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Analog Devices Inc. LT3641IUFD#TRPBF
- Part No.:
- LT3641IUFD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT3641IUFD#TRPBF.pdf
- Description:
- IC REG BCK ADJ 1.3A/1.DL 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,377
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Product details
Overview
LT3641IUFD#TRPBF 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 automotive ECU power rails.
For engineers reviewing the LT3641IUFD#TRPBF datasheet, LT3641IUFD#TRPBF pinout, LT3641IUFD#TRPBF application, or LT3641IUFD#TRPBF equivalent, key selection criteria include its dual-input voltage ranges (4–42V HV + 2.5–5.5V LV), programmable 350kHz–2.5MHz switching frequency via RT resistor, adjustable POR/watchdog timing via external capacitors, and thermally enhanced 28-pin 4mm × 5mm QFN package with exposed GND pad.
Technical Context
The LT3641IUFD#TRPBF integrates two independent current-mode buck regulators sharing a single adjustable oscillator. 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 PMOS/NMOS switches with 1.1A combined current limit and no external Schottky diode required.
Both channels feature cycle-by-cycle current limiting, programmable soft-start via SS1/SS2 pins, and independent enable/UVLO logic (EN/UVLO at 1.26V threshold, EN2 referenced to FB2). The integrated window-mode watchdog monitors microprocessor pulse timing-asserting WDO if WDI edges fall outside tWDL (1.68–2.2ms) or tWDU (27–35ms) boundaries set by CWDT capacitor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| HV Input Range | 4V to 42V continuous, with 55V nonrepetitive transient protection - enables direct connection to automotive battery rails including cold-crank and load-dump conditions. |
| LV Input Range | 2.5V to 5.5V - supports post-regulation from HV output or independent low-voltage sources like USB or LDOs. |
| Switching Frequency | 350kHz to 2.5MHz, set by RT resistor or external SYNC clock - allows optimization of inductor size vs. efficiency; 2MHz operation enables <1μH inductors. |
| FB1 Reference | 1.265V ±15mV over temperature - sets HV output voltage via resistor divider; enables precise 5V/3.3V/other outputs with 1% resistors. |
| FB2 Reference | 600mV ±15mV over temperature - sets LV output voltage; lower reference improves accuracy for sub-2V core supplies. |
| Quiescent Current | 290μA typical - maintains high light-load efficiency in always-on subsystems without sacrificing startup speed. |
| Thermal Package | 28-pin 4mm × 5mm QFN with exposed GND pad (θJC = 3.4°C/W) - delivers low thermal resistance for 1.3A HV + 1.1A LV simultaneous operation at full load. |
Pinout & Package
LT3641IUFD#TRPBF is housed in a thermally enhanced 28-pin (4mm × 5mm) plastic QFN package with exposed GND pad (Pin 29), requiring soldering to PCB ground for optimal thermal performance (θJA = 43°C/W, θJC = 3.4°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 (Pin 6) | High-voltage feedback input | Regulated to 1.265V; connects to resistor divider tap to set VOUT1 (e.g., 5V or 3.3V). |
| FB2 (Pin 1) | Low-voltage feedback input | Regulated to 600mV; connects to resistor divider tap to set VOUT2 (e.g., 3.3V or 1.8V). |
| EN/UVLO (Pin 3) | Global enable / VIN undervoltage lockout | 1.26V threshold enables programmable UVLO; pulls below 0.3V for shutdown (<1μA IQ). |
| EN2 (Pin 27) | LV channel enable | Threshold at 1.18V (100mV below FB2 target); includes 80mV hysteresis for noise immunity. |
| CPOR (Pin 12) | Power-on reset & WDO timeout capacitor | Connects to capacitor to set RST1/RST2 assertion time (8–11ms) and WDO hold time. |
| CWDT (Pin 11) | Watchdog timing capacitor | Connects to capacitor to set watchdog window boundaries (tWDL/tWDU) and start delay (tDLY). |
| WDI (Pin 14) | Watchdog input | Accepts µP pulses; falling edges trigger window monitoring; 0.85V threshold with 300ns min pulse width. |
| WDE (Pin 13) | Watchdog enable | Active-high; must be pulled >0.7V to activate watchdog function and WDO output. |
| PGOOD2 (Pin 2) | LV output power-good flag | Open-drain output asserted when FB2 ≥ 590mV (40mV hysteresis); indicates stable VOUT2 regulation. |
| SW1 (Pin 19) | HV switch node | Connects to HV inductor and catch diode cathode; handles up to 2.4A peak current. |
