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Analog Devices Inc. LT3641IFE#PBF
- Part No.:
- LT3641IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3641IFE#PBF.pdf
- Description:
- IC REG BUCK ADJ DL 28TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,206
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Product details
Overview
LT3641IFE#PBF from Analog Devices (formerly Linear Technology) is a dual-channel monolithic buck switching regulator with integrated power-on reset and window-mode watchdog timer. It delivers 5V/0.8A and 3.3V/0.5A outputs, operates across 4V–42V (HV channel) and 2.5V–5.5V (LV channel), and supports adjustable 350kHz–2.5MHz synchronization - used in automotive ECU power rails requiring transient-robust dual-rail sequencing.
For engineers reviewing the LT3641IFE#PBF datasheet, LT3641IFE#PBF pinout, LT3641IFE#PBF application, or LT3641IFE#PBF equivalent, key selection criteria include its dual-buck architecture with independent soft-start, programmable POR/watchdog timing via external capacitors, input transient protection to 55V, and thermal-enhanced 28-pin TSSOP package with exposed GND pad.
Technical Context
The LT3641IFE#PBF integrates two current-mode PWM controllers sharing a single adjustable oscillator. The high-voltage channel uses a nonsynchronous NPN switch with internal 2.4A top switch and catch-diode current sensing (DA pin); the low-voltage channel employs fully synchronous MOSFETs with PMOS/NMOS current limits of 1.9A/1.6A respectively.
Its power-on reset asserts until FB1 exceeds 1.165V (HV) and FB2 exceeds 550mV (LV), both timed by CPOR capacitor; the window-mode watchdog monitors WDI pulse edges using CWDT capacitor, triggering WDO if intervals fall outside tWDL = 2.0ms or tWDU = 32ms (at CWDT = 820pF).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| HV Input Range | 4V to 42V continuous, with 55V nonrepetitive transient protection - enables direct connection to 24V automotive battery without external TVS. |
| LV Input Range | 2.5V to 5.5V - supports direct tie to HV output or separate 3.3V/5V rail for two-stage regulation. |
| Switching Frequency | 350kHz to 2.5MHz, set by RT resistor or external SYNC signal - allows optimization of inductor size vs. efficiency (e.g., 2MHz → 2.2μH HV inductor). |
| FB1 Reference Voltage | 1.265V ±15mV over temperature - sets HV output via resistor divider; enables precise 5V (R2/R1 = 2.95) or 3.3V (R2/R1 = 1.61) regulation. |
| FB2 Reference Voltage | 600mV ±15mV over temperature - sets LV output; supports 1.2V (R4/R3 = 1.0), 1.8V (R4/R3 = 2.0), or 3.3V (R4/R3 = 4.5) with standard 1% resistors. |
| Quiescent Current | 290μA typical at VIN = 12V - maintains low standby loss in always-on automotive modules. |
| Thermal Package | 28-pin TSSOP with exposed GND pad (θJC = 8°C/W) - enables >2W dissipation at ≤125°C junction under forced air. |
Pinout & Package
LT3641IFE#PBF is housed in a thermally enhanced 28-lead plastic TSSOP package (FE) with exposed GND pad (Pin 29), rated for –40°C to +125°C operating junction temperature. The package provides low thermal resistance (θJA = 30°C/W) and requires soldering of the exposed pad to PCB ground for optimal thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1 (Pin 6) | HV feedback reference node | Regulated to 1.265V; connects to resistor divider tap for output voltage setting - determines HV rail accuracy and load regulation. |
| FB2 (Pin 1) | LV feedback reference node | Regulated to 600mV; connects to LV divider tap - enables stable 1.2V–3.3V outputs with <±1% initial error. |
| EN/UVLO (Pin 3) | Global enable & UVLO input | 1.26V threshold with 2μA hysteresis current - allows programmable VIN undervoltage lockout (e.g., disable below 9V battery). |
| RST1 (Pin 9) | HV power-on reset output | Open-drain, active-low; released after CPOR timeout when FB1 > 1.165V - sequences microcontroller reset after HV rail stabilizes. |
| WDO (Pin 10) | Watchdog timeout flag | Open-drain, active-low; asserts if WDI pulses violate window (tWDL/tWDU) - triggers system reset on MCU hang or timing fault. |
