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Analog Devices Inc. LT3686AIDD#TRPBF
- Part No.:
- LT3686AIDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3686AIDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,392
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Product details
Overview
LT3686AIDD#TRPBF from Analog Devices (formerly Linear Technology) is a 3.6V–37V input, 1.2A synchronous step-down DC/DC converter in a thermally enhanced 10-lead 3mm × 3mm DFN package. It delivers regulated 3.3V output with internal power switch, 2MHz switching frequency, adjustable frequency (300kHz–2.5MHz), and constant-frequency operation at light loads via BD-pin active load control. It is used in automotive battery regulation and industrial 24V supply conversion.
For engineers reviewing the LT3686AIDD#TRPBF datasheet, LT3686AIDD#TRPBF pinout, LT3686AIDD#TRPBF application, or LT3686AIDD#TRPBF equivalent, key selection criteria include its 100ns minimum on-time for high VIN-to-VOUT ratios, ±1% FB reference accuracy, overvoltage lockout up to 39V, thermal shutdown protection, and external synchronization capability - all critical for noise-sensitive automotive and industrial power designs.
Technical Context
The LT3686AIDD#TRPBF employs current-mode PWM control with internal slope compensation and cycle-by-cycle current limiting. Its bipolar NPN power switch is driven by an internal boost circuit referenced to the BOOST pin, enabling efficient saturation across wide input ranges.
It integrates soft-start with tracking, programmable UVLO (1.28V threshold), frequency foldback during startup, and dual-mode SYNC/MODE pin functionality - enabling both external clock synchronization and BD-pin active load activation to maintain fixed-frequency operation down to zero load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 37V continuous; withstands 60V transients - supports direct connection to 24V industrial rails and 12V/24V automotive batteries with transient robustness. |
| Output Current | 1.2A continuous - sufficient for powering microcontrollers, sensors, and interface ICs in compact embedded systems. |
| Switching Frequency | Adjustable 300kHz to 2.5MHz via RT resistor - enables optimization of size (high-freq) vs. efficiency (low-freq) and AM-band avoidance (≥1.8MHz). |
| Feedback Reference | 0.790V to 0.815V (±1.25%) - ensures precise output voltage regulation across temperature and line/load conditions. |
| Minimum On-Time | 100ns typical - allows 16VIN → 3.3VOUT conversion at 2MHz without pulse-skipping in continuous conduction mode. |
| Quiescent Current (Shutdown) | <1µA - enables ultra-low-power standby in battery-backed systems requiring long shelf life. |
| Overvoltage Lockout | 37V to 39V threshold - protects downstream circuitry during load-dump events in automotive environments. |
Pinout & Package
LT3686AIDD#TRPBF is housed in a 10-lead, 3mm × 3mm plastic DFN package with exposed thermal pad (Pin 11 = GND). The package features 43°C/W junction-to-ambient thermal resistance and requires soldering of the exposed pad to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pins 1,2) | Power input supply | Supplies internal regulator and power switch; must be locally bypassed with ≥2.2µF X7R ceramic capacitor. |
| BD (Pin 3) | Active load control terminal | When enabled via SYNC/MODE >0.8V, sinks up to 40mA to maintain fixed-frequency operation at light loads and assist boost capacitor recharge. |
| FB (Pin 4) | Feedback node | Regulated to 0.8V reference; sets output voltage via resistor divider (e.g., R2=10kΩ, R1=(VOUT/0.8−1)×R2). |
| SS (Pin 5) | Soft-start and tracking input | Charged by internal 2µA current source; ramps FB and frequency simultaneously to limit inrush current and prevent startup overshoot. |
| RT (Pin 6) | Oscillator programming | Resistor to GND sets switching frequency (e.g., 15.4kΩ → 2.1MHz); tolerance directly impacts frequency accuracy. |
| EN/UVLO (Pin 7) | Enable and undervoltage lockout | Pull <0.4V to shut down (IQ<1µA); 1.28V threshold enables programmable UVLO using external resistor divider. |
| SYNC/MODE (Pin 8) | Sync clock input / mode select | Accepts external clock ≥200ns pulse width; also selects BD active load enable (>0.8V) or disable (<0.4V). |
| BOOST (Pin 9) | Switch driver supply | Charged via internal diode and external capacitor; provides ~VIN+2.4V to fully 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 waveform. |
| GND (Pin 11 Exposed Pad) | Primary ground reference | Only ground connection; must be soldered to large PCB copper area for thermal management and low-noise operation. |
Key Features
| Feature | Design Value |
|---|---|
| Internal boost diode and compensation | Eliminates need for external boost diode and reduces loop compensation components - simplifies BOM and layout. |
| Constant-frequency light-load operation | BD-pin active load maintains full switching frequency down to zero load - avoids audible noise and ensures predictable EMI profile. |
| External synchronization capability | SYNC/MODE pin accepts external clock up to 2.5MHz - enables coherent multi-rail timing and eliminates beat frequencies in dense power systems. |
| Robust fault protection | Includes cycle-by-cycle current limit (1.85–2.65A), thermal shutdown, overvoltage lockout (39V), and DA-pin valley-current foldback - survives short-circuit and overvoltage events. |
| Low minimum on-time (100ns) | Enables high-step-down ratios (e.g., 16V→3.3V) at 2MHz without entering pulse-skipping mode - preserves regulation and ripple performance. |
Applications
| Automotive Infotainment Power Supply | Industrial PLC I/O Module |
|---|---|
|
Use Scenario: Regulating 12V/24V vehicle battery to stable 3.3V for MCU, CAN transceiver, and display controller. IC Role / Device Role / Timing Role: Primary step-down regulator with AM-band-avoiding 2MHz switching and load-dump transient protection. Use Value: Maintains fixed-frequency operation under light-load idle states, eliminating audio-band ripple and ensuring EMC compliance in cabin electronics. |
