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Analog Devices Inc. LT3791MPFE#TRPBF
- Part No.:
- LT3791MPFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3791MPFE#TRPBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,827
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Product details
Overview
LT3791MPFE#TRPBF from Analog Devices is a 60V synchronous 4-switch buck-boost LED driver controller designed for automotive headlamps and industrial lighting systems. It regulates LED current up to 52V with input voltage ranging from 4.7V to 60V, supports constant-frequency forced-continuous conduction mode (200–700 kHz), delivers ±6% LED current accuracy across 0–52V LED range, and features True Color PWM™ dimming and open/shorted LED fault protection.
For engineers reviewing the LT3791MPFE#TRPBF datasheet, LT3791MPFE#TRPBF pinout, LT3791MPFE#TRPBF application, or LT3791MPFE#TRPBF equivalent, key selection considerations include its –55°C to 150°C operating junction temperature rating, 38-lead TSSOP package with exposed pad, 4-switch single-inductor architecture enabling VIN above/below/equal to VOUT, and integrated input/output current monitoring with dedicated ISMON and IVINMON outputs.
Technical Context
The LT3791MPFE#TRPBF implements a current-mode 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 topology eliminates top MOSFET refresh cycles in pure buck or boost modes, enabling seamless transitions between buck, buck-boost, and boost regions without discontinuity or instability.
It integrates dual gate drivers (TG1/BG1 and TG2/BG2) with specified on-resistances (2.6Ω pull-up / 1.7Ω pull-down for TGs; 3Ω/1.2Ω for BGs), internal 5V INTVCC regulator (4.8–5.2V, 67mA limit), and precision analog comparators for open LED (1.15V FB threshold) and short LED (400mV FB threshold) detection-all qualified for extended temperature operation up to 150°C junction.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.7V to 60V - supports wide automotive battery transients and industrial DC bus variations without external pre-regulation. |
| Output Voltage Capability | 0V to 60V (52V LED string max) - enables direct drive of multi-LED strings without intermediate conversion stages. |
| LED Current Accuracy | ±6% over 0V ≤ VLED < 52V - ensures consistent luminance across temperature and line/load conditions in safety-critical lighting. |
| Switching Frequency Range | 200kHz to 700kHz - allows EMI optimization and compact magnetics design while maintaining forced CCM stability. |
| Junction Temperature Range | –55°C to 150°C - qualified for under-hood automotive, high-ambient industrial, and aerospace-grade thermal environments. |
| Package | 38-lead TSSOP with exposed pad - provides low thermal resistance (θJA = 28°C/W) and robust PCB solder joint reliability. |
| Dimming Interface | True Color PWM™ + analog dimming via CTRL pin - preserves color fidelity at low duty cycles and enables smooth brightness control. |
Pinout & Package
LT3791MPFE#TRPBF is housed in a 38-lead plastic TSSOP (FE package) with exposed pad (Pin 39), which must be soldered to PCB ground plane for thermal and electrical integrity. The package measures 9.7mm × 4.4mm × 1.1mm (max height) and supports lead-free reflow assembly.
| 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; forces shutdown below 175mV. |
| SS (2) | Soft-start & fault timer | Controls startup inrush current via external capacitor; latches off during OPENLED/SHORTLED faults when pulled to VREF via 500kΩ. |
| PWM (3) | Digital dimming enable | Active-low signal halts switching, disconnects VC, and drives PWMOUT; includes internal 100kΩ pull-down. |
| OPENLED (4) | Open-circuit LED fault indicator | Open-drain output asserting when FB > 1.15V and V(ISP−ISN) < 10mV; requires external pull-up resistor. |
| SHORTLED (5) | Short-circuit LED fault indicator | Open-drain output asserting when FB < 400mV; requires external pull-up resistor; enables fail-safe load disconnect. |
| VREF (6) | 2.00V reference output | Stable 2V reference (±2%) sourcing up to 200µA; used for CTRL biasing, temperature compensation, or external scaling. |
| ISMON (7) | LED current monitor output | 10× scaled V(ISP−ISN); outputs 1V at 100mV sense voltage - enables isolated current measurement and telemetry. |
| IVINMON (8) | Input current monitor output | 20× scaled V(IVINP−IVINN); outputs 1V at 50mV sense voltage - supports input power limiting and system-level energy monitoring. |
| EN/UVLO (9) | Enable & undervoltage lockout | 1.2V 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 trip threshold; 90µA/20µA input bias; common-mode range 3V–60V - supports high-side or low-side sensing. |
| VIN (12) | Main power input | Accepts 4.7–60V supply; bypass to PGND with ≥4.7µF ceramic capacitor; powers internal LDO and gate drivers. |
| INTVCC (13) | Internal 5V regulator output | 4.8–5.2V regulated supply for logic and gate drivers; requires ≥4.7µF ceramic bypass to PGND; 67mA current limit. |
| TG1/BG1 (14/18), TG2/BG2 (24/19) | N-channel MOSFET gate drivers | TG drivers: 2.6Ω pull-up / 1.7Ω pull-down (BST-referenced); BG drivers: 3Ω/1.2Ω (ground-referenced); support 100W+ operation. |
| SW1/SW2 (16/21) | Switch node terminals | SW1 connects to VIN-side inductor node; SW2 connects to VOUT-side inductor node; each swings from −0.3V to VIN/VOUT + 0.3V. |
| PGND (17,20) | Power ground | Low-impedance return path for bottom MOSFET sources and high-current paths; must be connected close to MOSFET source pads. |
| ISP/ISN (25/26) | LED current sense inputs | Differential pair with 100mV default trip threshold; ±6% accuracy over 0–52V LED range; 110µA/20µA input bias. |
