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Analog Devices Inc. LT3686EDD#TRPBF
- Part No.:
- LT3686EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3686EDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,078
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Product details
Overview
LT3686EDD#TRPBF from Analog Devices (formerly Linear Technology) is a current-mode PWM step-down DC/DC converter with integrated 1.2A bipolar NPN power switch, operating from 3.6V to 37V input and delivering up to 1.2A at adjustable output voltage (e.g., 3.3V or 5V). It features programmable switching frequency (300kHz–2.5MHz), internal compensation, and active load regulation via BD pin for fixed-frequency operation at light loads-enabling compact automotive power supplies.
For engineers reviewing the LT3686EDD#TRPBF datasheet, LT3686EDD#TRPBF pinout, LT3686EDD#TRPBF application, or LT3686EDD#TRPBF equivalent, key selection criteria include its 3.6V–37V wide input range, 100ns minimum on-time, 0.8V feedback reference, overvoltage lockout up to 39V, and 10-lead 3mm × 3mm DFN package with exposed thermal pad.
Technical Context
The LT3686EDD#TRPBF uses current-mode control with cycle-by-cycle peak current limiting and DA-pin-based valley current sensing to manage fault conditions including short-circuit and high-duty-cycle operation. Its oscillator is resistor-programmed (RT pin), supporting frequencies up to 2.5MHz while maintaining stable regulation across –40°C to 125°C junction temperature.
Internal boost circuitry-driven by BOOST and BD pins-generates gate drive voltage >VIN for full saturation of the bipolar NPN switch; soft-start and frequency foldback prevent inrush during startup, and MODE pin enables/disables constant-frequency light-load operation via regulated BD active load (30–40mA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 37V - supports 24V industrial rails and 12V/24V automotive batteries with 55V transient tolerance. |
| Output Current | 1.2A continuous - sufficient for powering microcontrollers, sensors, and interface ICs in embedded systems. |
| Switching Frequency | 300kHz to 2.5MHz - selectable via RT resistor; enables use of sub-10µH inductors and avoids AM-band interference. |
| Feedback Reference | 0.790V to 0.815V (typ. 0.8V) - sets precise output voltage with external resistor divider (e.g., 3.3V = 0.8V × (1 + R1/R2)). |
| Quiescent Current (Shutdown) | <1µA - enables ultra-low-power battery backup and always-on monitoring circuits. |
| Minimum On-Time | 100ns - allows high VIN-to-VOUT conversion ratios (e.g., 16V → 3.3V at 2MHz) without pulse-skipping instability. |
| Overvoltage Lockout | 37V to 39V (typ. 38V) - protects downstream circuitry during load-dump transients in automotive environments. |
Pinout & Package
LT3686EDD#TRPBF is housed in a thermally enhanced 10-lead 3mm × 3mm plastic DFN package with exposed GND pad (Pin 11), requiring soldering to PCB copper for thermal management (θJA = 43°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Main power input | Supplies internal regulator and power switch; must be locally bypassed with ≥2.2µF ceramic capacitor. |
| BD (Pin 2) | Boost diode return | Tied to VOUT to enable internal Schottky boost diode; regulates active load (30–40mA) when MODE > 0.8V. |
| FB (Pin 3) | Feedback sense | Regulated to 0.8V reference; sets output voltage via resistor divider (R1/R2); bias current ≤100nA. |
| SS (Pin 4) | Soft-start/track control | Charged by internal 2µA current source; ramps FB and frequency simultaneously; resets during faults. |
| RT (Pin 5) | Oscillator programming | Resistor to GND sets frequency (e.g., 15.4kΩ = 2.1MHz); supports 300kHz–2.5MHz range. |
| EN/UVLO (Pin 6) | Enable/undervoltage lockout | 1.27V threshold enables UVLO function; <0.4V forces shutdown (IQ < 1µA). |
| MODE (Pin 7) | Light-load mode select | >0.8V enables fixed-frequency operation via BD active load; <0.4V disables it for pulse-skipping efficiency. |
| BOOST (Pin 8) | Gate drive boost supply | Provides voltage >VIN to fully saturate bipolar NPN switch; requires ≥0.22µF ceramic capacitor to SW. |
