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Analog Devices Inc. LT3791HFE#TRPBF
- Part No.:
- LT3791HFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3791HFE#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,041
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Product details
Overview
LT3791HFE#TRPBF from Analog Devices is a 60V synchronous 4-switch buck-boost LED driver controller designed for constant-current regulation of LED strings up to 52V with input voltages from 4.7V to 60V. It operates across buck, boost, and buck-boost regions with seamless transitions, supports True Color PWM™ and analog dimming, and delivers up to 98.5% efficiency in 100W (33.3V/3A) configurations - ideal for automotive headlamps and industrial lighting.
For engineers reviewing the LT3791HFE#TRPBF datasheet, LT3791HFE#TRPBF pinout, LT3791HFE#TRPBF application, or LT3791HFE#TRPBF equivalent, key selection criteria include its –40°C to 150°C junction temperature rating, 38-lead TSSOP package with exposed pad, 200kHz–700kHz adjustable switching frequency, ±6% LED current accuracy over 0V–52V LED voltage range, and integrated open/shorted LED fault protection.
Technical Context
The LT3791HFE#TRPBF implements a constant-frequency, forced-continuous conduction mode architecture with dual current-sense amplifiers (input and output), independent regulation loops for LED current and input current, and a VC pin that arbitrates between feedback paths to enforce priority-based control. Its 4-switch single-inductor topology eliminates top MOSFET refresh cycles in pure buck or boost operation.
Operation spans three distinct regions-buck (VIN > VOUT), boost (VIN < VOUT), and buck-boost (VIN ≈ VOUT)-with automatic, glitch-free transitions governed by duty-cycle thresholds and internal logic. Fault detection includes open LED (FB > 1.15V + V(ISP-ISN) < 10mV) and shorted LED (FB < 400mV), each asserting dedicated open-drain outputs (OPENLED/SHORTLED).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.7V to 60V - supports wide-range battery and automotive supply rails without external pre-regulation. |
| Output Voltage Capability | 0V to 60V (52V LED string max) - enables direct drive of high-voltage LED arrays without intermediate conversion stages. |
| LED Current Accuracy | ±6% over 0V ≤ VLED < 52V - ensures consistent luminance across varying forward voltage and temperature conditions. |
| Switching Frequency Range | 200kHz to 700kHz - adjustable via RT resistor or external SYNC signal for EMI optimization and magnetics sizing. |
| Junction Temperature Range | –40°C to 150°C - qualified for under-hood automotive and high-ambient industrial environments. |
| Efficiency | Up to 98.5% at 100W (33.3V/3A) - minimizes thermal load and improves system power density in space-constrained designs. |
| Package | 38-Lead TSSOP with exposed pad - provides low thermal resistance (θJA = 28°C/W) and robust PCB heat sinking capability. |
Pinout & Package
LT3791HFE#TRPBF is housed in a 38-lead plastic TSSOP package with exposed pad (Pin 39), which must be soldered to the PCB ground plane for thermal and electrical integrity. The package supports surface-mount assembly and meets JEDEC MS-013 standards.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CTRL (1) | Analog dimming threshold adjust | Sets LED current sense threshold as 1/10 × (VCTRL – 200mV); 0.2V–1.1V linear range enables precise analog brightness control. |
| SS (2) | Soft-start and fault timer | Controls startup inrush current via external capacitor; doubles as latch-off timer during OPENLED/SHORTLED faults. |
| PWM (3) | Digital dimming enable | Active-low signal halts switching, disconnects VC, and drives PWMOUT - enables high-frequency True Color PWM™ dimming. |
| OPENLED (4) | Open-circuit fault indicator | Open-drain output asserted when FB > 1.15V and V(ISP-ISN) < 10mV - triggers external circuitry for LED string monitoring. |
| SHORTLED (5) | Short-circuit fault indicator | Open-drain output asserted when FB < 400mV - enables fast shutdown and diagnostic response to LED short events. |
| VREF (6) | 2.00V reference source | Stable 2V output (±2%) supplies bias for CTRL divider and external compensation; capable of sourcing 200µA. |
| ISMON (7) | LED current monitor output | 10× scaled replica of V(ISP-ISN); 1V output at 100mV sense voltage - simplifies current measurement and feedback loop analysis. |
| IVINMON (8) | Input current monitor output | 20× scaled replica of V(IVINP-IVINN); 1V output at 50mV sense voltage - supports input power limiting and system-level energy management. |
| EN/UVLO (9) | Enable and undervoltage lockout | 1.2V falling threshold with 15mV hysteresis; sub-µA bias above threshold enables ultra-low quiescent operation. |
| IVINP/IVINN (10,11) | Input current sense inputs | Differential pair with 50mV trip threshold and 2.12mS transconductance - enables accurate input current regulation and foldback. |
| VIN (12) | Main power input | Accepts 4.7V–60V supply; requires local ceramic bypass to PGND to stabilize INTVCC and reduce noise coupling. |
| INTVCC (13) | Internal 5V LDO output | Regulated 5.0V ±0.2V supply for gate drivers and logic; requires ≥4.7µF ceramic capacitor to PGND for stability. |
| TG1/BST1/SW1 (14–16) | Buck-side high-side switch interface | TG1 drives M1 top N-MOSFET; BST1 supplies floating gate drive; SW1 connects to inductor node - forms buck leg with M1/M2. |
