My Inquiry
My Account
Analog Devices Inc. LT3791MPFE#PBF
- Part No.:
- LT3791MPFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3791MPFE#PBF.pdf
- Description:
- IC LED DRIVER CTRLR PWM 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,919
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT3791MPFE#PBF from Analog Devices is a 60V synchronous 4-switch buck-boost LED driver controller designed for automotive and industrial lighting systems. It regulates LED current up to 52V with input voltages from 4.7V to 60V, supports true color PWM and analog dimming, achieves ±6% LED current accuracy, and operates at adjustable frequencies from 200kHz to 700kHz.
For engineers reviewing the LT3791MPFE#PBF datasheet, LT3791MPFE#PBF pinout, LT3791MPFE#PBF application, or LT3791MPFE#PBF equivalent, key selection criteria include its wide VIN/VOUT range (4.7–60V), seamless buck/boost/buck-boost transitions, open/shorted LED fault protection, and –55°C to 150°C operating junction temperature rating.
Technical Context
The LT3791MPFE#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.
It integrates dual high-side gate drivers (TG1/TG2) with bootstrap supplies (BST1/BST2), dual low-side drivers (BG1/BG2), precision current sense comparators (SNSP/SNSN), and dedicated monitor outputs (ISMON, IVINMON) scaling sensed voltages by ×10 and ×20 respectively for system-level diagnostics.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4.7V to 60V - supports 12V/24V/48V automotive and industrial rails without external pre-regulation |
| VOUT Capability | 0V to 60V (52V LED string) - enables direct drive of multi-LED strings without intermediate converters |
| Switching Frequency | 200kHz to 700kHz - adjustable via RT resistor; allows EMI optimization and inductor size reduction |
| LED Current Accuracy | ±6% (0V ≤ VLED < 52V) - ensures consistent luminance across temperature and line/load variations |
| Junction Temp Range | –55°C to 150°C - qualified for under-hood automotive and harsh-environment industrial use |
| Efficiency | Up to 98.5% - achieved in 100W (33.3V/3A) buck-boost configuration, minimizing thermal design burden |
| Fault Protection | Open/shorted LED detection with OPENLED/SHORTLED pins - provides fail-safe shutdown and system-level status signaling |
Pinout & Package
LT3791MPFE#PBF is housed in a 38-lead plastic TSSOP package with exposed pad (Pin 39 = SGND), optimized for thermal dissipation in high-power LED driver applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CTRL (1) | Analog dimming threshold adjust | Sets LED current sense threshold from 6.5mV to 100mV; linear control below 1.1V, clamped above 1.3V |
| SS (2) | Soft-start/fault timer | Controls startup inrush current; latches off during open/short LED faults when pulled to VREF via 500kΩ |
| PWM (3) | Digital dimming enable | Directly disables switching and disconnects VC; drives PWMOUT for external LED disconnect MOSFET |
| 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 source | Stable 2V output driving CTRL divider; supplies up to 200µA for external circuitry |
| ISMON (7) | LED current monitor | 10× scaled V(ISP-ISN); outputs 1V at 100mV sense voltage for diagnostic or closed-loop feedback |
| IVINMON (8) | Input current monitor | 20× scaled V(IVINP-IVINN); outputs 1V at 50mV sense voltage for 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 sensing input current; 50mV threshold triggers input current regulation |
| VIN (12) | Main power input | Accepts 4.7–60V; bypassed to PGND with ≥4.7µF ceramic capacitor for stability |
| INTVCC (13) | Internal 5V regulator output | Supplies gate drivers and logic; requires ≥4.7µF ceramic bypass to PGND |
| TG1/BST1/SW1 (14–16) | Buck-side high-side switch interface | TG1 drives M1 gate; BST1 supplies floating gate drive; SW1 connects to inductor and M1/M2 nodes |
| PGND (17,20) | Power ground return | Low-impedance path for bottom MOSFET sources; must be connected close to MOSFET source pads |
| BG1/BG2 (18–19) | Low-side gate drivers | Drive M2 and M3 gates between SGND and INTVCC; 1.2Ω pull-down resistance ensures fast turn-off |
| SW2/BST2/TG2 (21–22,24) | Boost-side high-side switch interface | TG2 drives M4 gate; BST2 supplies floating gate drive; SW2 connects to output and M3/M4 nodes |
| ISP/ISN (25–26) | LED current sense inputs | Differential pair sensing LED current; 100mV default threshold scalable via CTRL pin |
| SNSP/SNSN (27–28) | Current comparator inputs | Compare VC-derived threshold against sensed current; determine switching timing in all modes |
| TEST1 (29)/SGND (30) | Signal ground reference | SGND (Pin 30 + Exposed Pad 39) is signal ground; must tie to PGND at single point |
| PWMOUT (31) | Buffered PWM output | INTVCC-referenced logic-level output mirroring PWM pin; drives external N-MOSFET for LED disconnect |
