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Analog Devices Inc. LT3791EFE#TRPBF
- Part No.:
- LT3791EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3791EFE#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,374
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Product details
Overview
LT3791EFE#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 supports seamless transitions between buck, boost, and buck-boost modes, delivers ±6% LED current accuracy across 0–52V LED voltage range, and operates at adjustable switching frequencies from 200kHz to 700kHz. It is deployed in automotive headlamps and industrial lighting systems requiring wide VIN/VOUT flexibility.
For engineers reviewing the LT3791EFE#TRPBF datasheet, LT3791EFE#TRPBF pinout, LT3791EFE#TRPBF application, or LT3791EFE#TRPBF equivalent, key selection criteria include its 38-lead TSSOP package with exposed pad, dual current-sense architecture (ISP/ISN and IVINP/IVINN), True Color PWM™ dimming support, open/short LED fault protection, and compatibility with high-power 100W+ LED drivers.
Technical Context
The LT3791EFE#TRPBF implements a constant-frequency, forced-continuous conduction mode (FCCM) control architecture 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 topology eliminates top MOSFET refresh cycles in pure buck or boost operation, reducing switching losses and enabling >98.5% peak efficiency at 33.3V/3A.
Internal gate drivers support N-channel MOSFETs with TG1/TG2 pull-up resistance of 2.6Ω and BG1/BG2 pull-down resistance of 1.2Ω at VINTVCC = 5V. The VC pin serves as both error amplifier output and current threshold control point (0.7V–1.9V), while dedicated SNSP/SNSN pins provide programmable current sense comparator offsets for buck (–56mV to –39mV) and boost (42mV to 60mV) regions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.7V to 60V - supports 12V/24V/48V automotive and industrial rails without external pre-regulation. |
| Output Voltage Range | 0V to 60V (52V LED max) - enables direct drive of long LED strings without intermediate converters. |
| LED Current Accuracy | ±6% over 0V ≤ VLED < 52V - ensures consistent luminance across temperature and line/load variations. |
| Switching Frequency | 200kHz to 700kHz (RT-programmable) - balances EMI, efficiency, and inductor size for compact designs. |
| Package | 38-Lead TSSOP with exposed pad - provides thermal performance suitable for 100W+ LED driver applications. |
| Fault Protection | Open LED (FB > 1.15V), shorted LED (FB < 400mV), OVLO (>3V), thermal shutdown - ensures robust system-level reliability. |
| Dimming Interface | True Color PWM™ + analog dimming via CTRL pin - preserves color fidelity and enables smooth 1000:1 dimming ratio. |
Pinout & Package
LT3791EFE#TRPBF is housed in a 38-lead plastic TSSOP package with exposed pad (Pin 39), which must be soldered to PCB ground 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 linearly from 200mV to 1.1V; 100mV default when tied to VREF. |
| SS (2) | Soft-start/fault timer | Controls startup inrush current; latches off during OPENLED/SHORTLED faults when pulled to VREF via 500kΩ. |
| PWM (3) | Digital dimming enable | Active-low signal halts switching and disconnects VC; internal 100kΩ pull-down allows tie-to-INTVCC if unused. |
| OPENLED (4) | Open-circuit fault indicator | Open-drain output asserting when FB > 1.15V and V(ISP-ISN) < 10mV - requires external pull-up. |
| SHORTLED (5) | Short-circuit fault indicator | Open-drain output asserting when FB < 400mV - requires external pull-up. |
| VREF (6) | 2.00V reference output | Stable 2V source (±2%) for biasing CTRL, ISMON, IVINMON; supplies up to 200µA. |
| ISMON (7) | LED current monitor | 10× scaled V(ISP-ISN); outputs 1V at 100mV sense voltage - enables real-time current telemetry. |
| IVINMON (8) | Input current monitor | 20× scaled V(IVINP-IVINN); outputs 1V at 50mV sense voltage - supports input power limiting. |
| EN/UVLO (9) | Enable/undervoltage lockout | 1.2V falling threshold with 15mV hysteresis; sub-µA bias above threshold, 3µA pull-down below. |
| IVINP/IVINN (10,11) | Input current sense inputs | Differential pair with 50mV trip threshold; common-mode range 3V–60V - enables accurate input current regulation. |
| VIN (12) | Main power input | Accepts 4.7V–60V; bypass to PGND with ≥4.7µF ceramic capacitor for stability. |
| INTVCC (13) | Internal 5V LDO output | Regulated 5.0V ±2% supply for logic and gate drivers; dropout <350mV at –10mA. |
| TG1/BST1/SW1 (14–16) | Buck-side high-side driver chain | TG1 drives M1 top FET; BST1 bootstraps TG1; SW1 connects to inductor node - forms buck path. |
| PGND (17,20) | Power ground return | Low-impedance connection point for bottom FET sources and bulk capacitors - critical for noise immunity. |
| BG1/BG2 (18,19) | Buck/boost low-side gate drivers | Drive M2/M3 bottom FETs from GND to INTVCC; 1.2Ω pull-down resistance ensures fast turn-off. |
| SW2/BST2/TG2 (21,22,24) | Boost-side high-side driver chain | TG2 drives M4 top FET; BST2 bootstraps TG2; SW2 connects to output node - forms boost path. |
| ISP/ISN (25,26) | LED current sense inputs | Differential pair with 100mV default trip; common-mode range 0V–60V - supports high-side or low-side sensing. |
