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Analog Devices Inc. LT3685EMSE#TRPBF
- Part No.:
- LT3685EMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3685EMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,459
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Product details
Overview
LT3685EMSE#TRPBF 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 LT3685EMSE#TRPBF datasheet, LT3685EMSE#TRPBF pinout, LT3685EMSE#TRPBF application, or LT3685EMSE#TRPBF 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#TRPBF uses constant-frequency current-mode control with RT-pin programmable oscillator (200kHz–2.4MHz), internal error amplifier (500µmho gm), and VC pin for peak-current loop control. Its bipolar NPN switch features 0.25Ω on-resistance and 3.2A–4.2A current limit depending on duty cycle.
Overvoltage protection disables switching above 38V typical VIN while sustaining 60V transients; bias can be supplied from BD pin (>3V) to improve efficiency. The device supports external synchronization (250kHz–2MHz) and includes frequency foldback during startup/overload.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous operation; withstands 60V nonrepetitive transients via OVP |
| Output Current | 2A maximum continuous output; 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 over temperature; enables precise output voltage setting from 0.79V to 20V |
| Shutdown Current | <1µA at VIN when RUN/SS ≤ 0.2V; ensures ultra-low system standby power |
| Power Good Flag | Open-collector PG asserts high when FB reaches 89% of target; valid only if VIN > 3.6V and RUN/SS high |
| Thermal Package | 10-lead MSOP with exposed pad (JA = 45°C/W, JC = 10°C/W); requires PCB soldering for thermal performance |
Pinout & Package
The LT3685EMSE#TRPBF is housed in a 10-lead plastic MSOP package with exposed pad (Pin 11), which must be soldered to PCB ground for thermal management and electrical integrity.
| 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 Drive Voltage Source | Provides >VIN voltage to fully saturate internal bipolar NPN switch; requires external boost capacitor/diode |
| SW (3) | Internal Switch Output | Drives inductor and catch diode; connects to boost capacitor; carries full switching current |
| VIN (4) | Main Input Power | Supplies internal regulator and switch; bypass locally with ≥4.7µF ceramic; max 60V transient rating |
| RUN/SS (5) | Enable & Soft-Start Control | ≤0.2V = shutdown (<1µA IQ); ≥2.5V = active; RC network here sets output voltage ramp rate |
| SYNC (6) | External Clock Input | Accepts TTL/CMOS clock edges (rise/fall <1µs); grounds when unused; range 250kHz–2MHz |
| PG (7) | Power Good Open-Collector | Sinks current until FB reaches 89% of target; requires external pull-up; valid only above 3.6V VIN |
| FB (8) | Feedback Input | Regulated to 0.790V; connects to resistor divider tap; bias current flows out (7–30nA) |
| VC (9) | Error Amplifier Output | Controls peak switch current; RC network to ground sets loop compensation; clamped to RUN/SS during soft-start |
| RT (10) | Oscillator Frequency Set | Resistor to ground sets switching frequency (200kHz–2.4MHz); 8.66kΩ = 2.4MHz, 187kΩ = 200kHz |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Boost Schottky Diode | Eliminates external boost diode; reduces BOM count and layout area while maintaining efficient switch drive |
| Saturating Bipolar NPN Switch | 0.25Ω on-resistance enables high efficiency at 2A load without requiring MOSFET gate drivers or external FETs |
| Overvoltage Lockout Protection | Disables switching at VIN ≥36V (min); allows safe operation under 60V automotive load-dump transients |
| Programmable Soft-Start | RUN/SS pin accepts RC network to control output voltage ramp rate, preventing inrush current and overshoot |
| Current-Mode Control Architecture | Enables fast transient response and inherent cycle-by-cycle current limiting without requiring output capacitor ESR |
Applications
| Automotive Battery Regulation | Industrial Power Supplies |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery rails to 3.3V/5V for infotainment ECUs and ADAS sensors under load-dump conditions. IC Role / Device Role / Timing Role: Primary DC/DC step-down regulator with OVP protection and 60V transient tolerance. Use Value: Eliminates need for external TVS or discrete OVP circuitry; maintains regulation during cold-crank (≥3.6V) and load-dump (≤60V). | Use Scenario: Providing stable 5V/12V auxiliary power in PLC I/O modules and motor drives operating from unregulated 24V–36V industrial rails. IC Role / Device Role / Timing Role: High-input-voltage buck converter with adjustable frequency to avoid noise-sensitive bands. Use Value: 2.4MHz max switching enables use of 4.7µH inductors and 22µF ceramic output caps, minimizing solution size in space-constrained enclosures. |
| Set-Top Box Power | Distributed Wall Adapter Regulation |
