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Analog Devices Inc. LT3641EUFD#PBF
- Part No.:
- LT3641EUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT3641EUFD#PBF.pdf
- Description:
- IC REG BCK ADJ 1.3A/1.DL 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,922
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Product details
Overview
LT3641EUFD#PBF from Analog Devices (formerly Linear Technology) is a dual-channel monolithic buck switching regulator IC with integrated power-on reset and window-mode watchdog timer. It delivers 5V/0.8A from 7–42V input (HV channel) and 3.3V/0.5A from 2.5–5.5V input (LV channel), operating synchronously at 2MHz in a thermally enhanced 28-pin 4mm × 5mm QFN package. It serves as a compact, fault-protected DC/DC power management solution for automotive ECU and industrial control systems.
For engineers reviewing the LT3641EUFD#PBF datasheet, LT3641EUFD#PBF pinout, LT3641EUFD#PBF application, or LT3641EUFD#PBF equivalent, key selection considerations include its dual-input voltage ranges (4–42V HV + 2.5–5.5V LV), programmable reset/watchdog timing via external capacitors, Burst Mode® operation for light-load efficiency, and thermal shutdown with exposed-pad thermal management.
Technical Context
The LT3641EUFD#PBF integrates two independent current-mode buck regulators sharing a single adjustable oscillator (350kHz–2.5MHz). The high-voltage channel uses a nonsynchronous NPN switch with internal 2.4A top switch and 55V transient protection; the low-voltage channel employs synchronous NMOS/PMOS switches with 1.1A combined current limit and no external Schottky diode required.
Both channels feature cycle-by-cycle current limiting, programmable soft-start (SS1/SS2), and output regulation referenced to precise internal references (1.265V for FB1, 600mV for FB2). Power-on reset (RST1/RST2) and window-mode watchdog (WDO/WDI/CWDT/CPOR) are independently configurable via external capacitors and operate with defined timing boundaries (e.g., tWDL = 1.68–2.2ms, tWDU = 27–35ms at CWDT = 820pF).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| HV Input Range | 4V to 42V continuous, with 55V nonrepetitive transient protection - enables robust operation in automotive battery-supplied systems. |
| LV Input Range | 2.5V to 5.5V - supports direct connection to intermediate rails (e.g., 3.3V or 5V outputs) or standalone low-voltage sources. |
| Switching Frequency | Adjustable 350kHz to 2.5MHz via RT resistor - allows optimization of inductor size vs. efficiency (e.g., 2MHz used in typical 5V/0.8A + 3.3V/0.5A design). |
| Quiescent Current | 290μA typical - maintains high light-load efficiency in always-on subsystems without compromising startup speed. |
| Reset Timeout (tRST) | 8–11ms with CPOR = 220pF - provides deterministic power sequencing for microcontrollers requiring stable VDD before release. |
| Watchdog Window | Lower boundary 1.68–2.2ms, upper boundary 27–35ms (CWDT = 820pF) - detects both stuck and runaway μP behavior in safety-critical applications. |
| Thermal Package | 28-pin 4mm × 5mm QFN with exposed GND pad (θJC = 3.4°C/W) - enables >2W dissipation in compact layouts without heatsinks. |
Pinout & Package
LT3641EUFD#PBF is housed in a 28-lead plastic QFN package (4mm × 5mm) with exposed thermal pad (Pin 29, GND). The package supports low thermal resistance (θJA = 43°C/W, θJC = 3.4°C/W) and requires soldering of the exposed pad to PCB ground for reliable thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 (Pin 6) | High-voltage feedback input | Regulates to 1.265V reference; sets VOUT1 via resistor divider - determines accuracy and stability of primary 5V rail. |
| FB2 (Pin 1) | Low-voltage feedback input | Regulates to 600mV reference; sets VOUT2 (e.g., 3.3V) - enables precise secondary rail control with minimal external components. |
| RT (Pin 7) | Oscillator frequency programming | Resistor-to-ground sets switching frequency (350kHz–2.5MHz); 32.4kΩ yields 2MHz - balances efficiency and component size. |
| CPOR (Pin 12) | Power-on reset & WDO timer capacitor | Capacitor-to-ground programs RST1/RST2 timeout and WDO assertion period - enables system-level sequencing and watchdog initialization. |
| CWDT (Pin 11) | Watchdog timing capacitor | Capacitor-to-ground sets watchdog window boundaries (tWDL/tWDU) - defines valid pulse interval for μP watchdog signals. |
| EN/UVLO (Pin 3) | Global enable & VIN undervoltage lockout | 1.26V threshold with 2μA hysteresis - allows programmable VIN start-up voltage (e.g., 7V) using external resistor divider. |
| EN2 (Pin 27) | LV channel enable | Threshold at 100mV below FB2 target (e.g., 500mV for 3.3V out); 50mV hysteresis - provides independent control and UVLO for secondary rail. |