| DA (Pin 9) | Catch diode anode sense | Monitors catch diode current; triggers frequency foldback if valley current exceeds 1.7A (fault protection). |
| SW (Pin 10) | Switch node | Connects to inductor, catch diode cathode, and BOOST capacitor; carries high di/dt switching current. |
| GND (Pin 11, Exposed Pad) | Power ground | Only ground connection; must be soldered to large PCB copper area for thermal and EMI performance. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated bipolar NPN power switch | 1.2A rating with 680mV VCE(SAT) at full load enables high-efficiency, low-component-count buck conversion. |
| Programmable switching frequency | 300kHz–2.5MHz via single RT resistor supports layout optimization and EMI mitigation across diverse input/output combinations. |
| Constant-frequency light-load operation | BD pin active load (30–40mA) maintains full switching frequency when MODE > 0.8V, eliminating audio-band ripple and enabling predictable filtering. |
| Robust fault protection | Cycle-by-cycle peak current limit (1.85–2.65A), DA-pin valley current foldback, OVLO (38V), and thermal shutdown ensure reliability in automotive transients. |
| Internal compensation & boost diode | Reduces external component count by eliminating external compensation network and discrete boost diode. |
Applications
| Automotive Infotainment Power Supply | Industrial Sensor Node Regulator |
|---|---|
Use Scenario: Powers 3.3V MCU, CAN transceiver, and display driver from 12V/24V vehicle battery with load-dump immunity. IC Role / Device Role / Timing Role: Primary step-down regulator with 37V OVLO, 100ns min-on-time, and AM-band–free 2.1MHz operation. Use Value: Eliminates need for pre-regulator stage; maintains stable 3.3V output during cold-crank (4.5V) and load-dump (38V) events. | Use Scenario: Supplies 5V to isolated RS-485 transceivers and analog front-end in factory automation PLC modules. IC Role / Device Role / Timing Role: Wide-input buck converter with internal compensation and 1.2A capability for distributed 5V rail generation. Use Value: Reduces BOM count vs. controller+MOSFET solutions; operates continuously from 3.6V–37V without external UVLO circuitry. |
| Portable Medical Device Power | Smart Building Controller Supply |
Use Scenario: Delivers 3.3V to low-power ARM Cortex-M microcontroller and BLE radio in battery-backed handheld diagnostic tool. IC Role / Device Role / Timing Role: High-efficiency buck regulator with <1µA shutdown current and soft-start for clean power-up sequencing. Use Value: Extends battery life in standby; prevents inrush into capacitive loads during wake-up from deep sleep. | Use Scenario: Generates 5V for PoE-powered HVAC controllers interfacing with 24V AC building management systems. IC Role / Device Role / Timing Role: Input-tolerant buck converter accepting rectified 24V AC (up to ~34V DC) with robust thermal design. Use Value: Operates reliably across wide input range without derating; exposed pad ensures thermal stability in enclosed enclosures. |
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#TRPBF | 40V max input, 1.5A output, 3mm × 4mm MSOP; no BD pin or active load; higher IQ (12µA) | Lacks fixed-frequency light-load mode; better suited for cost-sensitive non-audio applications | Select when board space allows larger package and audio-band ripple is acceptable |
| TPS54340DDAR | 42V max input, 3.5A output, SO-8; external compensation; no integrated boost diode; 115ns min-on-time | Higher current, but requires external MOSFET gate driver and compensation components | Select when >1.2A output or SO-8 footprint compatibility is required |
Compared with LTC3630EMSE#TRPBF and TPS54340DDAR, LT3686EDD#TRPBF uniquely combines 37V input, 1.2A output, 100ns min-on-time, and BD-enabled constant-frequency light-load operation in a 3mm × 3mm DFN-making it optimal for space-constrained automotive and industrial converters where predictable ripple and transient immunity are critical.
