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Analog Devices Inc. LT3685EDD#TRPBF
- Part No.:
- LT3685EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3685EDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,055
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Product details
Overview
LT3685EDD#TRPBF from Analog Devices is a 36V, 2A, 2.4MHz monolithic step-down switching regulator with integrated 0.25Ω bipolar NPN switch, boost Schottky diode, and overvoltage lockout (36V min, 38V typ) enabling safe 60V transient tolerance. It delivers regulated 3.3V/5V outputs in automotive battery regulation and industrial supplies.
For engineers reviewing the LT3685EDD#TRPBF datasheet, LT3685EDD#TRPBF pinout, LT3685EDD#TRPBF application, or LT3685EDD#TRPBF equivalent, key selection factors include its 200kHz–2.4MHz adjustable frequency, 0.790V feedback reference, power good flag, soft-start via RUN/SS, and thermal performance in the 3mm × 3mm DFN package with exposed GND pad.
Technical Context
The LT3685EDD#TRPBF uses constant-frequency current-mode control with an external RT resistor to set switching frequency from 200kHz to 2.4MHz. Its internal error amplifier drives the VC pin to regulate peak switch current, while the BOOST/SW/BD pins enable high-efficiency saturation of the integrated bipolar switch using an external bootstrap network.
Overvoltage protection disables switching when VIN exceeds 36V (min), allowing safe 60V non-repetitive transients. The power good (PG) flag asserts when FB reaches 89% of 0.790V, and shutdown draws <1µA via RUN/SS pin pulled low.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.6V to 36V continuous; withstands 60V transients via OVP shutdown |
| Max Output Current | 2A DC load with proper thermal design and inductor selection |
| Switching Frequency | Adjustable 200kHz–2.4MHz via RT resistor; enables compact magnetics |
| Feedback Reference | 0.790V ±10mV; sets output voltage via resistor divider on FB pin |
| Quiescent Current | <1µA in shutdown (RUN/SS = 0V); 450µA typical operating IQ |
| Power Good Threshold | Asserts when VOUT ≥ 89% of programmed value; open-collector PG output |
| Switch On-Resistance | 0.25Ω typical; enables high efficiency at 2A with low conduction loss |
Pinout & Package
LT3685EDD#TRPBF is housed in a thermally enhanced 10-pin (3mm × 3mm) plastic DFN package with exposed GND pad (Pin 11), requiring PCB soldering for optimal thermal performance (θJA = 45°C/W, θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RT (Pin 10) | Oscillator frequency programming | Resistor to GND sets switching frequency from 200kHz to 2.4MHz |
| VC (Pin 9) | Error amplifier output | Controls peak switch current; RC network to GND provides loop compensation |
| FB (Pin 8) | Voltage feedback input | Regulated to 0.790V; connects to resistor divider for output voltage setting |
| PG (Pin 7) | Power good flag | Open-collector output active low until VOUT reaches 89% of target |
| SYNC (Pin 6) | External clock input | Accepts 250kHz–2MHz sync signal; ground if unused |
| BD (Pin 1) | Boost diode anode supply | Connects to external Schottky anode; powers internal bias regulator when >3V |
| BOOST (Pin 2) | Bootstrap drive voltage | Provides >VIN voltage to fully saturate internal bipolar switch |
| SW (Pin 3) | Switch node | Connects to inductor, catch diode cathode, and boost capacitor |
| VIN (Pin 4) | Main input supply | Supplies internal regulator and switch; requires local 4.7µF ceramic bypass |
| RUN/SS (Pin 5) | Enable & soft-start control | <0.2V = shutdown (<1µA IQ); ramped voltage enables controlled VOUT rise |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost Schottky diode | Eliminates external diode; reduces BOM count and board area in buck topology |
| Saturating bipolar NPN switch | 0.25Ω RCE(SAT) enables high efficiency at 2A without MOSFET gate drive complexity |
| 60V transient survivability | OVP circuit disables switching above 36V (min), protecting downstream circuitry during load dump |
| Adjustable soft-start | R-C network on RUN/SS pin controls output voltage ramp rate, limiting inrush current |
| Thermally enhanced DFN | 3mm × 3mm footprint with exposed GND pad supports 2A operation at 125°C ambient |
Applications
| Automotive Battery Regulation | Industrial Power Supplies |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery rails to 3.3V/5V for infotainment ECUs and ADAS sensors under load-dump conditions. IC Role / Device Role / Timing Role: Primary step-down regulator with OVP-enabled 60V transient tolerance and power good signaling for system sequencing. Use Value: Eliminates need for external TVS or discrete OVP circuitry while maintaining 2A output under cold-crank (3.6V) and load-dump (60V) extremes. | Use Scenario: Distributed 5V/12V regulation in PLC I/O modules and motor drive control boards with wide-input industrial SMPS. IC Role / Device Role / Timing Role: High-voltage buck converter supporting 36V max input and synchronized operation across multiple rails. Use Value: Adjustable 200kHz–2.4MHz frequency allows EMI optimization and use of small 4.7µH inductors, reducing solution size by >30% vs. 500kHz alternatives. |
