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Analog Devices Inc. LT3686AIDD#PBF
- Part No.:
- LT3686AIDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3686AIDD#PBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,974
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Product details
Overview
LT3686AIDD#PBF 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 or adjustable output with internal power switch, 2.5MHz max switching frequency, and integrated boost diode. Designed for automotive battery and industrial 24V supply regulation, it supports fixed-frequency operation down to light loads via BD pin active load control.
For engineers reviewing the LT3686AIDD#PBF datasheet, LT3686AIDD#PBF pinout, LT3686AIDD#PBF application, or LT3686AIDD#PBF equivalent, key selection criteria include its 100ns minimum on-time enabling high VIN-to-VOUT ratios at 2MHz, cycle-by-cycle current limit with DA-pin valley sensing, and SYNC/MODE dual-function interface for external clock synchronization and light-load mode control.
Technical Context
The LT3686AIDD#PBF employs current-mode PWM control with internal bipolar NPN power switch and integrated boost diode, enabling efficient operation up to 37V input. Its oscillator is programmable from 300kHz to 2.5MHz via RT resistor, and features frequency foldback during start-up to limit inrush current.
It implements dual protection architecture: peak switch current limit (typ. 2.3A) combined with DA-pin valley current limit (1.7A), plus overvoltage lockout (38V typ.) and precision UVLO (3.6V threshold). The BD pin enables constant-frequency operation at light loads by regulating an internal active 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 direct connection to automotive batteries and industrial 24V rails without pre-regulation. |
| Output Current | 1.2A continuous - sufficient for powering microcontrollers, sensors, and interface ICs in space-constrained systems. |
| Switching Frequency | 300kHz to 2.5MHz, adjustable via RT pin - enables use of sub-10µH inductors and avoids AM band interference. |
| Feedback Reference | 0.795V to 0.815V (typ. 0.8V) - ensures ±1.5% output voltage accuracy across temperature and line/load conditions. |
| Quiescent Current | <1µA in shutdown (VEN/UVLO < 0.4V) - critical for battery-powered equipment requiring ultra-low standby power. |
| Minimum On-Time | 100ns (typ.) - allows 16V input to 3.3V output conversion at 2MHz without pulse-skipping in continuous conduction mode. |
| Thermal Performance | θJA = 43°C/W (DFN package) - requires exposed pad soldered to PCB ground plane for reliable 1.2A operation at 125°C junction temperature. |
Pinout & Package
LT3686AIDD#PBF is housed in a 10-lead plastic DFN package (3mm × 3mm, 0.75mm height) with exposed thermal pad (Pin 11) that must be soldered to PCB ground for thermal management. Pin pitch is 0.5mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pins 1,2) | Power input | Supplies internal regulator and power switch; requires local 2.2µF ceramic bypass capacitor. |
| BD (Pin 3) | Active load control | Regulated current sink (up to 40mA) activated when SYNC/MODE > 0.8V to maintain fixed frequency at light loads. |
| FB (Pin 4) | Feedback sense | Regulated to 0.8V reference; sets output voltage via resistor divider (R1/R2); R2 ≤ 20kΩ recommended. |
| SS (Pin 5) | Soft-start/Tracking | Internal 2µA current source charges external capacitor; ramps FB and frequency simultaneously during startup. |
| RT (Pin 6) | Oscillator programming | Resistor to ground sets switching frequency (300kHz–2.5MHz); 15.4kΩ yields 2.1MHz typical. |
| EN/UVLO (Pin 7) | Enable / UVLO input | 1.28V threshold enables precise undervoltage lockout; pulled below 0.4V shuts down device (IQ < 1µA). |
| SYNC/MODE (Pin 8) | Clock sync / mode select | Accepts external clock (≥200ns pulse width); >0.8V enables BD active load; <0.4V disables it. |
| BOOST (Pin 9) | Switch drive boost | Charged via internal diode and external capacitor to ~VIN + 2.4V; drives bipolar NPN switch fully saturated. |
| DA (Pin 10) | Catch diode anode sense | Monitors catch diode current; triggers frequency foldback if valley current exceeds 1.7A during fault conditions. |
| 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) | Power and thermal ground | Only ground connection; must be soldered to large PCB copper area to achieve θJA = 43°C/W. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost diode | Eliminates external Schottky diode in most designs, reducing BOM count and board area while maintaining efficiency. |
| Constant frequency at light loads | BD pin active load maintains full switching frequency (e.g., 2MHz) down to mA-level loads, ensuring predictable EMI and low audio-band ripple. |
| External synchronization | SYNC/MODE pin accepts external clock up to 2.5MHz, enabling deterministic timing alignment in multi-rail power systems. |
| Robust fault protection | Dual current limiting (switch peak + DA valley), thermal shutdown, OVLO (38V), and UVLO (3.6V) ensure survivability in harsh environments. |
| Internal compensation | Reduces external component count by eliminating need for loop compensation network - simplifies layout and validation. |
Applications
| Automotive Infotainment Power | Industrial Sensor Node Supply |
|---|---|
|
Use Scenario: Regulating 12V/24V vehicle battery to 3.3V for MCU, CAN transceiver, and display controller in head unit. IC Role / Device Role / Timing Role: Primary buck converter providing stable, low-noise 3.3V rail with AM-band avoidance and transient robustness. Use Value: 2.5MHz operation enables compact 6.8µH inductor and 22µF ceramic output cap; OVLO protects against load-dump transients up to 60V. |
Use Scenario: Powering wireless sensor nodes (BLE/Zigbee) from 24V industrial bus with strict size and efficiency requirements. IC Role / Device Role / Timing Role: High-efficiency step-down regulator delivering 1.2A peak current with ultra-low shutdown IQ (<1µA) for battery backup. Use Value: BD-enabled fixed-frequency light-load operation ensures consistent EMI profile during sleep/wake cycles; SS pin enables controlled power-up sequencing. |