| PGND (17,20) | Power ground return | Low-impedance path for bottom MOSFET sources and high-current return; must be connected near MOSFET source pads. |
| BG1/BG2 (18,19) | Buck/boost low-side gate drivers | Drive M2 and M3 bottom N-MOSFETs from GND to INTVCC; 3Ω pull-up / 1.2Ω pull-down typical RDS(on). |
| SW2/BST2/TG2 (21–22,24) | Boost-side high-side switch interface | TG2 drives M4 top N-MOSFET; BST2 supplies floating gate drive; SW2 connects to output node - forms boost leg with M3/M4. |
| ISP/ISN (25–26) | LED current sense inputs | Differential pair with 100mV default trip threshold (adjustable via CTRL); 890µS transconductance enables stable current regulation. |
| SNSP/SNSN (27–28) | Current comparator inputs | Compare VC-derived threshold against sensed inductor current slope; support buck-boost boundary detection and cycle-by-cycle current limiting. |
| SGND (30,39) | Signal ground reference | Reference for all small-signal pins (FB, CTRL, SS, etc.); must connect to PGND at single point to avoid ground loops. |
| PWMOUT (31) | Buffered PWM output | INTVCC-referenced open-drain output synchronized with PWM pin - drives external MOSFET for LED disconnect or auxiliary control. |
| CLKOUT (33) | Master clock output | Provides in-phase oscillator signal at fSW - enables synchronization of multiple LT3791HFE#TRPBF controllers for parallel LED string operation. |
| SYNC (34) | External clock input | Accepts 200kHz–700kHz external clock; rising-edge synchronized to internal oscillator - supports multi-phase interleaving and EMI reduction. |
| RT (35) | Frequency set resistor | Resistor to SGND sets switching frequency: 147kΩ → 200kHz, 59.0kΩ → 400kHz, 29.1kΩ → 700kHz. |
| VC (36) | Error amplifier output & current threshold | 0.7V–1.9V control voltage that sets current limit; arbitrates between LED, input, and FB loops to enforce operational priority. |
| FB (37) | Output voltage feedback | Regulates to 1.20V ±12mV; detects open/short LED faults; connects to LED cathode or output capacitor divider for CV protection. |
| OVLO (38) | Overvoltage lockout input | Shuts down converter if >3.0V applied; prevents damage from output overvoltage events such as LED string disconnection. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor architecture | Enables VIN above, below, or equal to VOUT without topology change - eliminates need for separate buck/boost ICs or complex power sequencing. |
| True Color PWM™ dimming | Preserves LED color fidelity at any dimming level by maintaining full forward current during on-time - critical for automotive and architectural lighting. |
| No top MOSFET refresh in buck/boost | Removes unnecessary switching losses in pure buck or boost modes - improves efficiency and reduces gate driver stress versus conventional 4-switch controllers. |
| VOUT disconnected from VIN during shutdown | Prevents backfeed from output to input rail when disabled - enhances system safety and simplifies power domain isolation in multi-rail systems. |
| Integrated open/short LED fault protection | Dedicated OPENLED and SHORTLED pins provide immediate, latchable fault signaling - enables fail-safe behavior without external comparators or microcontroller polling. |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) requiring dynamic beam shaping and high-lumen output across 9–16V battery range with cold-crank tolerance. IC Role / Device Role / Timing Role: Primary LED current controller managing 33.3V/3A LED string while regulating input current to prevent alternator overload. Use Value: Seamless buck-boost transition maintains constant LED brightness during engine start (VIN dip to 6V) and overvoltage events (VIN surge to 18V), supported by 150°C junction rating. | Use Scenario: 100W+ high-bay fixture powered from 24VDC industrial bus, driving 48V LED string with analog dimming for daylight harvesting. IC Role / Device Role / Timing Role: Constant-current buck-boost controller with IVINMON feedback enabling input current limiting to match upstream DC-DC converter capacity. Use Value: 98.5% peak efficiency reduces thermal load in enclosed fixtures; ±6% LED current accuracy ensures uniform illumination across 100+ units in warehouse deployment. |
| Battery-Powered Emergency Lighting | UV-C Disinfection Systems |
Use Scenario: Portable emergency light using 12V LiFePO₄ battery (10–14.6V) to drive 36V UV-A LED array with PWM dimming for runtime extension. IC Role / Device Role / Timing Role: Wide-input buck-boost LED driver supporting True Color PWM™ dimming at 1kHz to eliminate visible flicker during evacuation scenarios. Use Value: 200kHz–700kHz frequency adjustment allows EMI filtering optimized for portable enclosure; shutdown IQ < 1µA preserves battery life during standby. | Use Scenario: Pulsed UV-C disinfection module requiring precise 275nm LED current control (350mA–700mA) with rapid on/off cycling and thermal derating. IC Role / Device Role / Timing Role: High-accuracy current regulator with ISP/ISN sensing and CTRL-adjustable threshold enabling programmable pulse amplitude and duty cycle. Use Value: ±6% LED current accuracy over 0–52V ensures consistent germicidal dose delivery; 150°C rating accommodates heatsink-limited thermal design. |
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#TRPBF | Successor IC with improved efficiency (up to 99%), lower IQ (2.5mA vs 4mA), enhanced fault diagnostics, and integrated spread-spectrum modulation. | Designed for new designs requiring higher reliability, lower EMI, and extended lifetime - not drop-in compatible due to different pinout and CTRL/SS behavior. | Select LT8391EFE#TRPBF for greenfield projects where performance and longevity outweigh legacy compatibility needs. |
