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Analog Devices Inc. LT3685IMSE#PBF
- Part No.:
- LT3685IMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3685IMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:5,653
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Product details
Overview
LT3685IMSE#PBF from Analog Devices is a 36V, 2A, 2.4MHz monolithic step-down switching regulator with integrated 0.25Ω bipolar NPN switch, boost Schottky diode, and overvoltage lockout (36V min, 38V typ) enabling safe 60V transient tolerance. It delivers regulated 3.3V/5V outputs in automotive battery regulation and industrial supplies.
For engineers reviewing the LT3685IMSE#PBF datasheet, LT3685IMSE#PBF pinout, LT3685IMSE#PBF application, or LT3685IMSE#PBF equivalent, key selection criteria include input voltage range (3.6V–36V), adjustable frequency (200kHz–2.4MHz), soft-start via RUN/SS, power good flag, and thermal performance in the 10-lead MSOP package with exposed pad.
Technical Context
The LT3685IMSE#PBF implements constant-frequency current-mode control with RT-programmable oscillator (200kHz–2.4MHz), internal error amplifier (500 µmho gm), and VC-pin-based peak-current limiting. Its bipolar NPN switch architecture requires external BOOST capacitor and BD-connected Schottky diode for gate drive above VIN.
Operation includes frequency foldback during startup/overload, active VC clamping for current limit, and RUN/SS-controlled soft-start ramp. Power good (PG) asserts when FB reaches 89% of 0.790V reference; overvoltage protection disables switching above 36V–40V VIN, sustaining up to 60V non-repetitive transients.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V operating; withstands 60V transients via OVP shutdown |
| Output Current | 2A continuous; switch current limit 3.2A–4.2A (duty-cycle dependent) |
| Switching Frequency | Adjustable 200kHz–2.4MHz via RT resistor; synchronizable 250kHz–2MHz |
| Feedback Reference | 0.790V ±10mV; enables output voltage setting from 0.79V to 20V |
| Shutdown Current | <1µA at VIN; controlled by RUN/SS pin logic threshold (0.2V low / 2.5V high) |
| Power Good Flag | Open-collector PG asserts when VOUT reaches 89% of programmed value |
| Thermal Package | 10-lead MSOP with exposed GND pad; θJA = 45°C/W, θJC = 10°C/W |
Pinout & Package
LT3685IMSE#PBF uses a thermally enhanced 10-lead MSOP package with exposed pad (Pin 11) soldered to PCB for GND and low thermal resistance. Pin functions are validated per Analog Devices Rev. C datasheet.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost Diode Anode Supply | Connects to Schottky anode; powers internal bias regulator when >3V |
| BOOST (2) | Switch Gate Drive Boost | Provides voltage higher than VIN to fully saturate bipolar NPN switch |
| SW (3) | Switch Output Node | Drives inductor; connects to catch diode cathode and BOOST capacitor |
| VIN (4) | Main Input Supply | Supplies internal regulator and switch; bypass locally with ≥4.7µF ceramic |
| RUN/SS (5) | Enable & Soft-Start Control | Shut down if <0.2V; soft-start ramp generated via external R/C network |
| SYNC (6) | External Clock Input | Accepts 250kHz–2MHz clock; edges <1µs rise/fall for synchronization |
| PG (7) | Power Good Output | Open-collector flag active when FB ≥ 89% of 0.790V; valid if VIN >3.6V and RUN/SS high |
| FB (8) | Feedback Input | Regulated to 0.790V; connects to resistor divider tap for output voltage programming |
| VC (9) | Error Amplifier Output | Controls peak switch current; RC compensation network tied to GND |
| RT (10) | Oscillator Frequency Set | Resistor to GND sets switching frequency (200kHz–2.4MHz) |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Boost Schottky Diode | Eliminates external diode; reduces BOM count and layout area in buck topology |
| Saturating Bipolar NPN Switch | 0.25Ω on-resistance enables high efficiency at 2A load without MOSFET gate drive complexity |
| Overvoltage Lockout (OVP) | Disables switching at VIN ≥36V (min); allows safe operation during 60V automotive load-dump events |
| Programmable Soft-Start | RUN/SS pin accepts external RC network to control output voltage ramp rate and inrush current |
| Current-Mode Control | Enables fast transient response and inherent cycle-by-cycle current limiting without output capacitor ESR dependency |
Applications
| Automotive Battery Regulation | Industrial Power Supplies |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery rail to 3.3V/5V for infotainment ECUs under load-dump conditions. IC Role / Device Role / Timing Role: Primary step-down regulator with 60V transient tolerance and power good signaling for system sequencing. Use Value: Eliminates need for external OVP circuitry; integrated boost diode reduces component count and improves reliability in harsh environments. | Use Scenario: Distributed 5V/12V supply in programmable logic controllers with wide input range and thermal constraints. IC Role / Device Role / Timing Role: High-efficiency DC-DC converter operating from 9–36V industrial input, synchronized to system clock. Use Value: Adjustable 200kHz–2.4MHz frequency allows optimization of inductor size vs. efficiency; MSOP package supports compact board layout. |
| Set-Top Box Power | Wall Transformer Replacement |
