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Analog Devices Inc. LT3686AIMSE#PBF
- Part No.:
- LT3686AIMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3686AIMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,216
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Product details
Overview
LT3686AIMSE#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. It delivers regulated 3.3V or 5V output with adjustable switching frequency up to 2.5MHz, internal compensation, and active load control via BD pin for fixed-frequency operation at light loads-ideal for automotive infotainment power rails and industrial 24V-to-3.3V conversion.
For engineers reviewing the LT3686AIMSE#PBF datasheet, LT3686AIMSE#PBF pinout, LT3686AIMSE#PBF application, or LT3686AIMSE#PBF equivalent, key selection criteria include its 100ns minimum on-time enabling high VIN/VOUT ratios at 2MHz, ±1% FB reference accuracy over temperature, integrated boost diode, and SYNC/MODE dual-function pin supporting external clock synchronization and BD active load enable/disable.
Technical Context
The LT3686AIMSE#PBF employs current-mode PWM control with cycle-by-cycle current limiting, thermal shutdown, and DA-pin-based valley-current foldback for short-circuit robustness. Its internal bipolar NPN switch features VCE(SAT) ≤ 680mV at 1.2A and supports boost-capacitor-driven gate drive via BOOST pin for full saturation.
Operation includes programmable UVLO (1.28V threshold), soft-start/tracking via SS pin with 2µA current source, and frequency foldback during startup. The BD pin enables an internal active load (up to 40mA) when SYNC/MODE > 0.8V, eliminating pulse-skipping and maintaining predictable 2MHz ripple above AM band in automotive environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 37V - supports direct regulation from 24V industrial supplies and automotive batteries with 60V transient tolerance. |
| Output Current | 1.2A continuous - sufficient for powering microcontrollers, FPGAs, and interface ICs in compact embedded systems. |
| Switching Frequency | 300kHz to 2.5MHz - adjustable via RT resistor; enables use of sub-10µH inductors and avoids AM-band interference. |
| Feedback Reference | 0.790V to 0.815V (±1.25%) - high-accuracy reference ensures stable output voltage across –40°C to 125°C junction range. |
| Quiescent Current | <1µA in shutdown - critical for battery-powered equipment requiring ultra-low standby power. |
| Minimum On-Time | 100ns - allows 16VIN → 3.3VOUT conversion at 2MHz without duty-cycle limitation. |
| Package Thermal Resistance | JC = 10°C/W, JA = 40°C/W - exposed-pad MSOP enables efficient heat dissipation in high-power-density layouts. |
Pinout & Package
LT3686AIMSE#PBF is housed in a 12-lead plastic MSOP package with exposed thermal pad (Pin 13 = GND). The package measures 3mm × 4.9mm × 1.1mm and requires soldering of the exposed pad to PCB copper for thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1, Exposed Pad Pin 13) | Power and signal ground reference | Primary thermal path; must be soldered to large PCB copper area to maintain JA ≤ 40°C/W. |
| VIN (Pin 2) | Main input supply connection | Supplies internal regulator and power switch; requires local 2.2µF ceramic bypass near pin. |
| BD (Pin 3) | Active load control node | Regulated sink (≤40mA) when SYNC/MODE > 0.8V; maintains fixed frequency and stabilizes boost capacitor recharge. |
| FB (Pin 4) | Feedback voltage sensing input | Regulated to 0.8V reference; sets output via R1/R2 divider; 60–100nA bias current minimizes divider error. |
| SS (Pin 5) | Soft-start and tracking control | 2µA current source ramps external capacitor; tracks both FB voltage and oscillator frequency during startup. |
| RT (Pin 6) | Oscillator frequency programming | Resistor to GND sets frequency from 300kHz–2.5MHz; 15.4kΩ yields 2.1MHz typical. |
| EN/UVLO (Pin 7) | Enable and programmable undervoltage lockout | Pull <0.4V for shutdown; 1.28V threshold enables accurate input monitoring with external resistor divider. |
| SYNC/MODE (Pin 8) | External clock sync input / BD mode select | Accepts ≥200ns pulses up to 2.5MHz; high state (>0.8V) enables BD active load, low state (<0.4V) disables it. |
| BOOST (Pin 9) | Internal switch gate drive supply | Charged via external capacitor and internal diode; must exceed SW voltage by ≥2.2V for full NPN saturation. |
| DA (Pin 10) | Catch diode anode monitor | Detects valley current; triggers frequency foldback if >1.7A to limit inductor current during overload. |
| SW (Pin 11) | Switch node output | Connects to inductor, catch diode cathode, and BOOST capacitor; carries high di/dt switching current. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost diode | Eliminates external Schottky diode in boost path, reducing BOM count and layout area in MSOP footprint. |
| Constant frequency at light loads | BD active load (enabled via SYNC/MODE) prevents pulse-skipping, ensuring predictable EMI profile and low audio-band ripple. |
| Internal compensation | Reduces external component count by eliminating need for compensation network; simplifies design validation. |
| Overvoltage lockout (OVLO) | 37V–39V threshold protects against 60V transients-critical for automotive cold-crank and load-dump survivability. |
| Thermally enhanced MSOP | JC = 10°C/W enables 1.2A operation without heatsink in ambient ≤85°C with minimal PCB copper. |
Applications
| Automotive Infotainment Power | Industrial 24V Distributed Supply |
|---|---|
Use Scenario: Powering DSPs, display controllers, and USB PHYs in head units with 12V/24V battery input and strict EMI limits. IC Role / Device Role / Timing Role: Primary 3.3V/5V buck regulator with fixed 2MHz switching to avoid AM radio band interference. Use Value: BD active load ensures constant frequency under variable load (e.g., display backlight dimming), minimizing conducted emissions. |
Use Scenario: Local regulation of 24V factory bus to 3.3V for PLC I/O modules operating in high-temperature cabinets. IC Role / Device Role / Timing Role: High-input-voltage step-down converter with 37V OVLO and –40°C to 125°C guaranteed operation. Use Value: 100ns minimum on-time supports 24V→3.3V at 2MHz, enabling compact 6.8µH inductor and <1cm² solution size. |