| LTC3789EGN#TRPBF | 4-switch buck-boost controller with 40V max input/output, no integrated LED-specific features (no OPENLED/SHORTLED, no ISMON), and fixed 300kHz–400kHz frequency. | General-purpose power conversion only; lacks LED protection, dimming interfaces, and current-monitor outputs required for lighting applications. | Choose LTC3789EGN#TRPBF only for non-LED DC-DC conversion where cost and simplicity are prioritized over lighting-specific functionality. |
Compared with LT8391EFE#TRPBF and LTC3789EGN#TRPBF, the LT3791HFE#TRPBF offers unique LED-focused features - including True Color PWM™, dedicated fault pins, and LED current monitor outputs - making it irreplaceable in lighting designs requiring certified safety, dimming fidelity, and system-level diagnostics, despite its older architecture.
Availability
LT3791HFE#TRPBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and battery-powered emergency lighting requiring stable component supply, extended temperature operation, and long-term production continuity.
Supply support for LT3791HFE#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 technologies, serving industrial, automotive, communications, and healthcare markets.
The LT3791 product line was developed specifically for high-efficiency, wide-input-range LED driver applications demanding seamless buck-boost operation, precise current regulation, and robust fault handling in harsh environments.
FAQ
What is the maximum operating junction temperature for the LT3791HFE#TRPBF?
The LT3791HFE#TRPBF is rated for a maximum operating junction temperature of 150°C, as confirmed by its H-grade qualification and Absolute Maximum Ratings table. This specification enables reliable operation in under-hood automotive and high-ambient industrial environments where thermal management is constrained. The LT3791HFE#TRPBF achieves this rating through process and packaging enhancements beyond the standard E/I grades.
Does the LT3791HFE#TRPBF support both analog and PWM dimming simultaneously?
Yes, the LT3791HFE#TRPBF supports simultaneous analog and PWM dimming: analog dimming is implemented via the CTRL pin to adjust the LED current sense threshold, while True Color PWM™ dimming uses the PWM pin to modulate switching without altering current magnitude. The LT3791HFE#TRPBF maintains color consistency across dimming levels by preserving full LED forward current during PWM on-time, unlike conventional PWM-only drivers.
How does the LT3791HFE#TRPBF handle open or shorted LED conditions?
The LT3791HFE#TRPBF detects open LED conditions when FB exceeds 1.15V while V(ISP-ISN) falls below 10mV, asserting the OPENLED pin. Shorted LED conditions trigger when FB drops below 400mV, asserting SHORTLED. Both pins are open-drain and require external pull-ups. The LT3791HFE#TRPBF also uses the SS pin as a fault timer - a 500kΩ resistor from SS to VREF latches off the device permanently upon fault detection.
Can the LT3791HFE#TRPBF synchronize with other controllers?
Yes, the LT3791HFE#TRPBF supports external synchronization via the SYNC pin, accepting 200kHz–700kHz clock signals with rising-edge alignment. It also provides a phase-matched CLKOUT signal at the same frequency, enabling precise interleaving of multiple LT3791HFE#TRPBF controllers to reduce input/output ripple and improve thermal distribution in high-power LED systems.
What is the purpose of the exposed pad (Pin 39) on the LT3791HFE#TRPBF package?
The exposed pad (Pin 39) on the LT3791HFE#TRPBF is designated SGND and must be soldered directly to the PCB ground plane. It serves dual purposes: lowering thermal resistance (θJA = 28°C/W) to dissipate heat from the IC's power circuits, and providing a low-impedance signal ground reference for sensitive analog pins like FB, CTRL, and SS. Failure to solder this pad compromises both thermal performance and regulation accuracy.
LT3791HFE#TRPBF 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:
- 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):
- 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#TRPBF FAQ
1.How can I place an order for LT3791HFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3791HFE#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 LT3791HFE#TRPBF reliable?
The price and inventory of LT3791HFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3791HFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3791HFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3791HFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3791HFE#TRPBF?
LT3791HFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3791HFE#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 LT3791HFE#TRPBF?
For technical support, including LT3791HFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3791HFE#TRPBF requirements.
6.How does Aetrix verify that LT3791HFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3791HFE#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 LT3791HFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3791HFE#TRPBF?
All LT3791HFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3791HFE#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 LT3791HFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3791HFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3791HFE#TRPBF Tags
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