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Analog Devices Inc. LT3686AIMSE#TRPBF
- Part No.:
- LT3686AIMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 12-TSSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3686AIMSE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 12MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,118
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Product details
Overview
LT3686AIMSE#TRPBF from Analog Devices (formerly Linear Technology) is a 3.6V to 37V input, 1.2A synchronous step-down DC/DC converter in thermally enhanced 12-lead MSOP package. It delivers regulated 3.3V or adjustable output with internal 1.2A bipolar NPN switch, 0.8V feedback reference, and programmable 300kHz–2.5MHz switching frequency. Designed for automotive battery and industrial 24V supply regulation, it features cycle-by-cycle current limit, thermal shutdown, and BD-pin active load for fixed-frequency operation at light loads.
For engineers reviewing the LT3686AIMSE#TRPBF datasheet, LT3686AIMSE#TRPBF pinout, LT3686AIMSE#TRPBF application, or LT3686AIMSE#TRPBF equivalent, key selection criteria include its 100ns minimum on-time enabling high VIN-to-VOUT ratios (e.g., 16V→3.3V @ 2MHz), ±1% FB reference accuracy over temperature, integrated boost diode, and SYNC/MODE pin dual functionality for external clock synchronization and BD active load enable/disable.
Technical Context
The LT3686AIMSE#TRPBF employs peak current-mode control with internal slope compensation and a 0.8V precision bandgap reference. Its oscillator is resistor-programmable via RT pin (300kHz–2.5MHz) and supports external synchronization above the programmed frequency. The BD pin enables an internal regulated active load when SYNC/MODE > 0.8V, eliminating pulse-skipping and maintaining constant 2MHz (or user-set) frequency down to zero load.
Protection architecture includes cycle-by-cycle switch current limiting (typ. 2.3A), thermal shutdown, overvoltage lockout (37V–39V trip), and precision undervoltage lockout (3.4V–3.6V). Soft-start is implemented via SS pin with 2µA internal current source; tracking mode allows coordinated startup with other rails. Internal compensation eliminates external compensation components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 37V continuous; withstands 60V transients - supports direct connection to automotive batteries and 24V industrial rails. |
| Output Current | 1.2A continuous - sufficient for powering microcontrollers, sensors, and interface ICs in compact systems. |
| Feedback Reference | 0.790V to 0.815V (±1.25%) - ensures tight output regulation across temperature and line/load conditions. |
| Switching Frequency | 300kHz to 2.5MHz, RT-programmable - enables use of small 6.8µH inductors and avoids AM-band interference. |
| Minimum On-Time | 100ns - allows 16V input to 3.3V output conversion at 2MHz without pulse-skipping. |
| Quiescent Current | <1µA in shutdown (VEN/UVLO < 0.4V) - critical for battery-powered equipment with long sleep cycles. |
| Package | 12-Lead MSOP with exposed pad - JA = 40°C/W; requires soldered GND pad for thermal performance and EMI reduction. |
Pinout & Package
LT3686AIMSE#TRPBF uses a 12-lead plastic MSOP package with exposed thermal pad (Pin 13 = GND). The exposed pad must be soldered to a large PCB copper area for thermal management and low-impedance grounding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pin 1, Exposed Pad Pin 13) | Power and signal ground reference | Only ground connection; exposed pad is primary thermal path and must be soldered to PCB plane. |
| VIN (Pin 2) | Main power input | Supplies internal regulator and switch; requires local 2.2µF ceramic bypass near pin. |
| BD (Pin 3) | Active load control node | Regulated current sink (≤40mA) enabled when SYNC/MODE > 0.8V; maintains full switching frequency at light loads. |
| FB (Pin 4) | Output voltage sense input | Regulated to 0.8V reference; sets VOUT via R1/R2 divider; 60–100nA bias current affects high-R divider accuracy. |
| SS (Pin 5) | Soft-start and tracking control | 2µA current source charges external capacitor; ramps FB reference and frequency simultaneously until 0.8V is reached. |
| RT (Pin 6) | Oscillator frequency programming | Resistor to GND sets frequency (300kHz–2.5MHz); tolerance directly impacts switching frequency accuracy. |