| Battery-Powered Test Equipment | Wall Adapter Secondary Regulation |
Use Scenario: Portable oscilloscope front-end powering ADCs and amplifiers from Li-ion (8.4V–12.6V) with low-noise requirements. IC Role / Device Role / Timing Role: Efficient 5V intermediate rail generator with <1µA shutdown current and soft-start to prevent inrush. Use Value: Internal compensation and integrated boost diode reduce component count, improving reliability in handheld form factor. |
Use Scenario: Regulating unregulated 9V–12V wall adapter output to clean 3.3V for IoT sensor nodes. IC Role / Device Role / Timing Role: Wide-input buck converter accepting variable adapter voltages while maintaining tight output regulation. Use Value: Programmable UVLO (via EN/UVLO divider) rejects brownout conditions below 9V, preventing system reset instability. |
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 | 4V–75V input, 1.5A, no BD pin, requires external bootstrap diode | Lacks BD active load; unsuitable for fixed-frequency light-load EMI control | Select when higher input voltage (>37V) or higher current (>1.2A) is required, and pulse-skipping is acceptable. |
| MP2451DT-LF-Z | 4.5V–36V input, 0.6A, 2MHz fixed frequency, no SYNC or BD functionality | Lower current rating and no light-load frequency control; simpler but less flexible | Choose for cost-sensitive, low-power applications where 0.6A suffices and EMI predictability is secondary. |
Compared with LTC3630EMSE#PBF and MP2451DT-LF-Z, the LT3686AIMSE#PBF uniquely combines 37V max input, 1.2A output, BD-enabled fixed-frequency operation, and SYNC capability in a single MSOP package-making it optimal for automotive and industrial designs demanding EMI control, transient robustness, and layout simplicity.
Availability
LT3686AIMSE#PBF is available at Aetrix Electronics and suitable for automotive infotainment power, industrial 24V distributed supply, and battery-powered test equipment requiring stable component supply and long-term lifecycle support.
Supply support for LT3686AIMSE#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 acquired Linear Technology in 2017 and maintains its high-reliability analog and power management portfolio. Linear's legacy emphasizes precision, ruggedness, and application-specific integration for demanding environments.
The LT3686A product line targets high-input-voltage DC/DC conversion in space-constrained, thermally challenging applications-including automotive, industrial, and instrumentation-where wide VIN range, light-load EMI control, and transient robustness are mandatory.
FAQ
What is the maximum input voltage the LT3686AIMSE#PBF can withstand continuously?
The LT3686AIMSE#PBF supports continuous operation up to 37V input, with overvoltage lockout activating at 37V–39V. Its absolute maximum VIN rating is 60V for nonrepetitive 1-second transients-making it suitable for automotive load-dump conditions. Operation beyond 37V will trigger OVLO shutdown, protecting downstream circuitry.
How does the BD pin function in the LT3686AIMSE#PBF, and what is its design impact?
The BD pin in the LT3686AIMSE#PBF sinks up to 40mA when enabled (SYNC/MODE > 0.8V), acting as an internal active load to prevent pulse-skipping at light loads. This maintains constant 2MHz switching, ensuring predictable output ripple above the audio band and eliminating EMI variability-critical for automotive EMC compliance.
Can the LT3686AIMSE#PBF synchronize to an external clock, and what are the timing requirements?
Yes, the LT3686AIMSE#PBF accepts external synchronization via the SYNC/MODE pin. The input clock must have ≥200ns high/low pulse width, low state <0.4V, high state >0.8V, and frequency higher than the RT-set oscillator (e.g., >2.1MHz for 2.1MHz RT setting). This enables precise EMI alignment in multi-rail systems.
What is the purpose of the DA pin on the LT3686AIMSE#PBF, and how does it affect fault response?
The DA pin monitors catch diode current and triggers valley-current foldback when >1.7A is detected. During output short-circuit, this reduces switching frequency to limit inductor current and prevent thermal runaway-complementing the 1.9A–2.65A peak switch current limit for comprehensive overload protection.
Does the LT3686AIMSE#PBF require an external boost diode, and why or why not?
No, the LT3686AIMSE#PBF integrates a boost diode internally, eliminating the need for an external Schottky diode in the BOOST path. This reduces component count, PCB area, and potential failure points-particularly valuable in the compact 12-lead MSOP package where board space is constrained.
LT3686AIMSE#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
LT3686AIMSE#PBF FAQ
1.How can I place an order for LT3686AIMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3686AIMSE#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 LT3686AIMSE#PBF reliable?
The price and inventory of LT3686AIMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3686AIMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3686AIMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3686AIMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3686AIMSE#PBF?
LT3686AIMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3686AIMSE#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 LT3686AIMSE#PBF?
For technical support, including LT3686AIMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3686AIMSE#PBF requirements.
6.How does Aetrix verify that LT3686AIMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3686AIMSE#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 LT3686AIMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3686AIMSE#PBF?
All LT3686AIMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3686AIMSE#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 LT3686AIMSE#PBF part is unused and in its original packaging.
Return procedure for LT3686AIMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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