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Analog Devices Inc. LT3686AEMSE#PBF
- Part No.:
- LT3686AEMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3686AEMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,622
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Product details
Overview
LT3686AEMSE#PBF from Analog Devices (formerly Linear Technology) is a 3.6V–37V input, 1.2A synchronous step-down DC/DC converter in thermally enhanced 12-lead MSOP package with exposed pad. It delivers fixed or adjustable 3.3V/5V output at up to 2.5MHz switching frequency, features internal compensation, boost diode, and BD-pin active load for constant-frequency light-load operation-enabling compact automotive power supplies.
For engineers reviewing the LT3686AEMSE#PBF datasheet, LT3686AEMSE#PBF pinout, LT3686AEMSE#PBF application, or LT3686AEMSE#PBF equivalent, key selection criteria include its 100ns minimum on-time (supporting 16VIN→3.3VOUT @ 2MHz), ±1% FB reference accuracy, 300kHz–2.5MHz programmable frequency, cycle-by-cycle current limit, and robust 60V transient input rating.
Technical Context
The LT3686AEMSE#PBF employs current-mode PWM control with internal bipolar NPN power switch and integrated boost diode. Its oscillator is resistor-programmable (RT pin) and supports external synchronization via SYNC/MODE pin above 0.8V threshold, distinguishing it from the non-synchronizable LT3686.
It implements dual protection: DA-pin valley-current limiting (1.7A) combined with switch peak-current limiting (2.3A typ), plus thermal shutdown, overvoltage lockout (38V typ), and precision UVLO (3.6V). The BD pin enables regulated active load to maintain fixed-frequency operation down to zero load when SYNC/MODE > 0.8V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 37V continuous; withstands 60V transients - supports 24V industrial rails and 12V/24V automotive batteries with cold-crank margin. |
| Output Current | 1.2A continuous - sufficient for powering microcontrollers, sensors, and interface ICs in space-constrained systems. |
| Switching Frequency | 300kHz to 2.5MHz (RT-programmable); >2MHz operation avoids AM band interference - enables use of sub-10µH inductors and <10mm² total solution size. |
| Feedback Reference | 0.795V to 0.815V (±1.25% over temp) - ensures stable 3.3V/5V regulation with minimal output voltage drift across –40°C to 125°C. |
| Quiescent Current | <1µA in shutdown (VEN/UVLO < 0.4V) - preserves battery life in always-on automotive modules and IoT edge nodes. |
| Minimum On-Time | 100ns (typ) - enables high-step-down ratios (e.g., 16V→3.3V) at 2MHz without pulse-skipping, maintaining low audio-band ripple. |
| Package Thermal Resistance | JC = 10°C/W, JA = 40°C/W (MSOP-12 with exposed pad) - allows 1.2A operation at full ambient range without forced airflow. |
Pinout & Package
LT3686AEMSE#PBF is housed in a 12-lead plastic MSOP package with exposed thermal pad (Pin 13 = GND), optimized for high-power density and thermal performance in automotive and industrial applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1, Exposed Pad Pin 13) | Power and signal ground reference | Only ground connection; exposed pad must be soldered to PCB copper pour for thermal and electrical integrity. |
| VIN (Pin 2) | Main input supply | Supplies internal regulator and power switch; requires local 2.2µF ceramic bypass near pin. |
| BD (Pin 3) | Active load control node | When enabled (SYNC/MODE > 0.8V), sinks up to 40mA to maintain fixed-frequency operation at light loads. |
| FB (Pin 4) | Output voltage feedback input | Regulated to 0.8V reference; sets VOUT via resistor divider (R1/R2); R2 ≤ 20kΩ recommended. |
| SS (Pin 5) | Soft-start and tracking control | Internal 2µA current source ramps external capacitor; controls both FB reference and switching frequency ramp-up. |
| RT (Pin 6) | Oscillator frequency programming | Resistor to GND sets frequency from 300kHz to 2.5MHz; 15.4kΩ yields ~2.1MHz typical. |
| EN/UVLO (Pin 7) | Enable and programmable UVLO input | 1.28V threshold enables startup; external resistor divider sets custom turn-on voltage with hysteresis. |
| SYNC/MODE (Pin 8) | External clock sync / BD mode select | Drives sync pulses ≥200ns wide or sets BD active load mode; logic-high (>0.8V) enables fixed-frequency light-load operation. |
| BOOST (Pin 9) | Switch driver bootstrap supply | Charged via internal diode and external capacitor; provides >VIN drive voltage to saturate bipolar NPN switch. |