Use Scenario: Converting 24V distributed rail to 3.3V for isolated digital I/O logic and sensor signal conditioning. IC Role / Device Role / Timing Role: High-input-voltage buck converter with programmable UVLO and thermal derating for unattended factory-floor operation. Use Value: Withstands 37V overvoltage events and delivers 1.2A continuously at 85°C ambient - supports long-life industrial deployment without derating. |
| Portable Test Equipment | Smart Building Sensor Node |
|
Use Scenario: Powering FPGA-based measurement subsystems from wall adapter (9–36V) with minimal board space. IC Role / Device Role / Timing Role: Compact, high-frequency DC/DC with integrated compensation and soft-start for clean power sequencing. Use Value: 3mm × 3mm DFN + internal boost diode reduces solution footprint by >30% versus discrete alternatives - critical for handheld form factors. |
Use Scenario: Battery-backed wireless sensor node requiring ultra-low quiescent current and reliable cold-start from depleted Li-ion. IC Role / Device Role / Timing Role: Efficient step-down regulator with <1µA shutdown current and precision 1.28V UVLO for battery voltage monitoring. Use Value: Enables >10-year shelf life in storage and reliable wake-up from 3.6V battery minimum - extends field maintenance intervals. |
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 4V–42V input range; 1.5A output; no BD-pin active load; MSOP-12 only | Lacks constant-frequency light-load mode - unsuitable where EMI predictability or audio-noise avoidance is required | Choose when higher output current is needed and light-load frequency stability is not critical. |
| MP2451DT-LF-Z | 3.3V–36V input; 0.6A output; no synchronization; no active load; smaller 8-pin SOIC | Half the output current and no SYNC/MODE or BD functionality - limited to low-power non-automotive use | Choose only for cost-sensitive, low-current applications where feature set can be reduced. |
Compared with LTC3630EMSE#PBF and MP2451DT-LF-Z, the LT3686AIDD#TRPBF uniquely combines 1.2A output, 2MHz capability, BD-pin active load, and synchronization in a 3mm × 3mm DFN - making it the only option meeting stringent automotive EMI and thermal requirements in space-constrained designs.
Availability
LT3686AIDD#TRPBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC modules, and portable test equipment requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3686AIDD#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LT3686AIDD#TRPBF belongs to Linear's high-voltage monolithic buck regulator product line, designed specifically for robust, compact power conversion in harsh environments including automotive battery systems and industrial 24V infrastructure.
FAQ
What is the maximum input voltage the LT3686AIDD#TRPBF can safely handle?
The LT3686AIDD#TRPBF has an absolute maximum input voltage rating of 60V for nonrepetitive 1-second transients, and 55V for continuous operation. Its overvoltage lockout activates at 37V–39V, protecting downstream circuitry during automotive load-dump events. For sustained operation, the recommended maximum is 37V per the datasheet's operating specification - exceeding this risks triggering OVLO shutdown or damaging internal structures.
Does the LT3686AIDD#TRPBF require an external catch diode?
Yes, the LT3686AIDD#TRPBF requires an external Schottky catch diode connected between SW and GND (anode to DA pin). The MBRM140 (1A, 40V) is explicitly recommended in the datasheet. Unlike synchronous buck converters, the LT3686AIDD#TRPBF uses a bipolar NPN switch and relies on this external diode for freewheeling current path and valley-current sensing via the DA pin.
How does the BD pin function in the LT3686AIDD#TRPBF?
The BD pin on the LT3686AIDD#TRPBF enables an internal active load that sinks up to 40mA when activated by the SYNC/MODE pin (>0.8V). This maintains constant switching frequency at light or no load - preventing pulse-skipping, minimizing output ripple above the audio band, and ensuring predictable EMI. It also aids boost capacitor recharge during high-duty-cycle operation.
Can the LT3686AIDD#TRPBF be synchronized to an external clock?
Yes, the LT3686AIDD#TRPBF supports external synchronization via its SYNC/MODE pin. It accepts square-wave clocks up to 2.5MHz with ≥200ns high/low pulse widths and logic thresholds of 0.4V (low) and 0.8V (high). The external clock must exceed the RT-programmed frequency; for example, a 2.1MHz RT setting requires sync input >2.1MHz per Table 1 in the datasheet.
What package type and thermal characteristics does the LT3686AIDD#TRPBF have?
The LT3686AIDD#TRPBF uses a 10-lead, 3mm × 3mm plastic DFN package with exposed thermal pad (Pin 11 = GND). Its junction-to-ambient thermal resistance is 43°C/W, and the exposed pad must be soldered to a large PCB ground plane for effective heat dissipation. This package supports operation from –40°C to 125°C ambient, matching automotive and industrial temperature requirements.
LT3686AIDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN 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:
- 10-DFN (3x3)
LT3686AIDD#TRPBF FAQ
1.How can I place an order for LT3686AIDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3686AIDD#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 LT3686AIDD#TRPBF reliable?
The price and inventory of LT3686AIDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3686AIDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3686AIDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3686AIDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3686AIDD#TRPBF?
LT3686AIDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3686AIDD#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 LT3686AIDD#TRPBF?
For technical support, including LT3686AIDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3686AIDD#TRPBF requirements.
6.How does Aetrix verify that LT3686AIDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3686AIDD#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 LT3686AIDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3686AIDD#TRPBF?
All LT3686AIDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3686AIDD#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 LT3686AIDD#TRPBF part is unused and in its original packaging.
Return procedure for LT3686AIDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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