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Analog Devices Inc. LT3681EDE#TRPBF
- Part No.:
- LT3681EDE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 14-WFDFN Exposed Pad
- Datasheet:
-
LT3681EDE#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 2A 14DFN
- Quantity:
- Payment:
- Shipping:
Inventory:6,274
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Product details
Overview
LT3681EDE#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 36V, 2A, 2.8MHz current-mode buck switching regulator with integrated power Schottky diode and boost Schottky diode. It features 0.18Ω switch RDS(on), 1.265V feedback reference, and low-ripple Burst Mode operation delivering <15mVP-P output ripple at light loads. It is used in automotive battery regulation and industrial distributed supplies requiring wide input range and compact footprint.
For engineers reviewing the LT3681EDE#TRPBF datasheet, LT3681EDE#TRPBF pinout, LT3681EDE#TRPBF application, or LT3681EDE#TRPBF equivalent, key selection considerations include adjustable 300kHz–2.8MHz switching frequency, integrated Schottky diodes reducing BOM count, Power Good flag signaling 90% VOUT regulation, soft-start via RUN/SS pin, and thermal performance enabled by exposed-pad 14-pin DFN (4mm × 3mm).
Technical Context
The LT3681EDE#TRPBF employs constant-frequency current-mode control with an internal error amplifier driving the VC pin to regulate peak switch current. Its oscillator frequency is set externally via RT-to-ground resistor (8.66kΩ for 2.8MHz), and it includes active clamp on VC for current limiting and RUN/SS ramping for soft-start.
It integrates two Schottky diodes: a 36V/2A power Schottky (DA–DC path) with 0.56V forward drop at 2A, and a boost Schottky (BD–SW path) enabling bipolar NPN switch saturation. Bias current is drawn from VOUT (via BIAS pin) when VOUT > 3V to improve light-load efficiency, and shutdown draws <1µA from VIN.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 34V operating; 36V absolute max - supports 12V/24V automotive and industrial rails with transient tolerance. |
| Output Current | 2A continuous - sufficient for powering FPGAs, microcontrollers, and sensor subsystems without external current boosting. |
| Switching Frequency | 300kHz to 2.8MHz (adjustable via RT) - enables tradeoff between small magnetics (high fSW) and high input voltage ratio support (low fSW). |
| Feedback Reference | 1.265V ±15mV - sets output voltage from 1.265V to 20V using standard resistor divider; tight tolerance simplifies precision regulation. |
| Quiescent Current | 50µA at 12VIN/3.3VOUT in Burst Mode - extends battery life in portable and always-on IoT nodes. |
| Power Good Threshold | VFB + 122mV rising - provides reliable enable signal for downstream logic when output reaches 90% of target. |
| Thermal Package | 14-pin DFN (4mm × 3mm) with exposed thermal pad (Pin 15 = GND, Pin 16 = DC) - θJA = 43°C/W enables 2A operation without forced air in typical PCB layouts. |
Pinout & Package
LT3681EDE#TRPBF is housed in a thermally enhanced 14-pin plastic DFN package (4mm × 3mm) with two exposed pads: Pin 15 (GND) for thermal and signal return, and Pin 16 (DC) as cathode connection for the integrated power Schottky diode.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PG (Pin 1) | Open-collector power good flag | Sinks current when VFB < 90% of regulation; requires external pull-up; valid only if VIN > 3.5V and RUN/SS high. |
| BIAS (Pin 2) | Bias supply input | Accepts ≥3V external source (e.g., VOUT) to power internal regulator - improves efficiency vs. VIN-only biasing. |
| FB (Pin 3) | Feedback sense node | Regulated to 1.265V; connects to resistor divider tap - determines output voltage and enables remote sensing. |
| GND (Pins 4, 7, 15) | Signal and thermal ground | Pins 4/7 are internal signal GND; Pin 15 is exposed thermal pad - must be soldered to large copper pour for thermal management. |
| VC (Pin 5) | Error amplifier output | Controls peak switch current; RC network to GND sets loop compensation - no ESR dependency enables ceramic output caps. |
| RT (Pin 6) | Oscillator frequency set | Resistor to GND programs fSW from 300kHz to 2.8MHz - higher resistance yields lower frequency. |
| DA (Pin 8) | Power Schottky anode | Connects to GND; carries high-frequency catch diode current - requires low-impedance GND path. |
| DC (Pin 9, Pad 16) | Power Schottky cathode | Connects to SW node; shares high-current path with switch - Pad 16 must be routed to SW with minimal inductance. |
| BD (Pin 10) | Boost Schottky anode | Connects to BOOST capacitor anode - supplies charge pump voltage to drive bipolar switch base. |