| EN/UVLO (Pin 7) | Enable and programmable UVLO | 1.28V threshold enables UVLO function; external resistor divider sets turn-on voltage; <0.4V forces shutdown (<1µA IQ). |
| SYNC/MODE (Pin 8) | External sync input / BD mode select | Accepts external clock ≥200ns pulse width; high state (>0.8V) enables BD active load; low state (<0.4V) disables it. |
| BOOST (Pin 9) | Switch driver supply | Charged via internal diode + external capacitor; provides ~VIN+2.4V to fully saturate bipolar NPN switch. |
| DA (Pin 10) | Catch diode anode monitor | Detects 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; high dv/dt node requiring tight layout. |
| - (Pin 12) | No connect | Not internally connected; left floating or tied to GND per layout best practices. |
Key Features
| Feature | Design Value |
|---|---|
| Internal Boost Diode | Eliminates need for external bootstrap diode; reduces BOM count and layout complexity in high-side drive path. |
| Constant Frequency at Light Loads | BD active load (enabled via SYNC/MODE) prevents pulse-skipping, ensuring predictable EMI profile and low audio-band ripple. |
| Programmable UVLO with Hysteresis | EN/UVLO pin supports resistor-divider programming of turn-on voltage (e.g., 12V system) with built-in 2.4µA hysteresis current. |
| Overvoltage Lockout Protection | Shuts down at 37V–39V input - safeguards downstream circuitry during load dump transients in automotive environments. |
| Thermally Enhanced MSOP | JA = 40°C/W with exposed pad soldered - enables 1.2A operation at 125°C ambient without derating in typical PCB layouts. |
Applications
| Automotive Infotainment Power Supply | Industrial Sensor Node Regulator |
|---|---|
Use Scenario: Powers DSP, display controller, and CAN transceiver in head unit using 12V battery rail with load dump immunity. IC Role / Device Role / Timing Role: Primary 3.3V/1.2A buck regulator with fixed 2MHz operation and BD-enabled light-load stability. Use Value: Eliminates audible noise from pulse-skipping and meets CISPR-25 Class 5 EMI limits due to consistent switching frequency above AM band. | Use Scenario: Converts 24V factory bus to 5V/3.3V for wireless sensor modules operating in harsh temperature environments. IC Role / Device Role / Timing Role: High-input-voltage step-down regulator with –40°C to 125°C guaranteed operation and 37V OVLO protection. Use Value: Sustains regulation during brownouts and surges common in industrial plants; no external compensation reduces design cycle time. |
| Portable Medical Device Power | Test Equipment Auxiliary Rail |
Use Scenario: Supplies FPGA core and ADC in handheld ultrasound device powered by Li-ion battery (8.4V–12.6V). IC Role / Device Role / Timing Role: Efficient 3.3V buck converter with <1µA shutdown IQ and soft-start for controlled power-up sequencing. Use Value: Extends battery life during standby; SS pin enables tracking with main 5V rail to prevent back-powering of analog sections. | Use Scenario: Generates clean 5V auxiliary supply for DUT interface circuitry in automated test equipment with 24V backplane. IC Role / Device Role / Timing Role: Compact, low-noise buck regulator synchronized to system clock via SYNC/MODE pin. Use Value: Reduces beat frequencies and EMI coupling into sensitive measurement paths through deterministic switching alignment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIMSE#TRPBF | 42V input, 2.5A, Silent Switcher architecture; 2.2MHz fixed freq; lower IQ (2.5µA) but no BD pin or active load. | Lacks BD-enabled fixed-frequency light-load operation; superior EMI performance but higher cost and larger solution size. | Select when ultra-low EMI is mandatory and pulse-skipping is acceptable at light loads. |
| TPS54202DDCR | 28V input, 2A, 500kHz–2.5MHz sync-capable; FET-based; no internal boost diode; requires external bootstrap diode. | Higher max current but lacks OVLO >37V and guaranteed –40°C to 125°C operation; needs external compensation. | Select for cost-sensitive industrial designs where 28V max input suffices and layout space allows external components. |
Compared with LT8609SIMSE#TRPBF and TPS54202DDCR, the LT3686AIMSE#TRPBF uniquely combines 37V OVLO, BD-pin light-load frequency control, internal boost diode, and guaranteed automotive-grade temperature range in a compact MSOP - making it optimal for space-constrained, transient-heavy 24V/automotive systems requiring predictable light-load behavior.