| PGOOD2 (Pin 2) | LV output power-good indicator | Open-drain output asserted when FB2 ≥ 550mV (±40mV hysteresis) - signals stable 3.3V rail for downstream logic enable. |
| WDO (Pin 10) | Watchdog timeout output | Open-drain reset signal asserted when WDI pulses violate window - directly resets μP or triggers system fault handler. |
| GND (Pins 15,16,23,26,29) | Power and signal ground | Multiple dedicated GND pins + exposed thermal pad - ensures low-impedance return paths and thermal conduction to PCB plane. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent buck regulation | Simultaneous 5V/0.8A (HV) and 3.3V/0.5A (LV) outputs from separate inputs - eliminates need for cascaded converters in multi-rail systems. |
| Burst Mode® operation | Maintains <15mVpp output ripple and >85% efficiency at 1mA load - extends battery life in standby modes without compromising noise-sensitive analog circuits. |
| Programmable window-mode watchdog | Configurable lower/upper timing boundaries detect both missed and excessive WDI pulses - increases system reliability beyond standard timeout watchdogs. |
| Input transient protection | Withstands 55V/1s transients on VIN - meets ISO 7637-2 Pulse 1/2/5a requirements for automotive 12V systems. |
| Thermally enhanced QFN | 4mm × 5mm footprint with exposed GND pad (θJC = 3.4°C/W) - achieves full rated output power in space-constrained industrial modules. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering MCU, CAN transceiver, and sensor interface circuitry in under-hood engine control units exposed to wide temperature and load dump conditions. IC Role / Device Role / Timing Role: Primary dual-rail DC/DC converter providing regulated 5V (MCU core) and 3.3V (peripheral logic), with watchdog supervision of MCU execution integrity. Use Value: 55V transient tolerance prevents shutdown during load dump; window watchdog detects firmware hangs that could cause unsafe actuator behavior. | Use Scenario: Generating isolated 5V and 3.3V rails for digital I/O conditioning, ADC reference, and FPGA configuration in modular programmable logic controllers. IC Role / Device Role / Timing Role: Compact, self-contained power manager delivering sequenced, monitored outputs - replaces discrete LDO + supervisor + watchdog IC combinations. Use Value: Integrated POR and programmable reset timing ensure deterministic boot sequence; Burst Mode® reduces idle power in distributed I/O nodes. |
| Medical Diagnostic Imaging Subsystem | Ruggedized Data Acquisition Node |
Use Scenario: Supplying precision analog front-end (AFE) and digital processing blocks in portable ultrasound or X-ray detector modules. IC Role / Device Role / Timing Role: Dual-output regulator with ultra-low quiescent current and tight output voltage accuracy (±1.2% FB1, ±2.5% FB2) - maintains signal chain SNR and timing stability. Use Value: 290μA IQ minimizes self-heating in sealed enclosures; 40mV PGOOD2 hysteresis prevents false power-good toggling near regulation threshold. | Use Scenario: Powering wireless sensor nodes deployed in harsh environments (e.g., oil/gas field monitoring) with extended battery life and fault resilience. IC Role / Device Role / Timing Role: Fault-tolerant power source combining input overvoltage protection, short-circuit robustness, and watchdog-enforced software health checks. Use Value: Cycle-by-cycle current limiting survives sustained shorts; programmable watchdog window adapts to variable sensor sampling intervals. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3642EFE#PBF | Single-channel 40V buck with integrated power path management and higher 2.5A HV switch; lacks LV channel and watchdog. | Suitable only where dual-rail generation is not required; no built-in μP supervision capability. | Select when needing higher HV current and battery backup support, but accept loss of integrated watchdog and secondary rail. |
| TPS65270QPWPRQ1 | Automotive-grade dual-buck (3A + 2A) with fixed 5V/3.3V outputs, no programmable watchdog, and different pinout. | Fixed-output version optimized for infotainment head units; no external timing capacitor flexibility for reset/watchdog. | Choose for AEC-Q100-compliant designs requiring higher current and qualification, but sacrifice programmability and thermal QFN advantage. |
Compared with LTC3642EFE#PBF and TPS65270QPWPRQ1, the LT3641EUFD#PBF uniquely combines dual independent regulation, programmable window watchdog, 55V transient tolerance, and thermally optimized QFN in a single 28-pin package - making it optimal for space-constrained, safety-aware embedded systems requiring flexible sequencing and supervision.