Use Scenario: Replacing linear regulators in consumer STB mainboard to reduce heat and improve efficiency at 1A–2A loads. IC Role / Device Role / Timing Role: Compact, low-noise buck converter delivering stable 3.3V/5V from 12V intermediate rail. Use Value: 2.4MHz max frequency enables use of 1µH–4.7µH inductors and small ceramic capacitors, minimizing solution footprint. | Use Scenario: Integrated AC-DC + DC-DC solution where 36V input from offline rectifier feeds directly into LT3685IMSE#PBF. IC Role / Device Role / Timing Role: Final-stage buck regulator accepting up to 36V unregulated DC, providing precise 5V/3.3V output with PG monitoring. Use Value: Wide 3.6V–36V input range eliminates need for pre-regulator; power good flag enables safe microcontroller boot sequencing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3630EMSE#PBF | 40V input, 1.5A, 3mm × 4mm MSOP; no integrated boost diode; requires external Schottky | Lower output current; better suited for space-constrained 1.5A designs without boost diode requirement | Select when lower IOUT suffices and external diode is acceptable for cost or thermal trade-off |
| LM5164QPWPRQ1 | 100V input, 0.6A, SOIC-10; integrated MOSFET; no boost diode; AEC-Q100 qualified | Higher voltage rating but lower current; automotive-qualified; different topology (MOSFET vs. bipolar) | Choose for automotive systems requiring 100V tolerance and AEC-Q100 compliance, not for 2A industrial loads |
Compared with LTC3630EMSE#PBF and LM5164QPWPRQ1, LT3685IMSE#PBF uniquely combines 2A output, integrated boost diode, and 60V transient tolerance in a 10-lead MSOP-making it optimal for cost-sensitive, thermally constrained 36V-input industrial and automotive auxiliary rails where external diode placement is undesirable.
Availability
LT3685IMSE#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial power supplies, set-top box power, and wall transformer replacement requiring stable component supply across temperature and long-term production cycles.
Supply support for LT3685IMSE#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3685IMSE#PBF belongs to the LT® monolithic switching regulator product line, designed specifically for robust, high-voltage DC-DC conversion in harsh environments where input transients, thermal constraints, and minimal external components are critical.
FAQ
What is the maximum input voltage the LT3685IMSE#PBF can safely withstand?
The LT3685IMSE#PBF has overvoltage lockout that disables switching when VIN exceeds 36V (minimum) to 40V (maximum), allowing it to safely withstand non-repetitive 60V transients for up to 1 second. Continuous operation is rated up to 36V, and the absolute maximum rating for VIN is 60V under transient conditions per the datasheet Absolute Maximum Ratings table.
Does the LT3685IMSE#PBF require an external Schottky diode?
No, the LT3685IMSE#PBF integrates a boost Schottky diode on-die, eliminating the need for an external diode in the bootstrap circuit. The BD pin connects directly to the anode of this internal diode, and the BOOST pin uses the resulting voltage to drive the bipolar NPN switch. This integration reduces bill-of-materials count and PCB area.
What is the function of the VC pin on the LT3685IMSE#PBF?
The VC pin on the LT3685IMSE#PBF is the output of the internal error amplifier and controls peak switch current. It serves as the control node for loop compensation-typically connected to ground via an RC network-and features active clamping to implement current limit. Its voltage directly modulates the switch conduction time in current-mode operation.
Can the LT3685IMSE#PBF be synchronized to an external clock?
Yes, the LT3685IMSE#PBF supports external synchronization via the SYNC pin, which accepts clock signals from 250kHz to 2MHz. The SYNC pin has defined logic thresholds (0.5V low, 0.7V high) and requires edge rise/fall times faster than 1µs. When not used, SYNC must be grounded to ensure proper internal oscillator operation.
What package type and thermal characteristics does the LT3685IMSE#PBF use?
The LT3685IMSE#PBF uses a 10-lead plastic MSOP package with exposed pad (Pin 11), specified for –40°C to 125°C operation. Its thermal metrics are θJA = 45°C/W and θJC = 10°C/W, requiring the exposed pad to be soldered to a PCB thermal plane for optimal heat dissipation in 2A continuous operation.
LT3685IMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.6V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.79V
- Voltage - Output (Max):
- 20V
- Current - Output:
- 2A
- Frequency - Switching:
- 200kHz ~ 2.4MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LT3685IMSE#PBF FAQ
1.How can I place an order for LT3685IMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3685IMSE#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 LT3685IMSE#PBF reliable?
The price and inventory of LT3685IMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3685IMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3685IMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3685IMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3685IMSE#PBF?
LT3685IMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3685IMSE#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 LT3685IMSE#PBF?
For technical support, including LT3685IMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3685IMSE#PBF requirements.
6.How does Aetrix verify that LT3685IMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3685IMSE#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 LT3685IMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3685IMSE#PBF?
All LT3685IMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3685IMSE#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 LT3685IMSE#PBF part is unused and in its original packaging.
Return procedure for LT3685IMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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