| SW2 (Pin 25) | LV switch node | Connects to LV inductor; synchronous NMOS/PMOS switching eliminates external diode. |
| BST (Pin 21) | Bootstrap supply for HV switch | Drives HV NPN gate via external diode/capacitor; requires ≥2.3V BST–SW for full saturation. |
| DA (Pin 18) | Catch diode anode sense | Monitors diode conduction for valley current limiting and fault protection during short-circuit events. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-input architecture | Independent HV (4–42V) and LV (2.5–5.5V) inputs eliminate need for pre-regulator stages in multi-rail systems. |
| Window-mode watchdog | Rejects both too-frequent and too-infrequent µP pulses - prevents false resets due to software hangs or clock glitches. |
| Programmable soft-start | Independent SS1/SS2 pins allow controlled ramp-up of each output, preventing inrush current and enabling sequencing. |
| Burst Mode® operation | Maintains <15mVpp output ripple at light loads while sustaining >85% efficiency - critical for standby power compliance. |
| Thermal robustness | Integrated thermal shutdown plus exposed pad package supports continuous 1.3A HV + 1.1A LV operation at 85°C ambient. |
Applications
| Automotive ECU Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering MCU, CAN transceiver, and sensor interface in engine control unit under 12V/24V battery with load dump transients. IC Role / Device Role / Timing Role: Dual-buck regulator providing isolated 5V (MCU core) and 3.3V (peripherals) with synchronized switching to minimize EMI. Use Value: 55V transient tolerance on VIN and window watchdog ensure reliable operation during cranking and alternator spikes without external TVS or supervision IC. | Use Scenario: Generating 3.3V and 5V rails for digital I/O isolation, ADC reference, and fieldbus PHY in programmable logic controller backplane. IC Role / Device Role / Timing Role: Primary DC-DC converter with POR and watchdog used for system-level fault detection and safe power-up sequencing. Use Value: Independent EN2 and RST2 enable staggered power-up of analog and digital sections; CPOR/CWDT capacitors simplify BOM vs discrete timers. |
| Medical Diagnostic Imaging Subsystem | Test & Measurement Equipment |
Use Scenario: Supplying low-noise 3.3V for FPGA configuration and 1.8V for ADC front-end in portable ultrasound probe electronics. IC Role / Device Role / Timing Role: High-efficiency dual-output regulator with Burst Mode® maintaining <290μA quiescent current during idle scan states. Use Value: 600mV FB2 reference enables accurate 1.8V output with minimal resistor tolerance error; SS2 pin allows tracking to main 3.3V rail. | Use Scenario: Providing stable 5V/0.8A and 3.3V/0.5A to microcontroller, display driver, and precision DAC in handheld calibrator. IC Role / Device Role / Timing Role: Single-chip solution replacing discrete buck + supervisor + watchdog, reducing board area by >40%. Use Value: 2MHz switching frequency permits use of 1.0μH/2.2μH shielded inductors, minimizing magnetic coupling into sensitive analog signal paths. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-buck regulator with supervision applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EFE#TRPBF | Single-channel 4–42V buck with integrated watchdog and POR; no LV channel or synchronous rectification. | Suitable only where only one regulated rail is needed; lacks dual-output capability and LV efficiency advantage. | Select when space or cost constraints prohibit dual-channel design and system can derive LV rail externally. |
| TPS65217CZQZR | Quad-buck PMIC with integrated LDOs, battery charger, and fuel gauge; 2.7–5.5V input only; no HV channel or 55V transient rating. | Targeted at portable battery-powered systems, not automotive/industrial wide-input applications. | Choose for battery-backed embedded devices requiring multiple rails and power management, not wide-VIN industrial use. |
Compared with LTC3631EFE#TRPBF and TPS65217CZQZR, the LT3641IUFD#TRPBF uniquely combines wide-input HV buck, efficient LV synchronous buck, and window watchdog in one QFN - eliminating external supervision ICs while supporting harsh automotive transients and precise dual-rail sequencing.
