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Analog Devices Inc. LT3685EMSE#PBF
- Part No.:
- LT3685EMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3685EMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,880
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Product details
Overview
LT3685EMSE#PBF from Analog Devices is a 36V, 2A, 2.4MHz monolithic step-down switching regulator with integrated 0.25Ω bipolar NPN switch, internal boost Schottky diode, and overvoltage lockout (36V min, 38V typ) enabling safe 60V transient tolerance. It delivers regulated output from 0.79V to 20V in automotive battery regulation and industrial supply applications.
For engineers reviewing the LT3685EMSE#PBF datasheet, LT3685EMSE#PBF pinout, LT3685EMSE#PBF application, or LT3685EMSE#PBF equivalent, key selection factors include adjustable 200kHz–2.4MHz switching frequency, 0.790V feedback reference, power good flag, soft-start via RUN/SS, and thermal performance in the 10-lead MSOP package with exposed pad.
Technical Context
The LT3685EMSE#PBF implements constant-frequency current-mode control using an external RT resistor to set oscillator frequency between 200kHz and 2.4MHz. Its internal error amplifier drives the VC pin to regulate peak switch current, with active clamp limiting at ~3.5A (duty-cycle dependent).
Operation relies on external boost capacitor and Schottky diode connected to BOOST and BD pins to generate gate drive above VIN, ensuring full saturation of the internal bipolar switch. Power good (PG) asserts when FB reaches 89% of 0.790V, and overvoltage protection disables switching above 36V VIN while sustaining 60V non-repetitive transients.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous operation; withstands 60V transients via OVP shutdown |
| Max Output Current | 2A DC load capability with internal 3.5A switch current limit (min duty cycle) |
| Switching Frequency | Adjustable 200kHz–2.4MHz via RT resistor; supports synchronization to external clock (250kHz–2MHz) |
| Feedback Reference | 0.790V ±10mV over temperature; sets output voltage via resistor divider on FB pin |
| Quiescent Current | <1µA in shutdown (RUN/SS ≤ 0.2V); 450µA typical operating IQ at VIN = 10V |
| Power Good Threshold | Asserts when VOUT reaches 89% of programmed value; open-collector PG output |
| Package Thermal Resistance | θJA = 45°C/W, θJC = 10°C/W in 10-lead MSOP with soldered exposed pad |
Pinout & Package
The LT3685EMSE#PBF is housed in a 10-lead plastic MSOP package with exposed pad (Pin 11), which must be soldered to PCB for thermal and electrical grounding. Package dimensions: 3mm × 3mm body, 0.85mm max height, 0.5mm lead pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost Diode Anode Supply | Connects to anode of external Schottky; supplies bias current to internal regulator when >3V |
| BOOST (2) | Switch Gate Drive Boost | Receives boosted voltage (VIN + Vf) to fully saturate internal bipolar NPN switch |
| SW (3) | Switch Node | Output of internal power switch; connects to inductor, catch diode, and boost capacitor |
| VIN (4) | Main Input Supply | Primary power input (3.6–36V); powers internal regulator and switch; requires local ceramic bypass |
| RUN/SS (5) | Enable & Soft-Start Control | Logic-level enable (≥2.5V = on); RC network here controls output voltage ramp rate |
| SYNC (6) | External Clock Input | Accepts TTL/CMOS clock (250kHz–2MHz) to synchronize switching; ground if unused |
| PG (7) | Power Good Flag | Open-collector output asserting when FB ≥ 89% of 0.790V; valid only if VIN > 3.6V and RUN/SS high |
| FB (8) | Feedback Input | Sense node regulated to 0.790V; connects to resistor divider tap for output voltage programming |
| VC (9) | Error Amplifier Output | Controls peak switch current; external RC network here provides loop compensation |
| RT (10) | Oscillator Frequency Set | Resistor-to-ground sets switching frequency (200kHz–2.4MHz) per datasheet table |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Boost Schottky Diode Driver | Eliminates need for external bootstrap circuitry; enables efficient bipolar switch saturation |
| Overvoltage Lockout Protection | Disables switching at VIN ≥ 36V (min), allowing safe 60V transient survival without external TVS |
| Adjustable Soft-Start | Controlled output voltage ramp via RC network on RUN/SS pin prevents inrush current |
| Current-Mode Control Architecture | Enables fast transient response and inherent cycle-by-cycle current limiting without slope compensation |
| Thermally Enhanced MSOP Package | Exposed pad reduces θJA to 45°C/W; supports 2A continuous output in compact 3mm × 3mm footprint |
Applications
| Automotive Battery Regulation | Industrial Power Supplies |
|---|---|
Use Scenario: Regulating 12V or 24V vehicle battery rail to 3.3V/5V for infotainment ECUs under cold-crank (4.5V) and load-dump (60V) conditions. IC Role / Device Role / Timing Role: Primary buck converter providing isolated, regulated low-voltage rails with OVP-enabled transient robustness. Use Value: Withstands 60V load-dump transients without shutdown or damage; maintains regulation down to 3.6V during cold-crank. | Use Scenario: Distributed 5V/12V regulation in PLC I/O modules where wide input range and EMI-sensitive environments demand high-frequency operation. IC Role / Device Role / Timing Role: High-efficiency, high-frequency step-down regulator minimizing inductor size and conducted noise. Use Value: 2.4MHz operation enables use of 4.7µH inductors and ceramic capacitors, reducing solution size and ripple vs. lower-frequency alternatives. |
| Set-Top Box Power | Wall Transformer Replacement |
