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Analog Devices Inc. LT3684IDD#PBF
- Part No.:
- LT3684IDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3684IDD#PBF.pdf
- Description:
- IC REG BUCK ADJ 2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:386
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Product details
Overview
LT3684IDD#PBF from Analog Devices (formerly Linear Technology) is a 36V, 2A, adjustable-frequency (300kHz–2.8MHz) monolithic buck switching regulator with integrated 0.18Ω NPN switch and boost Schottky diode. It operates from 3.6V to 34V input, delivers 1.265V–20V adjustable output, and features power good flag, soft-start, and current-mode control for fast transient response - used in industrial power supplies and automotive battery regulation.
For engineers reviewing the LT3684IDD#PBF datasheet, LT3684IDD#PBF pinout, LT3684IDD#PBF application, or LT3684IDD#PBF equivalent, this page provides verified package mapping (10-pin 3mm × 3mm DFN), thermal performance data (θJC = 10°C/W), shutdown current (<1µA), feedback reference (1.265V), and confirmed alternative options for wide-input DC/DC conversion designs.
Technical Context
The LT3684IDD#PBF implements constant-frequency current-mode control using an internal transconductance error amplifier, RS flip-flop oscillator, and peak-current sensing across the VIN–SW path. Its VC pin directly controls switch peak current via voltage-to-current gain of 3.5A/V and includes active clamp limiting.
Operation relies on external RT resistor programming (300kHz–2.8MHz), BOOST capacitor-assisted gate drive for bipolar switch saturation, and BIAS pin sourcing from VOUT to improve efficiency at high VIN/VOUT ratios. Frequency foldback activates during startup or overload to limit output current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 34V operating; 36V absolute max - supports 24V industrial rails and automotive cold-crank transients. |
| Output Current | 2A continuous - sufficient for FPGA core supplies or multi-rail embedded systems without derating at 125°C. |
| Switching Frequency | 300kHz to 2.8MHz (RT-programmable) - enables compact 4.7µH inductors and ceramic output capacitors. |
| Feedback Reference | 1.265V ±15mV - sets output accuracy and enables precise 3.3V/5V/12V regulation with standard resistor dividers. |
| Shutdown Current | <1µA - ensures ultra-low system standby power in battery-backed instrumentation. |
| Power Good Flag | Open-collector PG asserts when VOUT reaches 90% of target - provides reliable sequencing signal for downstream logic. |
| Thermal Resistance | θJC = 10°C/W - requires exposed pad soldering to PCB ground plane for full 2A operation at 125°C junction. |
Pinout & Package
LT3684IDD#PBF uses a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed pad (Pin 11) tied to GND. The package supports high-power density layouts and achieves θJA = 45°C/W with 2-in² 2-oz copper.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (Pin 1) | Boost diode anode connection | Connects external Schottky anode to enable BOOST voltage generation above VIN for switch saturation. |
| BOOST (Pin 2) | Boost capacitor drive node | Provides >VIN gate drive to internal NPN switch; rated to 56V with 30V max above SW pin. |
| SW (Pin 3) | Switch node | High-current output of internal NPN transistor; connects to inductor, catch diode, and BOOST capacitor. |
| VIN (Pin 4) | Main input supply | Supplies internal regulator and switch; must be locally bypassed with ≥4.7µF X7R ceramic capacitor. |
| RUN/SS (Pin 5) | Enable & soft-start control | Logic-level enable (≥2.5V = ON); RC network here generates controlled VOUT ramp during startup. |
| PG (Pin 6) | Power good open-collector output | Sinks current when VOUT < 90% of regulation; requires external pull-up for system sequencing. |
| BIAS (Pin 7) | Efficiency-optimized bias supply | Tie to VOUT (≥3V) to reduce quiescent loss; draws current from lowest available >3V rail. |
| FB (Pin 8) | Feedback reference input | Regulated to 1.265V; connects to resistor divider tap for output voltage programming. |
| VC (Pin 9) | Error amplifier output | Controls peak switch current; RC compensation network here stabilizes current-mode loop. |
| RT (Pin 10) | Oscillator frequency set | Resistor to GND programs switching frequency from 300kHz to 2.8MHz per datasheet table. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost Schottky diode | Eliminates external diode, reducing BOM count and PCB area while maintaining >90% efficiency at 2A. |
| Current-mode topology | Enables single-pole loop compensation, stable operation with ceramic output capacitors, and <10µs load transient recovery. |
| Adjustable soft-start | RC network on RUN/SS pin prevents inrush current and output overshoot during power-up sequences. |
| Thermally enhanced DFN | Exposed pad (Pin 11) soldered to PCB ground delivers 10°C/W junction-to-case resistance for full 2A rating at 125°C. |
| Wide temperature grade | Rated for –40°C to +125°C operation - qualified for under-hood automotive and industrial control environments. |
Applications
| Automotive Battery Regulation | Industrial Distributed Power |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery to 3.3V/5V for infotainment ECUs and ADAS sensors. IC Role / Device Role / Timing Role: Primary step-down regulator handling cold-crank (4.5V) to load-dump (36V) transients with power good signaling. Use Value: Integrated boost diode and 34V operating range eliminate external protection components; PG flag enables safe microcontroller boot sequencing. |
Use Scenario: Local point-of-load conversion in PLC backplanes and motor drive I/O modules. IC Role / Device Role / Timing Role: High-efficiency 2A buck converter powering isolated communication interfaces (RS-485, CAN) and analog front-ends. Use Value: BIAS pin operation from VOUT reduces heat dissipation at 24V input; 125°C rating ensures reliability in sealed enclosures. |