| BOOST (Pin 11) | Charge pump drive | Capacitor to SW generates >VIN voltage - ensures full saturation of internal NPN switch for low VCE(sat). |
| SW (Pin 12) | Switch node | Drives inductor and BOOST capacitor - high dv/dt node requiring short, low-inductance routing. |
| VIN (Pin 13) | Main input supply | Supplies switch and internal regulator - requires local 4.7µF ceramic bypass close to pin and exposed pad. |
| RUN/SS (Pin 14) | Enable & soft-start control | Logic-high (>2.5V) enables operation; RC ramp from GND implements controlled VOUT rise time. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Power Schottky Diode | 36V/2A rated, 0.56V VF @ 2A - eliminates external catch diode, reduces solution size and thermal stress. |
| Low-Ripple Burst Mode Operation | 50µA IQ @ 12VIN/3.3VOUT, <15mVP-P ripple - maintains high efficiency and low noise during standby or light load. |
| Adjustable Switching Frequency | 300kHz–2.8MHz via single RT resistor - allows optimization for EMI, inductor size, and input/output voltage ratio constraints. |
| Power Good Flag with Hysteresis | 122mV threshold offset + 5mV hysteresis - provides robust system sequencing signal immune to minor VOUT perturbations. |
| Thermally Enhanced DFN Package | 4mm × 3mm footprint with dual exposed pads (GND + DC) - achieves 43°C/W θJA on 2oz copper, supporting full 2A load at 85°C ambient. |
Applications
| Automotive Battery Regulation | Industrial Distributed Supply |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery rail to 3.3V/5V for infotainment MCU and CAN transceivers under cold-crank (4.5V) and load-dump (36V) conditions. IC Role / Device Role / Timing Role: Primary step-down regulator with wide VIN tolerance, integrated Schottky for reliability, and PG flag for safe boot sequencing. Use Value: Eliminates need for external TVS and catch diode; withstands 36V transients without derating; Burst Mode extends battery runtime in sleep mode. | Use Scenario: Providing isolated 5V/12V rails from 24V factory bus to PLC I/O modules, sensors, and fieldbus interfaces in harsh EMI environments. IC Role / Device Role / Timing Role: Compact, high-efficiency DC/DC converter with adjustable fSW to avoid sensitive frequency bands and exposed thermal pad for conduction cooling. Use Value: Reduces board area vs. discrete solutions; 2.8MHz option enables <2.2µH inductors; low EMI due to controlled slew rates and integrated diode. |
| Portable Product Power | Wall Transformer Regulation |
Use Scenario: Converting 9V–24V wall adapter or Li+ battery pack output to 1.8V/3.3V for handheld medical devices with strict battery life targets. IC Role / Device Role / Timing Role: High-efficiency buck regulator leveraging BIAS pin to draw bias from VOUT, minimizing no-load losses. Use Value: Achieves 50µA quiescent current in Burst Mode; integrated diode prevents reverse current during battery switchover; soft-start prevents inrush into capacitive loads. | Use Scenario: Replacing linear regulators in AC/DC adapter secondary-side circuits where 12V–24V DC input must be stepped down to 5V/9V for USB-C PD or legacy peripherals. IC Role / Device Role / Timing Role: Efficient, low-noise switching regulator with low dropout capability and stable operation across variable input voltage. Use Value: Delivers >90% efficiency at full load vs. <40% for linear regulators; integrated Schottky avoids thermal runaway risk; PG flag enables adapter status reporting. |
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 output, 1.2MHz fixed fSW, no integrated Schottky - requires external diode; 10-pin MSOP package. | Lower current rating and no integrated diode limit use in space-constrained 2A designs; better suited for cost-sensitive, lower-power industrial sensors. | Select LTC3631EMSE#PBF only if output current ≤1.5A and PCB area permits external diode placement. |
| MP2451DT-LF-Z | 36V input, 0.6A output, 2MHz fixed fSW, integrated MOSFET but no Schottky - requires external diode; smaller 8-pin SOIC package. | Insufficient current capability for 2A loads; lacks Power Good flag and soft-start control - unsuitable for sequenced systems or battery-powered devices. | MP2451DT-LF-Z is viable only for sub-0.6A auxiliary rails where BOM count reduction is secondary to cost. |
Compared with LTC3631EMSE#PBF and MP2451DT-LF-Z, the LT3681EDE#TRPBF uniquely combines 2A output, integrated 36V Schottky diode, programmable 2.8MHz switching, and Power Good flag in a thermally optimized DFN - making it the only choice for compact, high-reliability 2A buck designs requiring minimal external components and robust fault signaling.
