391EFE#PBF for greenfield automotive or industrial LED projects where lifecycle support and latest feature set are prioritized. |
| LTC3789EGN#PBF | 4-switch buck-boost controller without integrated LED-specific features: no True Color PWM™, no OPENLED/SHORTLED flags, no ISMON/IVINMON outputs. | General-purpose DC/DC conversion only; requires external circuitry for LED current sensing, fault signaling, and dimming interface. | Choose LTC3789EGN#PBF only when driving non-LED loads (e.g., laser diodes, sensors) or when full custom LED system architecture is already implemented. |
Compared with LT8391EFE#PBF, the LT3791HFE#PBF offers proven field reliability and broader temperature qualification (–40°C to 150°C), while LTC3789EGN#PBF provides greater flexibility for non-LED applications but demands additional external components to match LT3791HFE#PBF's integrated LED protection and monitoring capabilities.
Availability
LT3791HFE#PBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and battery-powered emergency lighting requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3791HFE#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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, power management, and industrial automation.
The LT3791 product line delivers robust, high-efficiency LED driver controllers optimized for demanding automotive, industrial, and portable lighting applications where wide input/output voltage range and seamless buck-boost-buck-boost transitions are essential.
FAQ
What is the maximum LED string voltage supported by the LT3791HFE#PBF?
The LT3791HFE#PBF supports LED string voltages up to 52V, as specified in its absolute maximum ratings and confirmed by the "Wide VOUT Range: 0V to 60V (52V LED)" feature listing. This rating is maintained across the full –40°C to 150°C operating junction temperature range, making LT3791HFE#PBF suitable for high-voltage LED arrays in automotive and industrial environments where thermal stress is significant.
Does the LT3791HFE#PBF support synchronization with external clock sources?
Yes, the LT3791HFE#PBF supports external clock synchronization via its SYNC pin (Pin 34), which accepts input frequencies from 200kHz to 700kHz. The internal 90kΩ pull-down resistor simplifies interface design, and the rising edge of the external clock aligns with the internal oscillator's rising edge. This capability enables precise phase alignment of multiple LT3791HFE#PBF controllers in high-power LED systems, reducing input ripple and EMI.
How does the LT3791HFE#PBF handle open or shorted LED faults?
The LT3791HFE#PBF detects open LED conditions when FB exceeds 1.15V (rising threshold) while V(ISP–ISN) remains below 10mV, asserting the OPENLED pin. For shorted LED faults, it monitors FB falling below 400mV and asserts SHORTLED. Both pins are open-drain and require external pull-ups. During either fault, the SS pin can be configured to latch off the controller using a 500kΩ resistor to VREF, ensuring fail-safe operation in LT3791HFE#PBF-based lighting systems.
What is the purpose of the CTRL pin on the LT3791HFE#PBF?
The CTRL pin (Pin 1) on the LT3791HFE#PBF adjusts the LED current sense threshold from 6.5mV to 100mV in analog dimming applications. Its transfer function is linear below 1.1V (V(ISP–ISN) = 0.1 × (VCTRL – 200mV)), saturates at full scale above 1.3V, and transitions smoothly between. Connecting CTRL to VREF sets the default 100mV threshold. This pin enables precise, temperature-compensated current regulation without external DACs, a core capability of the LT3791HFE#PBF.
Can the LT3791HFE#PBF operate with input voltages below 5V?
No, the LT3791HFE#PBF has a minimum input voltage specification of 4.7V, as stated in its Electrical Characteristics table under "VIN Operating Voltage". Operation below this threshold risks improper startup, unstable regulation, or failure to meet guaranteed performance specifications across temperature. For sub-5V LED driver applications, alternative controllers such as the LT3965 or LT3762 should be evaluated instead of the LT3791HFE#PBF.
LT3791HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- True Color PWM™
- Package/Case:
- 38-TFSOP (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):
- 4.7V
- Voltage - Supply (Max):
- 60V
- Voltage - Output:
- 0V ~ 60V
- Current - Output / Channel:
- -
- Frequency:
- 200 ~ 700kHz
- Dimming:
- Analog, PWM
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT3791HFE#PBF FAQ
1.How can I place an order for LT3791HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3791HFE#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 LT3791HFE#PBF reliable?
The price and inventory of LT3791HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3791HFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3791HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3791HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3791HFE#PBF?
LT3791HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3791HFE#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 LT3791HFE#PBF?
For technical support, including LT3791HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3791HFE#PBF requirements.
6.How does Aetrix verify that LT3791HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3791HFE#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 LT3791HFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3791HFE#PBF?
All LT3791HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3791HFE#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 LT3791HFE#PBF part is unused and in its original packaging.
Return procedure for LT3791HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3791HFE#PBF Tags
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BCR402RE6327HTSA1
Infineon Technologies
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Infineon Technologies
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Infineon Technologies
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Power Integrations
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Microchip Technology
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