| DA (Pin 10) | Catch diode anode sense | Monitors valley current in external Schottky diode; triggers frequency foldback if >1.7A to limit fault current. |
| SW (Pin 11) | Switch node | Connects to inductor, catch diode cathode, and BOOST capacitor; carries high di/dt switching current. |
| - (Pin 12) | No connect | Not internally connected; leave unconnected or tie to GND per layout best practice. |
Key Features
| Feature | Design Value |
|---|---|
| Internal boost diode | Eliminates external bootstrap diode, reducing BOM count and PCB area while enabling efficient bipolar switch drive. |
| Constant-frequency light-load operation | BD-pin active load maintains full switching frequency down to zero load - suppresses audible noise and ensures predictable EMI profile. |
| Programmable UVLO with hysteresis | EN/UVLO pin supports custom turn-on voltage (e.g., 9V for automotive) with user-defined hysteresis via resistor divider. |
| Robust fault protection | Cycle-by-cycle current limit (2.3A), DA-pin valley-current foldback (1.7A), thermal shutdown, and 60V transient tolerance ensure reliability in harsh environments. |
| AM-band avoidance | 2.5MHz max frequency places switching harmonics well above 1.6MHz AM radio band - critical for infotainment and ADAS power supplies. |
Applications
| Automotive Infotainment Power Supply | Industrial PLC I/O Module Regulator |
|---|---|
|
Use Scenario: Powers 3.3V SoC, display interface, and CAN transceivers in head-unit under 12V battery with cold-crank (4.5V) and load-dump (60V) conditions. IC Role / Device Role / Timing Role: Primary buck regulator delivering clean, ripple-controlled 3.3V at 1.2A with AM-band immunity and transient robustness. Use Value: 100ns min-on-time enables stable 2MHz operation during cold-crank; 60V transient rating eliminates need for upstream TVS clamping. |
Use Scenario: Generates isolated 5V rail for digital I/O conditioning and fieldbus communication in DIN-rail mounted controllers operating from 24V DC industrial supply. IC Role / Device Role / Timing Role: High-efficiency, thermally robust step-down converter supporting continuous 1.2A load in convection-cooled enclosures. Use Value: MSOP-12 exposed pad achieves 40°C/W θJA, enabling full-rated output without heatsink; internal compensation simplifies layout validation. |
| Portable Medical Sensor Hub | Smart Building Controller Power |
|
Use Scenario: Supplies 3.3V to ultra-low-power MCU, BLE radio, and analog front-end in battery-powered patient monitor with multi-year runtime requirement. IC Role / Device Role / Timing Role: Efficient, low-IQ buck converter with <1µA shutdown current and soft-start to prevent inrush into large capacitive loads. Use Value: Sub-1µA shutdown current extends battery life; SS pin enables controlled power-up sequencing with other system rails. |
Use Scenario: Provides regulated 5V for HVAC controller MCU, RS-485 transceivers, and environmental sensors powered from 24V PoE-derived supply. IC Role / Device Role / Timing Role: Wide-input buck regulator with programmable frequency (1.5MHz) to avoid noise coupling into sensitive analog sensor paths. Use Value: RT-programmable frequency allows EMI tuning; SYNC capability enables deterministic timing alignment with system clock domain. |
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–40V input, 1A output, no BD pin or active load; 3MHz max frequency. | Lacks constant-frequency light-load operation; better suited for higher-frequency, lower-current apps where BD functionality is unnecessary. | Select LTC3630EMSE#PBF only if 1A output suffices and AM-band suppression is less critical than footprint reduction. |
| MP2451DT-LF-Z | 3.3V–36V input, 0.6A output, no SYNC, no BD pin, 2MHz fixed frequency, smaller SOIC-8 package. | Half the output current and no light-load frequency control; lacks programmable UVLO and transient robustness (40V max). | Choose MP2451DT-LF-Z only for cost-sensitive, low-power applications where 600mA is adequate and thermal derating is acceptable. |
Compared with LTC3630EMSE#PBF and MP2451DT-LF-Z, the LT3686AEMSE#PBF uniquely combines 1.2A output, BD-enabled fixed-frequency light-load operation, 60V transient tolerance, and programmable UVLO-making it the only option among the three qualified for demanding automotive and industrial 24V-to-3.3V/5V conversion.