Use Scenario: Replacing linear regulators in cable/satellite STB mainboard power trees to improve efficiency and reduce thermal load. IC Role / Device Role / Timing Role: Adjustable-output buck converter delivering 1.2V–5V rails to SoC, memory, and peripherals. Use Value: 0.790V reference and resistor-programmable output support precise voltage scaling; PG flag enables system sequencing. | Use Scenario: Integrated AC/DC replacement in smart home hubs requiring 5V/2A output from unregulated 9–36V DC input (e.g., PoE-powered devices). IC Role / Device Role / Timing Role: Primary DC-DC stage accepting wide-input DC and delivering stable, low-noise output. Use Value: 36V max input and 2A capability eliminate need for pre-regulation; soft-start prevents surge into downstream USB ports. |
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 | Lower 3.1V min input; 1.5A max output; no integrated boost diode; requires external bootstrap | Better suited for low-input, low-power applications; lacks 60V transient tolerance | Select when input never exceeds 30V and board space allows external diode; not drop-in for LT3685EMSE#PBF's high-VIN use cases |
| MP2451DT-LF-Z | 36V max input; 0.6A output; fixed 2MHz frequency; no PG or SYNC; smaller 8-pin SOIC | Targeted at cost-sensitive, low-current consumer applications; no OVP beyond absolute max ratings | Choose only for sub-1A loads where 60V transient immunity and power sequencing are unnecessary |
Compared with LTC3630EMSE#PBF and MP2451DT-LF-Z, the LT3685EMSE#PBF uniquely combines 60V transient survivability, 2A output, integrated boost diode, and programmable frequency-making it the sole option among the three for automotive or industrial 24V/36V systems requiring robustness and flexibility.
Availability
LT3685EMSE#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 extended temperature ranges.
Supply support for LT3685EMSE#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 designs high-performance analog, mixed-signal, and power management ICs for precision signal chain and power conversion applications.
The LT3685EMSE#PBF belongs to the LT® monolithic switching regulator product line, engineered for rugged DC-DC conversion in automotive, industrial, and telecom systems demanding wide input range, transient immunity, and minimal external components.
FAQ
What is the minimum input voltage required for LT3685EMSE#PBF to operate?
The LT3685EMSE#PBF requires a minimum input voltage of 3.6V for continuous operation. Below this threshold, the device ceases switching and cannot maintain regulation. This limit is defined by internal bias circuitry and is independent of switching frequency or load condition. The LT3685EMSE#PBF datasheet specifies 3.6V as the guaranteed minimum under all operating temperatures.
Does LT3685EMSE#PBF require an external Schottky diode?
No, the LT3685EMSE#PBF integrates the boost Schottky diode driver but requires an external Schottky diode connected between BD and BOOST pins. The internal circuitry supplies bias current to the external diode's anode (BD pin) and uses its cathode to generate the boosted gate drive voltage. A discrete Schottky (e.g., DFLS240L) is mandatory for proper switch saturation.
How is the switching frequency set on LT3685EMSE#PBF?
The switching frequency of LT3685EMSE#PBF is set by connecting a resistor from the RT pin to ground. Values range from 8.66kΩ (2.4MHz) to 187kΩ (200kHz), per the datasheet's RT vs. frequency table. The resistor must be placed close to the RT pin with short traces to minimize noise coupling; no capacitor is required on the RT pin.
What is the function of the exposed pad on LT3685EMSE#PBF?
The exposed pad (Pin 11) on LT3685EMSE#PBF is electrically connected to GND and serves dual thermal and electrical functions. It must be soldered directly to a PCB copper pour to achieve the specified θJA = 45°C/W and θJC = 10°C/W. Failure to solder the pad degrades thermal performance and may cause premature thermal shutdown under 2A load.
Can LT3685EMSE#PBF synchronize to an external clock?
Yes, LT3685EMSE#PBF supports external clock synchronization via the SYNC pin (Pin 6). It accepts TTL/CMOS-compatible clocks from 250kHz to 2MHz. The SYNC signal must have rise/fall times faster than 1µs. When not used, SYNC must be grounded; leaving it floating may cause erratic switching behavior or increased EMI.
LT3685EMSE#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
LT3685EMSE#PBF FAQ
1.How can I place an order for LT3685EMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3685EMSE#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 LT3685EMSE#PBF reliable?
The price and inventory of LT3685EMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3685EMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3685EMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3685EMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3685EMSE#PBF?
LT3685EMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3685EMSE#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 LT3685EMSE#PBF?
For technical support, including LT3685EMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3685EMSE#PBF requirements.
6.How does Aetrix verify that LT3685EMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3685EMSE#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 LT3685EMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3685EMSE#PBF?
All LT3685EMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3685EMSE#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 LT3685EMSE#PBF part is unused and in its original packaging.
Return procedure for LT3685EMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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