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Analog Devices Inc. LT3684EMSE#PBF
- Part No.:
- LT3684EMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3684EMSE#PBF.pdf
- Description:
- IC REG BUCK ADJ 2A 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,312
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Product details
Overview
LT3684EMSE#PBF from Analog Devices (formerly Linear Technology) is a monolithic 300 kHz–2.8 MHz current-mode step-down switching regulator with integrated 0.18 Ω NPN switch and boost Schottky diode, supporting 3.6 V–34 V input and delivering up to 2 A at adjustable output voltages from 1.265 V to 20 V. It features power good flag, soft-start via RUN/SS pin, and operates in thermally enhanced 10-lead MSOP package with exposed GND pad - used in automotive battery regulation and industrial distributed supplies.
For engineers reviewing the LT3684EMSE#PBF datasheet, LT3684EMSE#PBF pinout, LT3684EMSE#PBF application, or LT3684EMSE#PBF equivalent, key selection considerations include its 2.8 MHz max switching frequency enabling compact 4.7 µH inductors, 1.265 V feedback reference for precise output setting, <1 µA shutdown current, integrated boost diode eliminating external component, and thermal performance validated for –40°C to +85°C operation.
Technical Context
The LT3684EMSE#PBF implements constant-frequency current-mode control using an internal RS flip-flop driven by a resistor-programmable oscillator (RT pin), with peak current sensing between VIN and SW pins. Its error amplifier regulates FB to 1.265 V and drives VC to modulate switch conduction time, while VC clamping enables active current limiting and soft-start synchronization with RUN/SS ramp.
Power delivery architecture includes dual supply paths: bias current drawn from VIN by default, or from higher-efficiency BIAS pin (≥3 V, typically VOUT); BOOST pin drives the internal NPN switch via external capacitor/diode charge pump, ensuring full saturation even at high duty cycles. Frequency foldback below 90% FB voltage improves overload robustness during startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6 V to 34 V operating; 36 V absolute maximum - supports wide-range industrial and automotive inputs including 24 V bus transients. |
| Output Current | Up to 2 A continuous - sufficient for powering FPGA I/O banks, microcontroller cores, or sensor signal chains. |
| Switching Frequency | Adjustable 300 kHz to 2.8 MHz via RT resistor - enables tradeoff between small 3 mm × 3 mm solution size and efficiency at light loads. |
| Feedback Reference | 1.265 V ±15 mV - allows accurate output programming from 1.265 V to 20 V using standard 1% resistors. |
| Shutdown Current | <1 µA - enables ultra-low-power system sleep modes without auxiliary LDOs. |
| Power Good Flag | Open-collector PG asserts when VOUT reaches 90% of target - provides reliable sequencing signal for downstream logic or processors. |
| Thermal Package | 10-lead MSOP with exposed pad (θJA = 45°C/W) - delivers 125°C max junction temperature with minimal PCB copper area. |
Pinout & Package
LT3684EMSE#PBF is housed in a 10-lead plastic MSOP package with exposed thermal pad (Pin 11) that must be soldered to PCB ground for optimal thermal performance. Pin numbering follows standard MSOP top-view layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (Pin 1) | Boost Diode Anode Connection | Connects to anode of external Schottky diode forming charge pump for BOOST pin drive voltage. |
| BOOST (Pin 2) | Charge Pump Output | Provides >VIN voltage to fully saturate internal NPN switch; rated to 56 V max, 30 V above SW. |
| SW (Pin 3) | Switch Node | Drives external inductor and catch diode; carries high di/dt pulsed current - requires tight layout and low-inductance path. |
| VIN (Pin 4) | Main Input Supply | Supplies internal regulator and switch; must be locally bypassed with ≥4.7 µF X7R ceramic capacitor. |
| RUN/SS (Pin 5) | Enable & Soft-Start Control | Logic-high (>2.5 V) enables operation; RC network here sets controlled VOUT ramp rate during startup. |
| PG (Pin 6) | Power Good Output | Open-collector flag pulled high externally; goes low when FB drops below 90% of 1.265 V reference. |
| BIAS (Pin 7) | Efficiency-Optimized Bias Supply | Accepts ≥3 V external source (e.g., VOUT) to reduce quiescent loss - improves efficiency at high VIN/VOUT ratios. |