| SNSP/SNSN (27,28) | Current comparator inputs | Set buck/boost current thresholds via VC-controlled offsets; buck range –56mV to –39mV, boost 42mV to 60mV. |
| TEST1 (29)/SGND (30) | Test/signal ground | TEST1 must connect to SGND; SGND is separate from PGND - star-grounding required for precision feedback. |
| PWMOUT (31) | Buffered PWM output | INTVCC-referenced gate drive for external LED disconnect FET; 5–10Ω on-resistance supports fast switching. |
| TEST2 (32) | Factory test pin | Must connect to INTVCC (Pin 13) for normal operation - floating or incorrect connection disables device. |
| CLKOUT/SYNC/RT (33–35) | Timing interface | CLKOUT mirrors oscillator; SYNC accepts 200–700kHz external clock; RT sets frequency via resistor to GND. |
| VC (36) | Error amplifier output | 0.7V–1.9V control voltage setting current threshold; also compensation node for loop stability. |
| FB (37) | Output voltage feedback | Regulates to 1.2V ±1.5%; triggers OPENLED/SHORTLED faults; used for CV mode or LED overvoltage protection. |
| OVLO (38) | Overvoltage lockout | Shuts down converter when >3.0V applied; 75mV hysteresis prevents oscillation near threshold. |
| NC (23) | No-connect | Unbonded pin - must remain unconnected per datasheet. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor architecture | Enables VIN above, below, or equal to VOUT without topology change - eliminates need for multiple DC/DC stages. |
| No top MOSFET refresh cycle | Reduces switching loss and EMI in buck/boost modes - improves efficiency by ~1–2% versus conventional controllers. |
| VOUT disconnected from VIN during shutdown | Prevents backfeed into input rail - essential for battery-powered systems and safety-critical lighting. |
| True Color PWM™ dimming | Maintains LED chromaticity across full dimming range - meets automotive headlamp color consistency standards. |
| Integrated current monitor outputs | ISMON and IVINMON provide isolated, scaled analog signals - simplifies system telemetry and diagnostics without extra ICs. |
| Seamless buck-boost transition | Eliminates output voltage discontinuity or current glitch when VIN crosses VOUT - critical for stable illumination in varying input conditions. |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive front-lighting system (AFS) with dynamic beam shaping and daytime running lamp (DRL) integration. IC Role / Device Role / Timing Role: Primary LED current controller regulating 30–50V LED arrays from 9–16V battery with cold-crank tolerance down to 4.7V. Use Value: Maintains ±6% current accuracy across –40°C to 125°C junction temperature, ensuring consistent photometric output under extreme ambient conditions. | Use Scenario: 100W+ high-efficiency LED fixture for warehouse or factory floor illumination powered from 24–48V DC distribution bus. IC Role / Device Role / Timing Role: Constant-current buck-boost controller driving 36V/2.8A LED string with input voltage variation from 24V to 56V due to cable drop and load transients. Use Value: Delivers >98.5% peak efficiency at 33.3V/3A, reducing thermal load and enabling passive cooling in enclosed fixtures. |
| Emergency Vehicle Lighting | Portable Battery-Powered Searchlights |
Use Scenario: Flashing red/blue LED beacon with rapid on/off cycling and high peak brightness requirements. IC Role / Device Role / Timing Role: High-speed PWM dimming controller using True Color PWM™ to preserve spectral output during 100Hz–2kHz strobing. Use Value: Achieves 1000:1 dimming ratio without color shift, meeting SAE J575 and ECE R10 photometric compliance. | Use Scenario: Handheld searchlight operating from 12V Li-ion battery pack with voltage sag from 12.6V (fully charged) to 9V (discharged). IC Role / Device Role / Timing Role: Wide-input buck-boost LED driver maintaining constant 3A output current across entire battery discharge curve. Use Value: Eliminates need for battery voltage pre-regulation, extending runtime by 12% versus fixed-buck solutions limited to VIN > VOUT. |
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), integrated spread-spectrum modulation, and enhanced fault diagnostics. | Designed for new designs requiring higher power density and stricter EMI compliance; not pin-compatible with LT3791EFE#TRPBF. | Select LT8391EFE#TRPBF for greenfield projects needing best-in-class performance; retain LT3791EFE#TRPBF for legacy design continuity and cost-sensitive volume production. |
| LTC3789EGN#TRPBF | 4-switch buck-boost controller with identical topology but narrower input range (4V–36V), no integrated LED-specific features (e.g., OPENLED/SHORTLED pins), and no True Color PWM™. | General-purpose DC/DC conversion only; requires external circuitry for LED current regulation and fault handling. | Choose LTC3789EGN#TRPBF only when driving non-LED loads or when full LED feature set is unnecessary; LT3791EFE#TRPBF remains superior for dedicated LED applications. |
Compared with LT8391EFE#TRPBF and LTC3789EGN#TRPBF, the LT3791EFE#TRPBF offers purpose-built LED functionality-including dedicated fault pins, analog/PWM dimming interfaces, and ±6% current accuracy-making it optimal for cost-constrained, high-reliability LED lighting where feature completeness outweighs marginal efficiency gains.