Availability
LT3686AEMSE#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC I/O modules, and portable medical sensor hubs requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3686AEMSE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving aerospace, automotive, industrial, and communications markets.
The LT3686A product line was designed specifically for rugged, wide-input DC/DC conversion in automotive and industrial environments-emphasizing transient robustness, thermal efficiency, and EMI control without external compensation.
FAQ
What is the maximum input voltage rating for LT3686AEMSE#PBF, and how does it handle transients?
The LT3686AEMSE#PBF has an absolute maximum VIN rating of 60V for nonrepetitive one-second transients and 55V for continuous operation. Its overvoltage lockout activates at 38V (typ), protecting downstream circuitry during load-dump events common in 12V/24V automotive systems. This eliminates need for external TVS clamping in most designs.
Can LT3686AEMSE#PBF operate at 2MHz with a 16V input and 3.3V output?
Yes. With a minimum on-time of 100ns (typ), the LT3686AEMSE#PBF supports 16V→3.3V conversion at 2MHz without pulse-skipping. At this ratio, duty cycle is ~22%, requiring only ~220ns on-time - well above the 100ns limit - ensuring stable continuous-mode operation and low output ripple.
How does the BD pin function in LT3686AEMSE#PBF, and what is its design impact?
The BD pin in LT3686AEMSE#PBF enables an internal active load that draws up to 40mA when SYNC/MODE > 0.8V. This maintains full switching frequency at light/no load, eliminating pulse-skipping noise and ensuring predictable EMI behavior - critical for automotive audio and RF-sensitive applications.
Is LT3686AEMSE#PBF pin-compatible with LT3686EMSE#PBF?
No. While both share the same MSOP-12 package and pinout, the LT3686AEMSE#PBF adds external synchronization capability via the SYNC/MODE pin - a feature absent in the LT3686EMSE#PBF. Functionally, they are not drop-in replacements due to differences in MODE pin behavior and BD-pin activation logic.
What thermal performance can be expected from LT3686AEMSE#PBF in a standard 2-layer PCB layout?
In a standard 2-layer PCB with 2oz copper and 200mm² exposed pad copper pour, the LT3686AEMSE#PBF achieves θJA ≈ 40°C/W. At 1.2A load and 12V input, junction temperature rise is ~48°C above ambient - allowing full-rated operation up to +77°C ambient without derating or forced airflow.
LT3686AEMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 12-TSSOP (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):
- 37V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 37V
- Current - Output:
- 1.2A
- Frequency - Switching:
- 300kHz ~ 2.5MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 12-MSOP-EP
LT3686AEMSE#PBF FAQ
1.How can I place an order for LT3686AEMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3686AEMSE#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 LT3686AEMSE#PBF reliable?
The price and inventory of LT3686AEMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3686AEMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3686AEMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3686AEMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3686AEMSE#PBF?
LT3686AEMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3686AEMSE#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 LT3686AEMSE#PBF?
For technical support, including LT3686AEMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3686AEMSE#PBF requirements.
6.How does Aetrix verify that LT3686AEMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3686AEMSE#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 LT3686AEMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3686AEMSE#PBF?
All LT3686AEMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3686AEMSE#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 LT3686AEMSE#PBF part is unused and in its original packaging.
Return procedure for LT3686AEMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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