| TEST2 (32) | Factory test pin | Must connect to INTVCC (Pin 13) for normal operation; not for user circuitry |
| CLKOUT (33) | Master clock output | Provides in-phase oscillator signal for synchronizing multiple LT3791 controllers in parallel designs |
| SYNC (34) | External clock input | Accepts 200–700kHz external clock; internal 90kΩ pull-down enables synchronization without external resistor |
| RT (35) | Frequency set resistor | Resistor to SGND sets oscillator frequency: 147kΩ = 200kHz, 59.0kΩ = 400kHz, 29.1kΩ = 700kHz |
| VC (36) | Error amplifier output | 0.7–1.9V control voltage setting current limit; clamped by SS during soft-start and faults |
| FB (37) | Output voltage feedback | Regulates to 1.2V; detects open LED (>1.15V) and shorted LED (<400mV) for fault signaling |
| OVLO (38) | Overvoltage lockout | Shuts down converter if >3.0V applied; prevents output overvoltage damage to LEDs or downstream circuitry |
Key Features
| Feature | Design Value |
|---|---|
| 4-switch single-inductor topology | Enables continuous VIN-to-VOUT conversion without mode gaps-no discontinuity at VIN = VOUT |
| True Color PWM™ dimming | Maintains precise LED color point across full dimming range by eliminating low-frequency current ripple |
| No top MOSFET refresh cycle | Eliminates unnecessary switching losses in buck/boost-only operation, improving efficiency by ~1–2% |
| VOUT disconnected from VIN during shutdown | Prevents backfeed into input supply when disabled-critical for battery-powered systems |
| Integrated current monitor outputs | ISMON and IVINMON provide real-time, scaled diagnostics without external op-amps or ADCs |
Applications
| Automotive Head Lamps | Industrial High-Bay Lighting |
|---|---|
Use Scenario: Adaptive front-lighting systems requiring dynamic beam shaping and high-lumen output across varying battery voltages (9–16V). IC Role / Device Role / Timing Role: Primary LED current controller managing 33.3V/3A (100W) LED arrays with seamless buck-boost transitions as engine cranking drops input voltage. Use Value: Maintains constant LED brightness and color fidelity during cold cranking (down to 4.7V VIN) and alternator overvoltage (up to 60V), eliminating need for auxiliary DC/DC stages. | Use Scenario: Factory floor lighting using long LED strings powered from 48V DC distribution buses. IC Role / Device Role / Timing Role: Constant-current driver regulating 52V LED strings while accepting variable input (36–60V) due to cable drop and load transients. Use Value: Delivers 98.5% peak efficiency at 100W, reducing thermal load in enclosed fixtures and enabling smaller heatsinks versus conventional buck-only solutions. |
| Emergency Vehicle Warning Lights | Outdoor Street Lighting |
Use Scenario: Flashing red/blue LED arrays in police/fire vehicles requiring rapid on/off cycling and robust fault handling. IC Role / Device Role / Timing Role: PWM-controlled LED driver with integrated OPENLED/SHORTLED fault flags feeding vehicle CAN bus diagnostics. Use Value: Detects open-circuit failures within 10ms and asserts OPENLED pin, enabling immediate driver replacement alerts before total lamp failure. | Use Scenario: Smart streetlights with adaptive dimming based on ambient light and occupancy, powered from solar-charged 24V batteries. IC Role / Device Role / Timing Role: Buck-boost controller maintaining 36V LED output despite battery voltage sagging from 28V to 20V at end-of-discharge. Use Value: Extends usable battery runtime by 18% compared to buck-only drivers, as it continues regulating down to 4.7V input without dropout. |
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 higher efficiency (99%), lower IQ (2.5mA vs 4mA), integrated boost diode driver, and improved thermal performance. | Targeted for new designs where footprint compatibility is acceptable and higher reliability under thermal stress is required. | Select LT8391EFE#PBF for new designs seeking best-in-class efficiency and reduced BOM count; LT3791MPFE#PBF remains valid for legacy qualification or extended temperature needs. |
| LTC3789EGN#PBF | 4-switch buck-boost controller with 36V max VIN/VOUT, no integrated LED-specific features (no ISMON, OPENLED/SHORTLED), and narrower temp range (–40°C to 125°C). | Suitable for general DC/DC conversion but lacks LED current monitoring, fault signaling, and dimming interfaces. | Choose LTC3789EGN#PBF only if LED-specific functions are unnecessary and input/output voltage stays ≤36V. |
Compared with LT8391EFE#PBF and LTC3789EGN#PBF, the LT3791MPFE#PBF uniquely combines military-grade temperature range (–55°C to 150°C), integrated LED fault signaling, and proven field reliability in automotive headlamp modules-making it irreplaceable where extreme environmental qualification is mandatory.