| Medical Point-of-Care Device | Ruggedized Edge Computing Module |
|
Use Scenario: Generating isolated 5V/3.3V rails from wide-input wall adapter (9–36V) in portable diagnostic equipment. IC Role / Device Role / Timing Role: Main DC/DC converter with precision UVLO (3.6V) and thermal shutdown for safe operation in unventilated enclosures. Use Value: 100ns min-on-time supports 36V-to-5V conversion at 2MHz; internal compensation accelerates design validation under IEC 60601 safety constraints. |
Use Scenario: Powering FPGA I/O banks and DDR memory interfaces in fanless edge gateway operating from 24V PoE++ or DIN rail supply. IC Role / Device Role / Timing Role: High-current buck stage with cycle-by-cycle current limiting and DA-pin fault detection for short-circuit resilience. Use Value: 1.2A output with 2.3A switch limit handles FPGA dynamic current spikes; exposed DFN pad enables conduction cooling in sealed metal housings. |
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 range; 1.5A output; no BD pin or active load; MSOP-12 only | Lacks light-load fixed-frequency capability; better suited for higher-current, non-automotive applications where pulse-skipping is acceptable | Select LTC3630EMSE#PBF when higher output current (1.5A) is required and BD-controlled light-load performance is not needed. |
| MP2451DT-LF-Z | 3.3V–36V input; 0.6A output; 2MHz fixed frequency; no SYNC, no BD, no OVLO protection | Lower current rating and missing automotive-grade protections (OVLO, precise UVLO, thermal derating) | Choose MP2451DT-LF-Z only for cost-sensitive, non-safety-critical 0.6A applications where full LT3686AIDD#PBF feature set is unnecessary. |
Compared with LTC3630EMSE#PBF and MP2451DT-LF-Z, the LT3686AIDD#PBF uniquely combines 1.2A output, BD-enabled fixed-frequency light-load operation, 60V transient tolerance, and 2.5MHz programmability - making it optimal for space-constrained automotive and industrial systems demanding predictable EMI and robust fault handling.
Availability
LT3686AIDD#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial sensor nodes, and medical point-of-care devices requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for LT3686AIDD#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 industrial, automotive, communications, and healthcare markets.
The LT3686A series belongs to Linear Technology's high-voltage monolithic buck regulator product line, designed specifically for robust, compact power conversion in automotive and industrial environments with wide input ranges and stringent reliability requirements.
FAQ
What is the maximum input voltage the LT3686AIDD#PBF can handle continuously?
The LT3686AIDD#PBF operates continuously from 3.6V to 37V input. Its absolute maximum rating is 60V for non-repetitive 1-second transients, and 55V for continuous operation. Overvoltage lockout activates at 38V typical to protect downstream circuitry, making it suitable for automotive load-dump scenarios when properly decoupled.
How does the BD pin function in the LT3686AIDD#PBF?
The BD pin on the LT3686AIDD#PBF provides an internally regulated active load (up to 40mA) when the SYNC/MODE pin is held above 0.8V. This maintains constant switching frequency at light loads, eliminating pulse-skipping and associated audio-band noise - a key advantage for automotive and noise-sensitive applications.
Can the LT3686AIDD#PBF synchronize to an external clock, and what are the requirements?
Yes, the LT3686AIDD#PBF supports 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-programmed oscillator frequency (max 2.5MHz). Synchronization enables deterministic timing in multi-rail systems.
What is the purpose of the DA pin on the LT3686AIDD#PBF?
The DA pin on the LT3686AIDD#PBF senses catch diode anode current and triggers frequency foldback when valley current exceeds 1.7A. This works with the switch peak current limit (2.3A typ.) to provide dual-level overcurrent protection during output short-circuit events, especially at high input voltages.
Does the LT3686AIDD#PBF require external compensation components?
No, the LT3686AIDD#PBF features internal compensation, eliminating the need for external Type II or Type III compensation networks. This reduces component count, simplifies PCB layout, and accelerates design validation - particularly valuable in high-reliability applications where loop stability must be guaranteed across temperature and manufacturing variance.
LT3686AIDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN 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:
- 10-DFN (3x3)
LT3686AIDD#PBF FAQ
1.How can I place an order for LT3686AIDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3686AIDD#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 LT3686AIDD#PBF reliable?
The price and inventory of LT3686AIDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3686AIDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3686AIDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3686AIDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3686AIDD#PBF?
LT3686AIDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3686AIDD#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 LT3686AIDD#PBF?
For technical support, including LT3686AIDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3686AIDD#PBF requirements.
6.How does Aetrix verify that LT3686AIDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3686AIDD#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 LT3686AIDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3686AIDD#PBF?
All LT3686AIDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3686AIDD#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 LT3686AIDD#PBF part is unused and in its original packaging.
Return procedure for LT3686AIDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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