Availability
LT3791EFE#TRPBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and portable battery-powered searchlights requiring stable component supply across extended temperature ranges (–40°C to 125°C).
Supply support for LT3791EFE#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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, industrial automation, and automotive systems.
The LT3791 product line was developed specifically for high-efficiency, wide-input-range LED driver applications demanding seamless buck-boost operation, robust fault protection, and industry-leading current regulation accuracy in harsh environments.
FAQ
What is the maximum LED string voltage supported by the LT3791EFE#TRPBF?
The LT3791EFE#TRPBF 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 enables direct drive of multi-series white LED arrays commonly used in automotive and industrial lighting, with built-in open LED protection triggering when FB exceeds 1.15V.
Does the LT3791EFE#TRPBF require external Schottky diodes for synchronous rectification?
No, the LT3791EFE#TRPBF does not require external Schottky diodes across synchronous switches M2 or M4. Its gate drive timing and dead-time control eliminate shoot-through risk. However, adding Schottky diodes can improve peak efficiency by 1–2% at 500kHz by reducing body-diode conduction loss during dead time - an optional optimization, not a requirement.
How does the LT3791EFE#TRPBF handle input voltage fluctuations during cold-crank conditions in automotive applications?
The LT3791EFE#TRPBF maintains regulation down to 4.7V input, covering automotive cold-crank events (typically 4.5–6V). Its EN/UVLO pin has a precise 1.2V falling threshold with 15mV hysteresis, and internal 3µA pull-down ensures clean restart after undervoltage recovery. Combined with 60V absolute maximum VIN rating, it withstands load-dump transients without external protection.
Can the LT3791EFE#TRPBF be synchronized to an external clock source?
Yes, the LT3791EFE#TRPBF supports external synchronization via its SYNC pin (Pin 34), which accepts a 200kHz–700kHz square wave. The internal 90kΩ pull-down resistor allows direct connection to a CMOS clock source. Synchronization eliminates beat frequencies in multi-phase or multi-lamp systems and reduces EMI by aligning switching edges across multiple LT3791EFE#TRPBF devices.
What thermal management considerations apply to the LT3791EFE#TRPBF in 100W LED driver designs?
The LT3791EFE#TRPBF's 38-lead TSSOP package has θJA = 28°C/W. For 100W operation, thermal design must ensure junction temperature stays ≤125°C. This requires soldering the exposed pad (Pin 39) directly to a minimum 200mm² copper pour on the PCB, using ≥4 thermal vias, and maintaining ambient temperature ≤75°C. Derating is necessary above 100°C ambient per datasheet Note 2.
LT3791EFE#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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT3791EFE#TRPBF FAQ
1.How can I place an order for LT3791EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3791EFE#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 LT3791EFE#TRPBF reliable?
The price and inventory of LT3791EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3791EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3791EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3791EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3791EFE#TRPBF?
LT3791EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3791EFE#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 LT3791EFE#TRPBF?
For technical support, including LT3791EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3791EFE#TRPBF requirements.
6.How does Aetrix verify that LT3791EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3791EFE#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 LT3791EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3791EFE#TRPBF?
All LT3791EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3791EFE#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 LT3791EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3791EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3791EFE#TRPBF Tags
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BCR402RE6327HTSA1
Infineon Technologies
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BCR430UXTSA2
Infineon Technologies
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BCR420UE6433HTMA1
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Infineon Technologies
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LYT1604D-TL
Power Integrations
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Microchip Technology
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Microchip Technology
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Diodes Incorporated
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Diodes Incorporated
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Diodes Incorporated
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