| Portable Product Power | Wall Transformer Supply |
Use Scenario: Converting 5V–24V USB-C PD or wall adapter outputs to 1.8V/3.3V for portable medical devices. IC Role / Device Role / Timing Role: Compact, low-noise DC/DC stage replacing linear regulators to extend battery life. Use Value: 2.8MHz max switching frequency allows use of 1.0µH inductors and 10µF ceramic caps - total solution size < 100mm². |
Use Scenario: Replacing aging 78xx linear regulators in legacy AC/DC adapters for IoT gateways and smart home hubs. IC Role / Device Role / Timing Role: Efficient 2A buck stage accepting wide-input unregulated DC from bridge rectifiers. Use Value: 3.6V min input enables operation down to brownout conditions; soft-start prevents transformer inrush stress. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#PBF | 40V input, 1.5A, 3mm × 4mm MSOP; no integrated boost diode; requires external Schottky. | Better suited for space-constrained designs needing higher VIN rating but lower current. | Select when input exceeds 34V or MSOP footprint preferred; add external diode and adjust layout for BOOST node. |
| MP2451DT-LF-Z | 36V input, 0.6A, 8-pin SOIC; no PG flag or BIAS pin; fixed 2.2MHz frequency. | Targeted at cost-sensitive, low-current consumer applications without sequencing requirements. | Choose only for sub-1A loads where PG, soft-start, and efficiency optimization are non-critical. |
Compared with LTC3631EMSE#PBF and MP2451DT-LF-Z, the LT3684IDD#PBF uniquely combines 2A capability, integrated boost diode, power good signaling, and BIAS pin efficiency enhancement - making it optimal for industrial and automotive 2A buck applications requiring robustness and feature completeness.
Availability
LT3684IDD#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial distributed power, and portable product power applications requiring stable component supply across extended temperature ranges.
Supply support for LT3684IDD#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 precision power management portfolio with rigorous automotive and industrial qualification standards.
The LT3684IDD#PBF belongs to Linear's high-voltage monolithic buck regulator family, designed specifically for rugged 24V/36V system power conversion where integration, thermal performance, and transient robustness are critical.
FAQ
What is the maximum input voltage rating for LT3684IDD#PBF in continuous operation?
The LT3684IDD#PBF has an absolute maximum VIN rating of 36V, but continuous operation is limited to 34V. Transient inputs up to 36V are acceptable only when the output is in regulation and no startup or short-circuit events occur. This distinction is critical for automotive load-dump survival design - the LT3684IDD#PBF must be used with appropriate input filtering if exposed to 36V transients.
Does LT3684IDD#PBF require an external catch diode?
No, the LT3684IDD#PBF integrates a boost Schottky diode and does not require an external catch diode. The BD pin connects to the anode of the internal diode, and the BOOST pin provides the necessary gate-drive voltage above VIN to saturate the internal NPN switch. External diodes are unnecessary and would degrade efficiency and increase board area.
How is the switching frequency set on LT3684IDD#PBF?
The switching frequency of LT3684IDD#PBF is set by connecting a resistor from the RT pin (Pin 10) to ground. Values from 8.66kΩ (2.8MHz) to 187kΩ (300kHz) are specified in the datasheet. For example, a 60.4kΩ resistor yields 800kHz operation. The RT resistor must be placed close to the RT pin with short traces to minimize noise coupling into the oscillator.
What is the purpose of the BIAS pin on LT3684IDD#PBF?
The BIAS pin on LT3684IDD#PBF allows the IC to draw bias current from the regulated output voltage (typically VOUT) instead of VIN, significantly improving efficiency when VIN is much higher than VOUT - such as in 24V-to-3.3V conversion. When BIAS is connected to ≥3V, quiescent current drops from ~2mA to ~0.85mA, reducing thermal load and enabling higher ambient temperature operation.
Can LT3684IDD#PBF operate in dropout mode?
No, the LT3684IDD#PBF is a nonsynchronous buck regulator and cannot operate in dropout (100% duty cycle). Its minimum off-time is 150ns, limiting maximum duty cycle to ~95% at 2.8MHz. For applications requiring true dropout, a low-dropout linear regulator or synchronous buck controller with external MOSFETs must be used instead of the LT3684IDD#PBF.
LT3684IDD#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):
- 34V
- Voltage - Output (Min/Fixed):
- 1.265V
- Voltage - Output (Max):
- 20V
- Current - Output:
- 2A
- Frequency - Switching:
- 300kHz ~ 3MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3684IDD#PBF FAQ
1.How can I place an order for LT3684IDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3684IDD#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 LT3684IDD#PBF reliable?
The price and inventory of LT3684IDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3684IDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3684IDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3684IDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3684IDD#PBF?
LT3684IDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3684IDD#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 LT3684IDD#PBF?
For technical support, including LT3684IDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3684IDD#PBF requirements.
6.How does Aetrix verify that LT3684IDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3684IDD#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 LT3684IDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3684IDD#PBF?
All LT3684IDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3684IDD#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 LT3684IDD#PBF part is unused and in its original packaging.
Return procedure for LT3684IDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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