Availability
LT3681EDE#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial distributed supply, and portable product power applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LT3681EDE#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, Inc. (including former Linear Technology products) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving industrial, automotive, communications, and healthcare markets with precision, reliability, and innovation.
The LT3681 product line delivers high-efficiency, wide-input buck regulators with integrated power diodes for space-constrained applications demanding robustness across automotive and industrial temperature ranges (–40°C to 85°C).
FAQ
What is the maximum input voltage rating for LT3681EDE#TRPBF in continuous operation?
The LT3681EDE#TRPBF has an absolute maximum input voltage of 36V. In continuous regulated operation, it safely handles 36V transients. For startup or overload conditions, the maximum sustained input is 34V - exceeding this risks violating minimum off-time constraints and may cause instability or switch overstress. Always verify operating frequency and duty cycle per the datasheet's VIN(MIN)/VIN(MAX) equations when designing for high VIN/VOUT ratios.
Does LT3681EDE#TRPBF require an external catch diode?
No, the LT3681EDE#TRPBF integrates a 36V, 2A power Schottky diode between DA (anode) and DC (cathode) pins, eliminating the need for an external catch diode. This integration reduces solution size, component count, and thermal design complexity. The diode's 0.56V forward voltage at 2A and 100µA leakage at 40V are specified in the Electrical Characteristics table.
How is the switching frequency set on LT3681EDE#TRPBF?
The switching frequency of LT3681EDE#TRPBF is set by connecting a resistor from the RT pin (Pin 6) to ground. Values from 8.66kΩ (2.8MHz) to 187kΩ (300kHz) are supported, with precise values tabulated in the datasheet. The relationship is inverse: lower resistance yields higher frequency. No external capacitor or clock source is required - the oscillator is fully internal and monolithic.
What is the purpose of the BIAS pin on LT3681EDE#TRPBF?
The BIAS pin (Pin 2) on LT3681EDE#TRPBF supplies current to the internal regulator. When connected to a voltage ≥3V (e.g., VOUT), it draws bias power from that source instead of VIN - improving light-load efficiency. This architecture reduces total input current, especially when VIN ≫ VOUT, and is confirmed by the 50µA quiescent current spec at 12VIN/3.3VOUT.
Can LT3681EDE#TRPBF operate in discontinuous conduction mode (DCM)?
Yes, the LT3681EDE#TRPBF can operate in DCM, particularly at light loads or with high inductance values. Its current-mode architecture remains stable in DCM, and Burst Mode operation inherently engages during very light loads. However, maximum output current decreases in DCM, and designers should consult the "Maximum Load Current" graphs in the datasheet and ensure peak inductor current stays below the switch current limit (≥3.5A at low duty cycles).
LT3681EDE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 14-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):
- 34V
- Voltage - Output (Min/Fixed):
- 1.265V
- Voltage - Output (Max):
- 20V
- Current - Output:
- 2A
- Frequency - Switching:
- 300kHz ~ 2.8MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-DFN (4x3)
LT3681EDE#TRPBF FAQ
1.How can I place an order for LT3681EDE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3681EDE#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 LT3681EDE#TRPBF reliable?
The price and inventory of LT3681EDE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3681EDE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3681EDE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3681EDE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3681EDE#TRPBF?
LT3681EDE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3681EDE#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 LT3681EDE#TRPBF?
For technical support, including LT3681EDE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3681EDE#TRPBF requirements.
6.How does Aetrix verify that LT3681EDE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3681EDE#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 LT3681EDE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3681EDE#TRPBF?
All LT3681EDE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3681EDE#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 LT3681EDE#TRPBF part is unused and in its original packaging.
Return procedure for LT3681EDE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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