| FB (Pin 8) | Feedback Input | Regulated to 1.265 V; connects to resistor divider tap - determines output voltage with ±15 mV tolerance over temperature. |
| VC (Pin 9) | Error Amplifier Output | Controls peak switch current; compensation network (RC + CC) connected here stabilizes current-mode loop. |
| RT (Pin 10) | Frequency Programming | Resistor to GND sets switching frequency from 300 kHz (187 kΩ) to 2.8 MHz (8.66 kΩ). |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Boost Schottky Diode | Eliminates external diode, reducing BOM count and board area while maintaining efficient NPN switch saturation across full duty cycle range. |
| Current-Mode Control Architecture | Enables fast transient response and inherent cycle-by-cycle current limiting - simplifies compensation and improves stability with ceramic output capacitors. |
| Programmable Switching Frequency | 300 kHz–2.8 MHz adjustment via single RT resistor - balances EMI, efficiency, and passive component size for space-constrained designs. |
| Thermally Enhanced MSOP Package | 10-lead MSOP with exposed GND pad achieves θJA = 45°C/W - supports 2 A load without heatsink in ambient ≤85°C environments. |
| Power Good Flag with Hysteresis | PG output includes 10 mV hysteresis and validates only when VIN > 3.5 V and RUN/SS is high - prevents false assertions during brown-out or enable sequencing. |
Applications
| Automotive Battery Regulation | Industrial Distributed Supply Regulation |
|---|---|
Use Scenario: Regulating 12 V or 24 V vehicle battery to 3.3 V or 5 V for infotainment ECUs and ADAS sensors under cold-crank (4.5 V) and load-dump (36 V) conditions. IC Role / Device Role / Timing Role: Primary buck converter providing stable, sequenced power with PG flag for MCU reset coordination and fault reporting. Use Value: 34 V operating input and 36 V transient tolerance meet ISO 7637-2 pulse 5a requirements; <1 µA shutdown current extends battery life in parked mode. |
Use Scenario: Point-of-load conversion in programmable logic controllers (PLCs) and industrial I/O modules where 24 V field bus powers multiple isolated 5 V/3.3 V rails. IC Role / Device Role / Timing Role: High-efficiency, thermally robust DC-DC stage delivering 2 A to FPGA configuration circuitry or analog front-end ADCs. Use Value: BIAS pin operation reduces power dissipation by >30% vs. VIN-biased mode at 24 V input; exposed pad ensures reliable operation at 85°C ambient. |
| Portable Product Power | Wall Transformer Regulation |
Use Scenario: Powering handheld test equipment or portable medical monitors from wide-input wall adapters (9–32 V) with variable load profiles. IC Role / Device Role / Timing Role: Main system regulator managing dynamic load steps from display backlight to wireless transceiver bursts. Use Value: 2.8 MHz operation allows use of 4.7 µH inductor and 22 µF ceramic output cap - achieving <10 mVpp ripple in <150 mm² footprint. |
Use Scenario: Replacing linear regulators in legacy AC/DC adapter designs to improve efficiency and reduce thermal derating at 40°C ambient. IC Role / Device Role / Timing Role: Compact, drop-in buck replacement for 78xx-style regulators in space-limited consumer electronics enclosures. Use Value: Integrated switch and boost diode eliminate 3 external components; soft-start prevents inrush into large output caps typical in adapter outputs. |
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 | 40 V input, 1.5 A output, 1.25 V reference, no integrated boost diode - requires external Schottky. | Better suited for higher input voltage margin (e.g., 36 V sustained) but lower current capability and added BOM complexity. | Select when input exceeds 34 V continuously and external diode layout is acceptable. |
| MP2451DT-LF-Z | 36 V input, 0.6 A output, 0.8 V reference, no PG flag or BIAS pin - simpler feature set, lower cost. | Targeted at cost-sensitive, lower-current applications like IoT sensor nodes where sequencing and efficiency optimization are secondary. | Select when 2 A output is unnecessary and bill-of-materials cost is prioritized over thermal performance or power sequencing. |
Compared with LTC3630EMSE#PBF and MP2451DT-LF-Z, the LT3684EMSE#PBF uniquely combines 2 A output, integrated boost diode, PG flag, and BIAS pin efficiency enhancement - making it optimal for thermally constrained, medium-power industrial and automotive point-of-load designs requiring reliability and feature completeness.
