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Analog Devices Inc. LT3640IUFD#PBF
- Part No.:
- LT3640IUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT3640IUFD#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.1A/1.3A 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,862
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Product details
Overview
LT3640IUFD#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 1.3A from its high-voltage nonsynchronous channel (4V–35V input, 3.3V/0.8A typical output) and 1.1A from its low-voltage synchronous channel (2.5V–5.5V input, 1.8V/0.8A typical output), operating at adjustable 350kHz–2.5MHz frequency. It is used in automotive ECU power rails requiring fault-tolerant dual-output regulation.
For engineers reviewing the LT3640IUFD#PBF datasheet, LT3640IUFD#PBF pinout, LT3640IUFD#PBF application, or LT3640IUFD#PBF equivalent, key selection criteria include programmable reset timeout (via CPOR), windowed watchdog timing (via CWDT), Burst Mode® operation for light-load efficiency, and thermal performance in the 4mm × 5mm QFN package with exposed pad.
Technical Context
The LT3640IUFD#PBF integrates two independent current-mode buck regulators sharing a single adjustable oscillator. The high-voltage channel uses an internal 2.4A NPN top switch with 36.5V OVLO and supports nonsynchronous operation with external catch diode; the low-voltage channel employs internal synchronous MOSFETs (PMOS/NMOS) with 1.5A/1.2A current limits and no external diode required.
Its power-on reset and watchdog functions are capacitor-programmable: CPOR sets both RST1/RST2 assertion time and WDO timeout, while CWDT configures watchdog upper/lower boundaries (e.g., 27ms/1.68ms typical with 820pF). The device enters low-ripple Burst Mode® below ~200mA load to maintain >85% efficiency at light loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range (HV) | 4V to 35V - supports wide automotive battery range; OVLO at 36.5V prevents damage during load dump transients up to 55V for 1 second. |
| Input Voltage Range (LV) | 2.5V to 5.5V - enables direct connection to HV output (e.g., 3.3V rail) or separate low-voltage supply for logic cores. |
| Switching Frequency | 350kHz to 2.5MHz - set by RT resistor; higher frequencies allow smaller magnetics (e.g., 3.3µH at 2MHz for 3.3V output). |
| Quiescent Current | 290µA typical - enables always-on subsystems without excessive standby drain; drops to <1µA in shutdown. |
| Output Accuracy (FB1/FB2) | ±1.2% (1.265V) / ±2% (600mV) - ensures tight regulation of critical MCU I/O and core voltages across temperature. |
| Thermal Resistance (θJC) | 2.7°C/W - achieved via exposed pad soldered to PCB ground plane; enables 1.3A/1.1A continuous output without forced air. |
Pinout & Package
The LT3640IUFD#PBF is housed in a thermally enhanced 28-lead (4mm × 5mm) plastic QFN package with exposed pad (Pin 29), which must be soldered to PCB ground for optimal thermal performance (θJA = 34°C/W, θJC = 2.7°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW1 (Pin 16) | High-voltage switch node | Connects to inductor and cathode of external catch diode; carries full HV channel switching current and voltage stress. |
| VIN (Pin 19) | High-voltage input supply | Primary power source for internal circuitry and HV channel; requires local ceramic bypassing near pin. |
| VIN2 (Pin 21) | Low-voltage input supply | Feeds LV channel and auxiliary bias; can be tied to HV output for cascaded regulation or powered separately. |
| FB1 (Pin 3) | HV feedback reference input | Regulated to 1.265V; sets VOUT1 via resistor divider; accuracy directly determines output voltage tolerance. |
| FB2 (Pin 1) | LV feedback reference input | Regulated to 600mV; sets VOUT2 via resistor divider; lower reference enables precise 1.2V/1.8V core rail generation. |
| RST1/RST2 (Pins 6/5) | Open-drain reset outputs | Assert low until respective FB pin reaches threshold + timeout (CPOR); drive microcontroller reset inputs directly. |
| WDO/WDI (Pins 7/11) | Watchdog output/input | WDO asserts on window violation; WDI accepts µP pulses with ≥300ns min width and 0.55–1.15V threshold. |