Availability
LT3686AIMSE#TRPBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial sensor nodes, and portable medical devices requiring stable component supply, long-term lifecycle support, and guaranteed –40°C to 125°C operation.
Supply support for LT3686AIMSE#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed by the acquisition of Linear Technology in 2017.
The LT3686A belongs to ADI's high-voltage monolithic buck regulator product line, designed specifically for robust power conversion in automotive, industrial, and avionics applications where wide input range, transient immunity, and thermal reliability are critical.
FAQ
What is the maximum input voltage rating for LT3686AIMSE#TRPBF, and how does it handle transients?
The LT3686AIMSE#TRPBF has a continuous input voltage rating of 3.6V to 37V, with absolute maximum ratings of 60V for nonrepetitive 1-second transients on VIN and EN/UVLO pins. Its overvoltage lockout (OVLO) circuit trips between 37V and 39V to protect internal circuitry. During load dump events common in automotive systems, the part shuts down safely and resumes operation once input falls below OVLO hysteresis - ensuring reliable operation in 12V/24V battery environments without external TVS clamping in many cases. This behavior is confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables of the official LT3686A datasheet.
How does the BD pin function in LT3686AIMSE#TRPBF, and what design impact does it have?
The BD pin in LT3686AIMSE#TRPBF enables an internal regulated active load that draws up to 40mA when the SYNC/MODE pin is held above 0.8V. This maintains constant switching frequency (e.g., 2MHz) even at zero load, eliminating pulse-skipping and associated audio-band output ripple. It also assists boost capacitor recharge during high-duty-cycle operation. Designers must ensure BD voltage stays below 6V for activation and route SYNC/MODE appropriately - tying it to GND disables the feature. This capability is unique to the LT3686A family and is documented in the Pin Functions and Applications Information sections of the datasheet.
Can LT3686AIMSE#TRPBF synchronize to an external clock, and what are the timing requirements?
Yes, LT3686AIMSE#TRPBF supports external synchronization via the SYNC/MODE pin, which accepts square-wave inputs with minimum 200ns high and low pulse widths, logic-high >0.8V, and logic-low <0.4V. The external clock frequency must exceed the RT-programmed oscillator frequency (e.g., 2.5MHz sync signal for a 2MHz RT setting). Synchronization aligns switching edges to reduce beat frequencies and EMI in multi-rail systems. This capability is explicitly stated in the Features list and Operation section of the LT3686A datasheet and differentiates it from the non-synchronizable LT3686 variant.
What is the purpose of the DA pin in LT3686AIMSE#TRPBF, and how does it affect fault response?
The DA (Diode Anode) pin in LT3686AIMSE#TRPBF monitors valley current in the external catch diode. When DA current exceeds 1.7A, the part initiates frequency foldback to limit inductor current and prevent damage during output short-circuit or overload conditions. This works in tandem with the 2.3A peak switch current limit to provide robust fault protection. The DA comparator ensures safe operation even with high input voltages and low-inductance designs - a key safety feature detailed in the Block Diagram and Operation sections of the LT3686A datasheet.
Does LT3686AIMSE#TRPBF require external compensation components, and why?
No, LT3686AIMSE#TRPBF does not require external compensation components. It features fully internal compensation optimized for stability with standard output capacitor ESR and capacitance ranges. This is confirmed in the Features list ("Internally Compensated") and Applications Information section, which states "Internal compensation reduces external component count." Designers only need to select appropriate output capacitance (e.g., 22µF X7R ceramic for 3.3V@2MHz) and follow layout guidelines - significantly simplifying design validation and reducing bill-of-materials cost compared to externally compensated regulators.
LT3686AIMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 12-TSSOP (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):
- 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#TRPBF FAQ
1.How can I place an order for LT3686AIMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3686AIMSE#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 LT3686AIMSE#TRPBF reliable?
The price and inventory of LT3686AIMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3686AIMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3686AIMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3686AIMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3686AIMSE#TRPBF?
LT3686AIMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3686AIMSE#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 LT3686AIMSE#TRPBF?
For technical support, including LT3686AIMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3686AIMSE#TRPBF requirements.
6.How does Aetrix verify that LT3686AIMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3686AIMSE#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 LT3686AIMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3686AIMSE#TRPBF?
All LT3686AIMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3686AIMSE#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 LT3686AIMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3686AIMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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