| SW1 (Pin 19) | HV switch node | Connects to HV inductor and catch diode cathode - carries full HV switching current; requires low-inductance layout to minimize EMI. |
| VIN2 (Pin 24) | LV input supply | Accepts 2.5V–5.5V; powers LV channel and internal bias - can be tied to HV output for compact two-stage design. |
| GND (Pins 15,16,23,26,29) | Power & signal ground | Multiple dedicated pins + exposed pad - must be solidly connected to PCB ground plane to ensure stability and thermal performance. |
Key Features
| Feature | Design Value |
|---|---|
| Independent soft-start control | SS1 and SS2 pins allow separate RC ramp timing for HV/LV outputs - prevents inrush current and enables controlled power-up sequencing. |
| Window-mode watchdog timer | Monitors WDI pulse timing boundaries (tWDL/tWDU) - detects both stuck-at-high/low and excessive jitter in MCU watchdog signals. |
| Burst Mode® operation | Maintains <15mVpp output ripple at light loads while sustaining >85% efficiency - eliminates audible noise and extends battery life in standby mode. |
| Cycle-by-cycle current limit | SW1 peak limit = 2.8A typ, SW2 PMOS/NMOS limits = 1.9A/1.6A - protects against shorted outputs without external sense resistors. |
| Input transient protection | Withstands 55V/1s transients per Absolute Maximum Ratings - eliminates need for upstream TVS in 24V automotive systems. |
Applications
| Automotive ECU Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: Dual-rail power for 32-bit MCU (5V core logic) and analog sensor interface (3.3V ADC, DAC, op-amps) in engine control unit. IC Role / Device Role / Timing Role: Primary DC/DC converter providing sequenced, regulated 5V/0.8A and 3.3V/0.5A rails with POR and watchdog supervision. Use Value: Eliminates discrete reset IC and external watchdog circuit; 55V transient tolerance avoids external TVS diodes on 24V battery input. | Use Scenario: Compact dual-output supply for isolated digital I/O expansion module with FPGA, level translators, and isolated RS-485 transceivers. IC Role / Device Role / Timing Role: Single-chip solution generating 3.3V for FPGA core and 5V for bus drivers, with independent soft-start to prevent backfeeding. Use Value: Reduces BOM count by 4+ components (two regulators, POR, watchdog, soft-start caps); TSSOP package fits tight 12mm × 12mm board area. |
| Medical Patient Monitor | Test & Measurement Equipment |
Use Scenario: Low-noise dual-rail supply for ECG front-end (3.3V precision analog) and ARM Cortex-M7 processor (5V I/O, 1.2V core via secondary LDO). IC Role / Device Role / Timing Role: Main switching regulator delivering clean, sequenced rails; Burst Mode® ensures <20μA quiescent draw during sleep mode. Use Value: Meets IEC 60601 leakage current requirements via sub-1μA shutdown current and low EMI in Burst Mode. | Use Scenario: Benchtop oscilloscope auxiliary supply powering 12-bit ADC reference (3.3V) and FPGA configuration memory (5V) from 12V wall adapter. IC Role / Device Role / Timing Role: High-efficiency dual-buck regulator with SYNC input locked to system clock - reduces beat-frequency noise in sensitive analog measurements. Use Value: Adjustable 2MHz switching frequency enables use of small 2.2μH/4.7μH shielded inductors, minimizing board footprint and magnetic coupling to analog sections. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3641EFE#PBF | Same silicon, –40°C to +125°C grade (E-grade), lower production test coverage than I-grade. | Suitable for commercial/industrial environments without extended temp validation needs. | Select when full automotive qualification not required and cost sensitivity outweighs guaranteed 125°C operation. |
| LT3645IFE#PBF | Single-channel 42V buck with integrated 3.3V LDO (200mA), no watchdog/POR, different pinout. | Lacks dual-output capability and system supervision functions - only replaces HV channel. | Choose only if LV rail is supplied separately and watchdog/POR are implemented externally. |
Compared with LTC3641EFE#PBF, LT3641IFE#PBF guarantees full –40°C to +125°C operation with extended test coverage; compared with LT3645IFE#PBF, it provides true dual-output regulation with integrated supervision, eliminating four discrete components but requiring larger PCB area.