Availability
LT3791MPFE#PBF is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and emergency warning systems requiring stable component supply across extended temperature and long product lifecycles.
Supply support for LT3791MPFE#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.
The LT3791MPFE#PBF belongs to Linear's LED driver controller product line, engineered specifically for high-reliability, wide-input-range LED lighting in automotive and industrial environments where seamless buck-boost operation and fault resilience are critical.
FAQ
What is the maximum LED string voltage supported by the LT3791MPFE#PBF?
The LT3791MPFE#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 enables direct drive of long LED strings without intermediate voltage conversion, and the device maintains ±6% LED current accuracy across the full 0V to 52V range.
Does the LT3791MPFE#PBF require external Schottky diodes for proper operation?
No, the LT3791MPFE#PBF does not require external Schottky diodes for basic operation. The datasheet states that "Schottky diodes across the synchronous switch M4 and synchronous switch M2 are not required," though their addition improves peak efficiency by 1–2% at 500kHz. The controller's gate drive timing and dead-time control ensure safe commutation without them.
How does the LT3791MPFE#PBF handle input voltage dropout during cold cranking?
The LT3791MPFE#PBF handles cold cranking by maintaining regulation down to 4.7V input-well below typical automotive cranking dips (~6–7V). Its 4-switch architecture seamlessly transitions from buck to buck-boost mode as VIN approaches VOUT, preventing output collapse. The –55°C to 150°C junction temperature rating further ensures functionality during extreme cold starts.
Can the LT3791MPFE#PBF be synchronized to an external clock?
Yes, the LT3791MPFE#PBF supports external synchronization via its SYNC pin (Pin 34), which accepts clock signals from 200kHz to 700kHz. The pin has an internal 90kΩ pull-down resistor, so no external components are needed beyond the clock source. This enables precise phase alignment in multi-phase or parallel LED driver configurations to reduce input/output ripple.
What is the purpose of the TEST1 and TEST2 pins on the LT3791MPFE#PBF?
TEST1 (Pin 29) must be connected to SGND, and TEST2 (Pin 32) must be connected to INTVCC for the LT3791MPFE#PBF to operate correctly. These are factory test pins with no user functionality; leaving them unconnected or miswired will prevent normal operation. The exposed pad (Pin 39) is also SGND and must be soldered to the PCB ground plane for thermal and electrical integrity.
LT3791MPFE#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:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LT3791MPFE#PBF FAQ
1.How can I place an order for LT3791MPFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3791MPFE#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 LT3791MPFE#PBF reliable?
The price and inventory of LT3791MPFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3791MPFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3791MPFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3791MPFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3791MPFE#PBF?
LT3791MPFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3791MPFE#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 LT3791MPFE#PBF?
For technical support, including LT3791MPFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3791MPFE#PBF requirements.
6.How does Aetrix verify that LT3791MPFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3791MPFE#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 LT3791MPFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3791MPFE#PBF?
All LT3791MPFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3791MPFE#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 LT3791MPFE#PBF part is unused and in its original packaging.
Return procedure for LT3791MPFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT3791MPFE#PBF Tags
-
BCR402RE6327HTSA1
Infineon Technologies
-
BCR430UXTSA2
Infineon Technologies
-
BCR420UE6433HTMA1
Infineon Technologies
-
BCR420UE6327HTSA1
Infineon Technologies
-
BCR421UE6327HTSA1
Infineon Technologies
-
LYT1604D-TL
Power Integrations
-
HV9910CLG-G
Microchip Technology
-
CL2N8-G
Microchip Technology
-
BCR420UW6-7
Diodes Incorporated
-
BCR421UW6-7
Diodes Incorporated
-
BCR420UFD-7
Diodes Incorporated
-
BCR421UFD-7
Diodes Incorporated
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