Availability
LT3686EDD#TRPBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial sensor nodes, and portable medical devices requiring stable component supply with guaranteed long-term availability.
Supply support for LT3686EDD#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) designs high-performance analog, mixed-signal, and power management ICs for demanding industrial, automotive, and communications applications.
The LT3686EDD#TRPBF belongs to Linear's high-voltage monolithic buck regulator product line, engineered specifically for robust, compact power conversion in automotive and industrial environments with wide input ranges and stringent transient immunity requirements.
FAQ
What is the maximum input voltage the LT3686EDD#TRPBF can withstand during transients?
The LT3686EDD#TRPBF has an absolute maximum VIN rating of 55V and includes overvoltage lockout (OVLO) that activates at 37V–39V (typ. 38V). This protects the device during automotive load-dump events while allowing normal operation up to 37V DC. Transient spikes beyond 39V but below 55V are tolerated briefly, though sustained operation above 37V is not recommended. The LT3686EDD#TRPBF integrates this protection without external components.
How does the BD pin function in the LT3686EDD#TRPBF, and what happens if it's left unconnected?
The BD pin on the LT3686EDD#TRPBF connects to the internal boost Schottky diode cathode and must be tied to VOUT to enable proper boost capacitor charging. If left unconnected or floating, the boost circuit fails, causing insufficient gate drive voltage and potential switch saturation loss or thermal shutdown. When MODE > 0.8V, the LT3686EDD#TRPBF regulates ~30–40mA through BD to maintain fixed-frequency operation at light loads.
Can the LT3686EDD#TRPBF operate at 2.5MHz, and what design considerations apply?
Yes, the LT3686EDD#TRPBF supports up to 2.5MHz via RT = 9.53kΩ. At this frequency, minimum inductor value increases (e.g., ~2.2µH for 3.3V output), PCB layout must minimize parasitic inductance, and efficiency drops ~3–5% due to edge losses. The LT3686EDD#TRPBF's 100ns minimum on-time remains sufficient for 16V→3.3V conversion at 2.5MHz, avoiding pulse-skipping instability.
What is the purpose of the DA pin on the LT3686EDD#TRPBF, and how does it affect fault response?
The DA pin on the LT3686EDD#TRPBF senses catch diode anode current to detect valley current during discontinuous conduction mode. When DA current exceeds 1.7A, the LT3686EDD#TRPBF reduces switching frequency to limit inductor valley current-preventing runaway during output short-circuit or high-VIN fault conditions. This complements the primary peak current limit (1.85–2.65A) for comprehensive overcurrent protection.
Is the LT3686EDD#TRPBF RoHS-compliant and lead-free, and what is its temperature grade?
Yes, the LT3686EDD#TRPBF is RoHS-compliant and features lead-free finish (Pb-free). Its "E" grade specifies operation from –40°C to +125°C junction temperature, validated per Linear Technology/Analog Devices qualification standards. The part marking "LDYC" on the 10-lead DFN package confirms this temperature range and lead-free compliance per manufacturer documentation.
LT3686EDD#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)
LT3686EDD#TRPBF FAQ
1.How can I place an order for LT3686EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3686EDD#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 LT3686EDD#TRPBF reliable?
The price and inventory of LT3686EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3686EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3686EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3686EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3686EDD#TRPBF?
LT3686EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3686EDD#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 LT3686EDD#TRPBF?
For technical support, including LT3686EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3686EDD#TRPBF requirements.
6.How does Aetrix verify that LT3686EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3686EDD#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 LT3686EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3686EDD#TRPBF?
All LT3686EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3686EDD#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 LT3686EDD#TRPBF part is unused and in its original packaging.
Return procedure for LT3686EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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