| CPOR (Pin 9) | Reset/watchdog timing capacitor | Single capacitor programs RST1/RST2 timeout (e.g., 9.5ms typical with 220pF) and WDO assertion period. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable window-mode watchdog | Prevents system lockup by detecting µP pulse timing violations (too close/too far apart) using CWDT capacitor-enables fail-safe recovery in automotive ECUs. |
| Independent soft-start control (SS1/SS2) | Capacitor-based ramp control for each channel allows staggered startup sequencing and voltage tracking between rails-critical for FPGA or multi-core SoC power sequencing. |
| Synchronous LV channel with integrated MOSFETs | Eliminates external Schottky diode, reducing BOM count and conduction losses-improves efficiency by ~5% at 1A load vs. nonsynchronous alternatives. |
| Burst Mode® operation | Maintains >85% efficiency down to ~25mA load while limiting output ripple to <20mVP-P-ideal for always-on sensor nodes with intermittent activity. |
| Overvoltage lockout (36.5V) | Disables switching before internal stress limits are exceeded, enabling robust operation during ISO 7637-2 pulse 5a (load dump) events-meets AEC-Q100 stress requirements. |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering microcontroller, CAN transceiver, and analog front-end from 12V battery with transient immunity. IC Role / Device Role / Timing Role: Dual-output DC/DC regulator providing isolated 3.3V (MCU I/O) and 1.8V (core logic) rails with coordinated power-on reset and watchdog supervision. Use Value: Single-chip solution reduces board area by 40% vs. discrete regulators; OVLO and Burst Mode® ensure reliable operation during cold-crank (4.5V) and load-dump (55V) conditions. | Use Scenario: Generating stable 3.3V and 1.8V supplies for field-programmable gate array (FPGA) and ADC in modular I/O base. IC Role / Device Role / Timing Role: Primary power management IC delivering sequenced, regulated outputs with programmable soft-start and fault detection. Use Value: SS1/SS2 pins enable precise voltage ramp alignment between rails; PGOOD flag confirms both outputs are in regulation before FPGA configuration begins. |
| Medical Patient Monitor Sensor Hub | Telecom Remote Radio Unit (RRU) |
Use Scenario: Powering low-noise analog signal chain (ADC, op-amps) and ARM Cortex-M4 processor from 5V USB or backup battery. IC Role / Device Role / Timing Role: High-efficiency dual buck converter with ultra-low quiescent current and low-output-ripple Burst Mode® for battery longevity. Use Value: 290µA IQ extends battery life >3× vs. standard PWM regulators; 2.7°C/W θJC enables passive cooling in sealed enclosures. | Use Scenario: Providing bias rails for RF power amplifiers and digital baseband ASIC in outdoor wireless infrastructure. IC Role / Device Role / Timing Role: Robust dual-regulator with wide input range (4V–35V) and thermal resilience for unregulated solar/battery hybrid inputs. Use Value: Exposed-pad QFN package sustains 125°C junction temperature; OVLO prevents latch-up during lightning-induced surges on remote power feeds. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3641IUFD#PBF | Same pinout and package; HV channel rated for 1.5A (vs. 1.3A), LV channel unchanged; higher peak current capability. | Better suited for applications requiring margin above 1.3A HV load, e.g., powering multiple peripherals from 3.3V rail. | Select LT3641IUFD#PBF when HV output current demand exceeds 1.3A but layout reuse is required. |
| TPS54290PWPR | Single-channel, 2A synchronous buck; no integrated watchdog/reset; requires external supervisor IC for similar functionality. | Lacks native power-on reset and window watchdog; demands additional components for safety-critical timing functions. | Choose only if dual-output integration is not required and cost-per-rail optimization outweighs feature loss. |
Compared with LT3641IUFD#PBF, the LT3640IUFD#PBF offers lower HV current rating but identical footprint and feature set-ideal for cost-sensitive designs within 1.3A limit. Versus TPS54290PWPR, it provides integrated safety timers and dual regulation at the expense of higher unit cost and fixed topology.