Availability
LT3641EUFD#PBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial PLC modules, and medical diagnostic subsystems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LT3641EUFD#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 leader in high-performance analog, mixed-signal, and digital signal processing technologies, formed through the acquisition of Linear Technology in 2017.
The LT3641EUFD#PBF belongs to ADI's Power by Linear™ family of highly integrated DC/DC regulators, designed specifically for demanding automotive, industrial, and medical applications requiring robustness, precision, and functional safety features.
FAQ
What is the maximum input voltage rating for LT3641EUFD#PBF during transient events?
The LT3641EUFD#PBF supports up to 55V on the VIN pin for nonrepetitive 1-second transients, while continuous operation is rated for 4V to 42V. This 55V transient rating meets ISO 7637-2 Pulse 5a requirements for automotive 12V systems and enables robust operation in industrial environments with inductive load switching. The LT3641EUFD#PBF incorporates internal clamping and protection circuitry to sustain this rating without external components.
How does the window-mode watchdog in LT3641EUFD#PBF differ from a standard timeout watchdog?
The LT3641EUFD#PBF implements a true window-mode watchdog that monitors both minimum and maximum allowable intervals between WDI pulses - detecting both stuck (no pulses) and runaway (excessively frequent pulses) microprocessor behavior. Unlike simple timeout watchdogs, this dual-boundary detection prevents false resets due to jitter and catches firmware loops that generate rapid spurious pulses. The LT3641EUFD#PBF allows independent adjustment of lower (tWDL) and upper (tWDU) boundaries via CWDT capacitor value.
Can LT3641EUFD#PBF generate both 5V and 3.3V outputs simultaneously from separate input sources?
Yes, the LT3641EUFD#PBF supports independent input supplies: the HV channel accepts 4–42V on VIN for 5V output, while the LV channel accepts 2.5–5.5V on VIN2 for 3.3V output. This allows direct connection of VIN2 to an auxiliary 3.3V or 5V rail, or to the HV channel's VOUT1, enabling flexible two-stage or split-supply architectures. Each channel has dedicated enable (EN/UVLO and EN2), feedback (FB1/FB2), and soft-start (SS1/SS2) controls for independent sequencing.
What thermal performance can be expected from the LT3641EUFD#PBF QFN package?
The LT3641EUFD#PBF uses a 28-pin 4mm × 5mm QFN with exposed thermal pad (Pin 29, GND), achieving θJC = 3.4°C/W and θJA = 43°C/W with standard 2-layer PCB layout. When the exposed pad is soldered to a 1-in² copper area, the device sustains full 0.8A/0.5A output currents at 125°C ambient without derating. This thermal performance exceeds equivalent TSSOP packages (θJA = 30°C/W) and enables compact, fanless designs in enclosed industrial enclosures.
Is LT3641EUFD#PBF compatible with external clock synchronization?
Yes, the LT3641EUFD#PBF supports external clock synchronization via the SYNC pin (Pin 4), accepting 350kHz–2.5MHz TTL/CMOS clock signals. The internal oscillator frequency must be set at least 20% lower than the minimum SYNC frequency using the RT resistor. Synchronization begins only after FB1 reaches 1.165V, preventing erratic startup. This feature enables EMI reduction through spread-spectrum clock alignment and deterministic timing across multiple converters in dense PCB layouts.
LT3641EUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 2
- Voltage - Input (Min):
- 2.5V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 0.6V, 1.265V
- Voltage - Output (Max):
- 39.48V
- Current - Output:
- 1.3A, 1.1A
- Frequency - Switching:
- 500kHz ~ 2MHz
- Synchronous Rectifier:
- Both
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LT3641EUFD#PBF FAQ
1.How can I place an order for LT3641EUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3641EUFD#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 LT3641EUFD#PBF reliable?
The price and inventory of LT3641EUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3641EUFD#PBF is usually 5 days.
3.What payment methods are accepted for LT3641EUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3641EUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3641EUFD#PBF?
LT3641EUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3641EUFD#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 LT3641EUFD#PBF?
For technical support, including LT3641EUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3641EUFD#PBF requirements.
6.How does Aetrix verify that LT3641EUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3641EUFD#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 LT3641EUFD#PBF meets industry standards.
7.What is the process for return or replacement of LT3641EUFD#PBF?
All LT3641EUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3641EUFD#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 LT3641EUFD#PBF part is unused and in its original packaging.
Return procedure for LT3641EUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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