Use Scenario: Generating 3.3V core and 1.2V DDR memory rails from 12V wall adapter input in consumer STB platforms. IC Role / Device Role / Timing Role: Secondary buck regulator delivering low-noise, tightly regulated outputs with soft-start sequencing. Use Value: Power good flag enables controlled enable sequencing of downstream LDOs; <1µA shutdown current meets Energy Star standby requirements. | Use Scenario: Replacing linear regulators in multi-output wall adapters to improve efficiency and reduce heat in compact housings. IC Role / Device Role / Timing Role: High-efficiency primary buck stage stepping down 36V adapter output to intermediate 5V/12V rails. Use Value: Integrated boost diode and 0.25Ω switch deliver >90% efficiency at 2A, reducing thermal derating and enabling smaller heatsinks or no heatsink. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#TRPBF | 40V input, 1.5A output, 3mm × 4mm MSOP; no integrated boost diode; requires external bootstrap cap | Lower current capability; better suited for low-power industrial sensors than high-current STB rails | Select when lower quiescent current (12µA) and tighter VREF (0.8V ±0.5%) outweigh need for 2A output |
| MP2451DT-LF-Z | 36V input, 0.6A output, 8-pin SOIC; no OVP; no PG flag; fixed 2.2MHz frequency | Limited to sub-1A loads; lacks transient protection and power sequencing signals | Select for cost-sensitive, low-current applications where 60V transient immunity and PG signaling are not required |
Compared with LTC3631EMSE#TRPBF and MP2451DT-LF-Z, the LT3685EMSE#TRPBF uniquely combines 2A output, integrated boost diode, 60V transient tolerance, and power good flag in a thermally enhanced MSOP-making it optimal for automotive and industrial 2A buck applications demanding robustness and design simplicity.
Availability
LT3685EMSE#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial power supplies, set-top box power, and distributed wall adapter regulation requiring stable component supply across extended temperature ranges.
Supply support for LT3685EMSE#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, industrial automation, and automotive markets.
The LT3685EMSE#TRPBF belongs to Analog Devices' Power by Linear™ family of monolithic DC/DC regulators, designed specifically for high-input-voltage industrial and automotive applications requiring robust transient protection and minimal external components.
FAQ
What is the absolute maximum input voltage rating for LT3685EMSE#TRPBF?
The LT3685EMSE#TRPBF has an absolute maximum VIN rating of 60V for nonrepetitive 1-second transients, with continuous operation limited to 40V. Its overvoltage lockout activates at 36V minimum (38V typical), disabling switching to protect the internal circuitry while sustaining the 60V transient without damage.
Does LT3685EMSE#TRPBF require an external boost diode?
No, the LT3685EMSE#TRPBF integrates a boost Schottky diode on-die, eliminating the need for an external diode. The BD pin connects directly to the anode of this internal diode, and the BOOST pin uses the resulting voltage to fully saturate the internal bipolar NPN switch-reducing component count and board area.
How is the switching frequency set on LT3685EMSE#TRPBF?
The switching frequency of LT3685EMSE#TRPBF is set by connecting a resistor from the RT pin to ground. Values range from 8.66kΩ (2.4MHz) to 187kΩ (200kHz). The device also supports external synchronization between 250kHz and 2MHz via the SYNC pin, allowing noise-sensitive systems to avoid interference bands.
What thermal considerations apply to LT3685EMSE#TRPBF in the MSOP package?
The LT3685EMSE#TRPBF in the 10-lead MSOP package features an exposed pad (Pin 11) that must be soldered to a PCB ground plane. This achieves θJA = 45°C/W and θJC = 10°C/W. Without proper pad soldering, thermal resistance increases significantly, risking junction temperature exceedance at 2A load and ambient >85°C.
Can LT3685EMSE#TRPBF operate with input voltage below 3.6V?
No, the LT3685EMSE#TRPBF requires a minimum input voltage of 3.6V to operate. Below this threshold, the internal regulator cannot sustain bias, causing loss of regulation and invalidation of the power good flag. Startup is guaranteed only above 3.6V, and PG assertion requires both VIN > 3.6V and RUN/SS high.
LT3685EMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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#TRPBF FAQ
1.How can I place an order for LT3685EMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3685EMSE#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 LT3685EMSE#TRPBF reliable?
The price and inventory of LT3685EMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3685EMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3685EMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3685EMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3685EMSE#TRPBF?
LT3685EMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3685EMSE#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 LT3685EMSE#TRPBF?
For technical support, including LT3685EMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3685EMSE#TRPBF requirements.
6.How does Aetrix verify that LT3685EMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3685EMSE#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 LT3685EMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3685EMSE#TRPBF?
All LT3685EMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3685EMSE#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 LT3685EMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3685EMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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