Availability
LT3684EMSE#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial distributed supply regulation, and portable product power applications requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3684EMSE#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 high-performance power management portfolio with rigorous qualification and long-term product support.
The LT3684EMSE#PBF belongs to Linear's monolithic buck regulator family designed for rugged, high-efficiency DC-DC conversion in automotive, industrial, and communications infrastructure where input transients, thermal constraints, and feature integration are critical.
FAQ
What is the maximum input voltage rating for LT3684EMSE#PBF during normal regulation versus transient conditions?
The LT3684EMSE#PBF has an absolute maximum VIN rating of 36 V. During normal regulation with no startup or short-circuit events, input transients up to 36 V are acceptable regardless of switching frequency. However, during startup or short-circuit conditions, the maximum safe operating input voltage is limited to 34 V - verified per Absolute Maximum Ratings and confirmed in the datasheet's Applications Information section on input voltage range.
Does LT3684EMSE#PBF require an external boost diode, and what is its function?
No, the LT3684EMSE#PBF integrates a boost Schottky diode internally - connected to the BD pin - which forms part of the charge pump driving the BOOST pin. This eliminates the need for an external diode and ensures the internal NPN switch remains fully saturated across all duty cycles, improving efficiency and simplifying layout. The BD pin must still be connected to the anode of the external boost capacitor's Schottky diode as shown in the functional block diagram.
How does the BIAS pin improve efficiency in LT3684EMSE#PBF, and what voltage must be applied?
The BIAS pin on the LT3684EMSE#PBF accepts an external voltage ≥3 V (typically the regulated output VOUT) to power the internal control circuitry instead of drawing bias current from VIN. This reduces total input current and improves efficiency - especially when VIN is significantly higher than VOUT (e.g., 24 V → 3.3 V). The minimum valid BIAS voltage is 2.7 V, with guaranteed operation at 3.0 V per Electrical Characteristics table.
What is the purpose of the VC pin on LT3684EMSE#PBF, and how is it used in compensation?
VC is the output of the internal transconductance error amplifier in the LT3684EMSE#PBF. It directly controls peak switch current and serves as the primary loop compensation node. A series RC network (RC + CC) is connected from VC to GND to provide phase boost and stabilize the current-mode control loop. The datasheet specifies typical values and design equations, and Figure 2 in the Applications Information section shows the exact equivalent circuit used for compensation analysis.
Can LT3684EMSE#PBF operate in discontinuous conduction mode (DCM), and how does it affect maximum output current?
Yes, the LT3684EMSE#PBF can operate in discontinuous conduction mode (DCM) at light loads or with high switching frequencies and small inductors. In DCM, maximum output current decreases because peak inductor current approaches the switch current limit more rapidly. The datasheet confirms this behavior in Typical Performance Characteristics (Figure G04–G05) and states that IOUT(MAX) = ILIM – ΔIL/2, where ILIM drops from 3.5 A (low duty) to 2.5 A (duty = 0.8), and ΔIL increases with higher VIN or smaller L.
LT3684EMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) 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 ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LT3684EMSE#PBF FAQ
1.How can I place an order for LT3684EMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3684EMSE#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 LT3684EMSE#PBF reliable?
The price and inventory of LT3684EMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3684EMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3684EMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3684EMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3684EMSE#PBF?
LT3684EMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3684EMSE#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 LT3684EMSE#PBF?
For technical support, including LT3684EMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3684EMSE#PBF requirements.
6.How does Aetrix verify that LT3684EMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3684EMSE#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 LT3684EMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3684EMSE#PBF?
All LT3684EMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3684EMSE#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 LT3684EMSE#PBF part is unused and in its original packaging.
Return procedure for LT3684EMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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