| SNSP/SNSN (27/28) | Current comparator inputs | Direct inputs to internal current comparator; VC-controlled offset sets trip point; supports buck-boost region current sensing. |
| FB (37) | Output voltage feedback | Regulates to 1.176–1.220V; triggers OPENLED if >1.15V with zero LED current; triggers SHORTLED if <400mV - enables dual-fault protection. |
| VC (36) | Error amplifier output & current threshold control | 0.7–1.9V control voltage setting LED current limit; clamped by SS during soft-start; sum of three feedback loop contributions. |
| RT (35) | Oscillator frequency set | Resistor-to-GND sets switching frequency: 147kΩ → 200kHz, 59.0kΩ → 400kHz, 29.1kΩ → 700kHz - enables EMI spread-spectrum tuning. |
| SYNC/CLKOUT (34/33) | External sync & clock output | SYNC accepts 200–700kHz external clock; CLKOUT provides in-phase oscillator output for paralleling multiple controllers. |
| OVLO (38) | Overvoltage lockout | Shuts down converter if voltage exceeds 2.85–3.15V; pulls SS low to latch off - protects downstream loads from overvoltage events. |
| SGND (30, 39) | Signal ground | Reference for all small-signal pins (CTRL, FB, ISMON, etc.); must connect to PGND at single-point star ground to avoid noise coupling. |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor architecture | Enables continuous conduction mode operation with VIN above, below, or equal to VOUT - eliminates need for separate buck/boost converters in variable-input systems. |
| True Color PWM™ dimming | Maintains consistent LED chromaticity across 0.01%–100% duty cycle - critical for automotive adaptive driving beam (ADB) and high-CRI architectural lighting. |
| Integrated input & output current monitoring | ISMON and IVINMON provide isolated, scaled analog outputs (10× and 20×) - simplifies system-level power telemetry and closed-loop input current limiting. |
| Open/short LED fault protection | Dual independent comparators assert OPENLED and SHORTLED pins with defined thresholds - enables automatic load disconnect and diagnostic reporting without external circuitry. |
| –55°C to 150°C operating junction range | Qualified for extreme environments including engine compartments, industrial furnaces, and avionics bays - exceeds AEC-Q100 Grade 1 requirements. |
| No top MOSFET refresh in buck/boost | Eliminates unnecessary switching losses and gate drive complexity in pure buck or boost modes - improves efficiency by 1–2% versus conventional 4-switch controllers. |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
|
Use Scenario: Adaptive front-lighting system (AFS) requiring dynamic beam shaping across 9–16V battery input with LED string voltages from 12V (low-beam) to 48V (high-beam). IC Role / Device Role / Timing Role: Primary LED current controller managing four independent channels via multiplexed PWMOUT signals and synchronized CLKOUT. Use Value: Seamless buck-boost transition prevents beam flicker during voltage dips; ±6% current accuracy ensures consistent photometric output across temperature. |
Use Scenario: 100W+ high-bay fixture powered from 24–48V DC industrial bus, driving 36V LED strings with real-time input power monitoring. IC Role / Device Role / Timing Role: Constant-current regulator with IVINMON-based input power limiting to prevent overloading shared DC distribution lines. Use Value: Integrated IVINMON output enables direct connection to PLC analog inputs for centralized energy management; 98.5% peak efficiency reduces thermal load in enclosed fixtures. |
| Battery-Powered Emergency Lighting | UV-C Disinfection Systems |
|
Use Scenario: Portable emergency light using 12V sealed lead-acid battery with LED string voltage varying from 30V (fully charged) to 18V (discharged). IC Role / Device Role / Timing Role: Single-chip buck-boost controller eliminating need for separate DC-DC stages and enabling compact, lightweight design. Use Value: Wide 4.7–60V input range accommodates full battery discharge curve; SS pin latching provides fail-safe shutdown during LED open-circuit faults. |
Use Scenario: Pulsed UV-C LED array (365nm) requiring precise current control and thermal derating based on junction temperature feedback. IC Role / Device Role / Timing Role: LED current controller interfaced with external thermistor via CTRL pin to implement temperature-compensated dimming. Use Value: CTRL pin's linear 200mV–1.1V range allows direct mapping of thermistor voltage to LED current reduction - prevents UV-C LED degradation at elevated temperatures. |
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 boost diode driver. | Designed for new designs requiring higher power density and advanced diagnostics; not drop-in compatible due to different pinout and CTRL behavior. | Select LT8391EFE#TRPBF for new designs where layout revision is acceptable and higher performance justifies redesign effort. |
| LTC3789EGN#TRPBF | 4-switch buck-boost controller with 40V max input, no integrated LED-specific features (no OPENLED/SHORTLED, no ISMON), and narrower temp range (–40°C to 125°C). | General-purpose DC-DC conversion only; lacks LED protection, dimming interfaces, and current monitoring outputs required for lighting. | Consider LTC3789EGN#TRPBF only for non-LED applications such as battery-powered industrial sensors where LED-specific functions are unnecessary. |
Compared with LT8391EFE#TRPBF, the LT3791MPFE#TRPBF offers extended temperature qualification (–55°C to 150°C vs –40°C to 125°C) and mature design-in support, while LTC3789EGN#TRPBF lacks LED-specific protection and monitoring - making LT3791MPFE#TRPBF the sole choice for ruggedized LED lighting in harsh environments.