Availability
LT3640IUFD#PBF is available at Aetrix Electronics and suitable for automotive electronic control units, industrial PLC modules, and medical sensor hubs requiring stable component supply, extended temperature operation (–40°C to 125°C), and AEC-Q100-aligned reliability.
Supply support for LT3640IUFD#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 semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3640IUFD#PBF belongs to ADI's Power by Linear™ portfolio of monolithic DC/DC converters designed specifically for demanding automotive, industrial, and medical systems requiring high integration, fault tolerance, and thermal resilience.
FAQ
What is the maximum input voltage the LT3640IUFD#PBF can withstand without damage?
The LT3640IUFD#PBF features an overvoltage lockout (OVLO) threshold of 36.5V, which disables switching to protect internal circuitry. It can sustain non-repetitive 55V transients for up to one second without damage, making it suitable for automotive load-dump conditions per ISO 7637-2. Continuous operation must remain ≤35V.
How do I configure the power-on reset timeout for the LT3640IUFD#PBF?
The power-on reset timeout for both channels of the LT3640IUFD#PBF is set by a single capacitor on the CPOR pin (Pin 9). A 220pF capacitor yields a typical timeout of 9.5ms. The RST1 and RST2 outputs remain asserted low until FB1 exceeds 1.165V and FB2 exceeds 550mV, respectively, then hold for the CPOR-determined duration.
Does the LT3640IUFD#PBF require an external catch diode for the high-voltage channel?
Yes, the LT3640IUFD#PBF high-voltage channel is nonsynchronous and requires an external Schottky catch diode connected between SW1 and GND. The DA pin (Pin 15) senses diode anode current for valley-current limiting. No external diode is needed for the low-voltage synchronous channel, which integrates both PMOS and NMOS switches.
Can the LT3640IUFD#PBF operate with different switching frequencies on each channel?
No-the LT3640IUFD#PBF uses a single shared oscillator for both channels, set by the RT resistor (Pin 7) or external SYNC signal (Pin 4). Both regulators are inherently synchronized; independent frequency control is not supported. The RT value determines the base frequency (350kHz–2.5MHz), and SYNC must be ≥20% higher than the internal frequency to avoid erratic behavior.
What thermal design considerations apply to the LT3640IUFD#PBF in its QFN package?
The LT3640IUFD#PBF's 4mm × 5mm QFN package features an exposed thermal pad (Pin 29) that must be soldered to a large PCB copper area connected to ground. With θJC = 2.7°C/W, proper pad layout enables junction temperatures ≤125°C at full 1.3A/1.1A load without forced airflow. Thermal vias under the pad (≥6× 0.3mm) are strongly recommended to transfer heat to inner layers.
LT3640IUFD#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):
- 35V
- Voltage - Output (Min/Fixed):
- 0.6V, 1.265V
- Voltage - Output (Max):
- 33.97V
- Current - Output:
- 1.1A, 1.3A
- Frequency - Switching:
- 500kHz ~ 2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LT3640IUFD#PBF FAQ
1.How can I place an order for LT3640IUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3640IUFD#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 LT3640IUFD#PBF reliable?
The price and inventory of LT3640IUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3640IUFD#PBF is usually 5 days.
3.What payment methods are accepted for LT3640IUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3640IUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3640IUFD#PBF?
LT3640IUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3640IUFD#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 LT3640IUFD#PBF?
For technical support, including LT3640IUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3640IUFD#PBF requirements.
6.How does Aetrix verify that LT3640IUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3640IUFD#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 LT3640IUFD#PBF meets industry standards.
7.What is the process for return or replacement of LT3640IUFD#PBF?
All LT3640IUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3640IUFD#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 LT3640IUFD#PBF part is unused and in its original packaging.
Return procedure for LT3640IUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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