Availability
LT3641IFE#PBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial PLC I/O modules, and medical patient monitors requiring stable component supply with guaranteed 125°C operation and long-term lifecycle support.
Supply support for LT3641IFE#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 and maintains full product support, datasheets, and application engineering for legacy Linear parts including the LT3641 series.
The LT3641IFE#PBF belongs to Linear's high-voltage monolithic buck regulator family, designed specifically for automotive and industrial applications demanding robust input transient handling, precise power sequencing, and integrated system-level supervision.
FAQ
What is the maximum input voltage rating for LT3641IFE#PBF, and how does it handle transients?
The LT3641IFE#PBF has an absolute maximum VIN rating of 55V for nonrepetitive 1-second transients, with continuous operation rated up to 42V. Its internal circuitry includes input transient protection that clamps energy without latch-up or damage, enabling direct connection to 24V automotive batteries without external TVS diodes - a key advantage over standard 40V-rated buck regulators. This protection is inherent to the process and layout, not dependent on external components.
How do the RST1 and RST2 outputs differ in timing and function on LT3641IFE#PBF?
RST1 and RST2 are independent open-drain reset outputs on LT3641IFE#PBF, each triggered by its respective feedback rail: RST1 releases after CPOR timeout when FB1 exceeds 1.165V (HV channel), while RST2 releases when FB2 exceeds 550mV (LV channel). Their timeout periods are identical and set solely by the CPOR capacitor value - allowing precise, decoupled sequencing of MCU core and peripheral power domains without external timers.
Can LT3641IFE#PBF operate with only the HV channel enabled while the LV channel remains inactive?
Yes, LT3641IFE#PBF supports independent channel control: the LV channel is disabled by pulling EN2 below its 1.13V threshold, while the HV channel continues regulating normally if EN/UVLO is high and VIN is within range. In this state, the LV section draws <1μA, and SW2 remains static - enabling flexible power tree design where the 3.3V rail is only activated after the 5V rail is stable, as verified in the Functional Block Diagram and EN2 electrical characteristics table.
What is the purpose of the DA pin on LT3641IFE#PBF, and how must it be connected?
The DA (Diode Anode) pin on LT3641IFE#PBF senses catch-diode current for valley-current limiting and fault protection in the HV nonsynchronous buck stage. It must be connected directly to the anode of the external Schottky catch diode (e.g., D1 in Typical Application TA01a). This connection enables active valley-current foldback during overload or short-circuit conditions - a critical safety feature not present in basic current-mode controllers - and is required for robust operation above 1A load.
Does LT3641IFE#PBF support synchronization to an external clock, and what are the constraints?
Yes, LT3641IFE#PBF supports external synchronization via the SYNC pin (Pin 4), accepting 350kHz–2.5MHz TTL/CMOS clock signals with ≥2V amplitude and ≥40ns pulse width. The internal oscillator frequency (set by RT) must be at least 20% lower than the lowest expected SYNC frequency to avoid erratic behavior. Synchronization is ignored until FB1 rises above 1.165V, ensuring stable locking only after HV rail startup - a safeguard confirmed in the Timing Diagrams and Applications Information sections.
LT3641IFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-TSSOP (0.173", 4.40mm Width) 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-TSSOP-EP
LT3641IFE#PBF FAQ
1.How can I place an order for LT3641IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3641IFE#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 LT3641IFE#PBF reliable?
The price and inventory of LT3641IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3641IFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3641IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3641IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3641IFE#PBF?
LT3641IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3641IFE#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 LT3641IFE#PBF?
For technical support, including LT3641IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3641IFE#PBF requirements.
6.How does Aetrix verify that LT3641IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3641IFE#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 LT3641IFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3641IFE#PBF?
All LT3641IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3641IFE#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 LT3641IFE#PBF part is unused and in its original packaging.
Return procedure for LT3641IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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