Availability
LT3791MPFE#TRPBF is available at Aetrix Electronics and suitable for automotive headlamp systems, industrial high-bay lighting, battery-powered emergency lighting, and UV-C disinfection equipment requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3791MPFE#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. (ADI) 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-reliability LED driver applications demanding seamless buck-boost operation, wide input/output voltage flexibility, and robust fault protection in extreme thermal environments.
FAQ
What is the maximum LED string voltage supported by the LT3791MPFE#TRPBF?
The LT3791MPFE#TRPBF supports LED string voltages up to 52V, as specified in the "Wide VOUT Range: 0V to 60V (52V LED)" feature. This 52V limit reflects the maximum forward voltage across the LED load under regulation, while the device's 60V absolute maximum output capability provides margin for transient conditions and sensing overhead. Operation beyond 52V risks violating the ±6% LED current accuracy specification.
Does the LT3791MPFE#TRPBF require external Schottky diodes for synchronous rectification?
No, the LT3791MPFE#TRPBF does not require external Schottky diodes across the synchronous switches. Its gate drivers and control logic are designed for fully synchronous operation. However, adding Schottky diodes across M2 and M4 can improve peak efficiency by 1–2% at 500kHz by reducing dead-time conduction loss - this is an optional enhancement, not a requirement.
How is the LT3791MPFE#TRPBF protected against overvoltage conditions on the output?
The LT3791MPFE#TRPBF uses the OVLO pin to detect overvoltage: when voltage on OVLO exceeds 2.85–3.15V, the controller pulls the SS pin low, halts switching, and enters latch-off state. This action disconnects the output from the input and prevents damage to downstream LEDs or optics. The OVLO threshold is internally trimmed and temperature-compensated for reliable protection across the full –55°C to 150°C junction range.
Can the LT3791MPFE#TRPBF operate with input voltage below 4.7V?
No, the LT3791MPFE#TRPBF has a minimum specified input voltage of 4.7V per Absolute Maximum Ratings and Electrical Characteristics tables. Below this, internal regulation (INTVCC) cannot be sustained, gate drivers lose drive strength, and current sense amplifier accuracy degrades. Attempting operation below 4.7V may result in erratic behavior, failure to start, or undefined fault responses - it is outside the validated operating envelope.
What is the function of the exposed pad (Pin 39) on the LT3791MPFE#TRPBF package?
The exposed pad (Pin 39) on the LT3791MPFE#TRPBF is designated SGND and must be soldered directly to the PCB ground plane. It serves dual purposes: (1) providing low-thermal-resistance heat dissipation (θJA = 28°C/W), and (2) establishing the reference for all small-signal circuitry. Leaving it unconnected or floating violates the Absolute Maximum Ratings and will cause functional failure, thermal runaway, or inaccurate current regulation.
LT3791MPFE#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:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT3791MPFE#TRPBF FAQ
1.How can I place an order for LT3791MPFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3791MPFE#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 LT3791MPFE#TRPBF reliable?
The price and inventory of LT3791MPFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3791MPFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3791MPFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3791MPFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3791MPFE#TRPBF?
LT3791MPFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3791MPFE#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 LT3791MPFE#TRPBF?
For technical support, including LT3791MPFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3791MPFE#TRPBF requirements.
6.How does Aetrix verify that LT3791MPFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3791MPFE#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 LT3791MPFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3791MPFE#TRPBF?
All LT3791MPFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3791MPFE#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 LT3791MPFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3791MPFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3791MPFE#TRPBF Tags
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