Availability
LT3641IUFD#TRPBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial PLC modules, and medical diagnostic imaging subsystems requiring stable component supply across extended temperature and transient-voltage conditions.
Supply support for LT3641IUFD#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 leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3641 product line was designed by Linear Technology specifically for demanding dual-rail power management in automotive and industrial environments where input transients, thermal density, and system-level reliability (POR/watchdog) are critical.
FAQ
What is the maximum input voltage rating for LT3641IUFD#TRPBF during transient conditions?
The LT3641IUFD#TRPBF supports nonrepetitive 55V transients on the VIN pin for up to 1 second, per Absolute Maximum Ratings. Continuous operation is limited to 42V. This 55V rating enables robust operation during automotive load-dump events without external clamping components. The device remains functional and protected throughout the transient, and LT3641IUFD#TRPBF resumes normal regulation once VIN returns within spec.
How does the window-mode watchdog in LT3641IUFD#TRPBF differ from standard timeout watchdogs?
The LT3641IUFD#TRPBF implements a true window-mode watchdog that detects both too-close (fast) and too-far (slow) WDI pulse edges using independently set lower (tWDL = 1.68–2.2ms) and upper (tWDU = 27–35ms) boundaries. Unlike simple timeout watchdogs, this prevents false resets caused by µP clock stretching or jitter, and catches stuck-at-low or stuck-at-high WDI faults. The LT3641IUFD#TRPBF asserts WDO only when pulses violate either boundary, enhancing system reliability in safety-critical applications.
Can LT3641IUFD#TRPBF generate both 5V and 3.3V outputs simultaneously, and what are the recommended inductor values?
Yes, LT3641IUFD#TRPBF is configured in the typical application to deliver 5V/0.8A (HV channel) and 3.3V/0.5A (LV channel) simultaneously. For 2MHz operation, the datasheet recommends 2.2μH (HV) and 4.7μH (LV) shielded power inductors with ≥2.5A and ≥1.5A saturation current respectively. These values balance size, efficiency (>88% at full load), and transient response. The LT3641IUFD#TRPBF's current-mode control ensures stable operation with these inductors across temperature and input variation.
What is the purpose of the DA pin on LT3641IUFD#TRPBF, and how must it be connected?
The DA (Diode Anode) pin on LT3641IUFD#TRPBF senses current through the external catch diode to implement valley current limiting and protect against shorted outputs. It must be connected directly to the anode of the HV channel's Schottky catch diode. This connection enables the LT3641IUFD#TRPBF to extend the oscillator cycle when diode conduction falls below the valley limit, improving fault robustness. Incorrect DA routing disables this protection, so LT3641IUFD#TRPBF requires strict adherence to the DA-to-diode-anode path shown in the datasheet layout guidelines.
Does LT3641IUFD#TRPBF support synchronization to an external clock, and what are the requirements?
Yes, LT3641IUFD#TRPBF supports external clock synchronization via the SYNC pin (Pin 4), accepting 350kHz–2.5MHz TTL/CMOS signals. The external clock must exceed the internal oscillator frequency by ≥20%, have ≥2V amplitude and ≥40ns pulse width, and be applied only after FB1 rises above 1.165V. The LT3641IUFD#TRPBF ignores SYNC until this condition is met to prevent erratic startup. Once locked, both channels track the external clock, reducing EMI by aligning switching edges - a key advantage for LT3641IUFD#TRPBF in noise-sensitive systems.
LT3641IUFD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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)
LT3641IUFD#TRPBF FAQ
1.How can I place an order for LT3641IUFD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3641IUFD#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 LT3641IUFD#TRPBF reliable?
The price and inventory of LT3641IUFD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3641IUFD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3641IUFD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3641IUFD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3641IUFD#TRPBF?
LT3641IUFD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3641IUFD#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 LT3641IUFD#TRPBF?
For technical support, including LT3641IUFD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3641IUFD#TRPBF requirements.
6.How does Aetrix verify that LT3641IUFD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3641IUFD#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 LT3641IUFD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3641IUFD#TRPBF?
All LT3641IUFD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3641IUFD#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 LT3641IUFD#TRPBF part is unused and in its original packaging.
Return procedure for LT3641IUFD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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