| Set-Top Box Power | Wall Adapter Replacement |
Use Scenario: Replacing linear regulators in cable/satellite STB mainboard power with efficient 3.3V/5V generation from 12V intermediate rail. IC Role / Device Role / Timing Role: Compact, high-frequency buck converter delivering low-noise, well-regulated outputs with soft-start for hot-plug compatibility. Use Value: 0.790V reference and tight FB tolerance (±10mV) ensure ±1.5% output accuracy across line/load/temperature, meeting STB standby power requirements. | Use Scenario: Integrated primary-side regulation in universal-input wall adapters replacing flyback controllers for 5V/2A USB-C PD accessory power. IC Role / Device Role / Timing Role: Secondary-side synchronous buck controller accepting up to 36V DC input from rectified AC-DC stage. Use Value: Integrated boost diode and 0.25Ω switch reduce component count and improve full-load efficiency to >92% at 12VIN/5VOUT, lowering thermal stress in enclosed adapters. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIV#TRPBF | 42V input, 2.5A, 2MHz, integrated MOSFETs; no boost diode; lower IQ (2.5µA) | Requires external bootstrap cap; better suited for ultra-low-IQ portable apps | Choose LT8609S for higher input voltage margin (42V) and lower quiescent current; avoid if BD pin functionality or bipolar switch robustness is required. |
| MP2451DT-LF-Z | 36V input, 2A, 2.2MHz, external diode; 0.18Ω MOSFET RDS(on); no PG or SYNC | Lacks power good flag and synchronization; simpler compensation but no OVP clamping | Choose MP2451 for cost-sensitive designs where PG flag and 60V transient survival are not mandatory. |
Compared with LT8609SIV#TRPBF and MP2451DT-LF-Z, the LT3685EDD#TRPBF uniquely combines integrated boost diode, bipolar switch saturation for high-current reliability, and guaranteed 60V transient tolerance - making it preferred for automotive and industrial environments demanding robustness over minimal IQ or MOSFET efficiency.
Availability
LT3685EDD#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial power supplies, set-top box power, and wall adapter replacement requiring stable component supply and long-term production continuity.
Supply support for LT3685EDD#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, industrial automation, communications, and automotive markets.
The LT3685EDD#TRPBF belongs to the LT® monolithic switching regulator product line, designed specifically for high-voltage, high-reliability DC/DC conversion in harsh environments including automotive, industrial, and telecom infrastructure.
FAQ
What is the absolute maximum input voltage rating for LT3685EDD#TRPBF?
The LT3685EDD#TRPBF has an absolute maximum VIN rating of 60V for non-repetitive 1-second transients, with continuous operation limited to 36V minimum and 40V maximum. Internal overvoltage protection disables switching when VIN exceeds 36V (min), allowing safe 60V transient survival without damage. This behavior is confirmed in the Absolute Maximum Ratings table and OVP section of the datasheet.
Does LT3685EDD#TRPBF require an external boost diode?
No, the LT3685EDD#TRPBF integrates a boost Schottky diode on-die, connected to the BD pin. This eliminates the need for an external diode in the bootstrap network. The BD pin must be connected to the anode of the external boost capacitor, and the diode's reverse leakage is specified at 0.02–2µA (VSW = 10V, VBD = 0V), per Electrical Characteristics Table.
What is the function of the VC pin on LT3685EDD#TRPBF?
The VC pin on LT3685EDD#TRPBF is the output of the internal error amplifier and directly controls peak switch current. Its voltage determines the current limit threshold via the VC-to-switch current gain of 3.5A/V. An RC network from VC to GND provides loop compensation, and the pin features an internal clamp at 2V to prevent saturation during overload, as detailed in the Pin Functions and Electrical Characteristics sections.
Can LT3685EDD#TRPBF synchronize to an external clock?
Yes, LT3685EDD#TRPBF supports external clock synchronization via the SYNC pin (Pin 6), accepting input frequencies from 250kHz to 2MHz. The SYNC pin has defined logic thresholds (0.5V low, 0.7V high) and <0.1µA bias current. When unused, SYNC must be grounded; clock edges require rise/fall times faster than 1µs for reliable operation, per the Applications Information section.
What thermal considerations apply to LT3685EDD#TRPBF in the DFN package?
The LT3685EDD#TRPBF in the 10-lead (3mm × 3mm) DFN package requires soldering of the exposed pad (Pin 11) to a PCB thermal plane for effective heat dissipation. Its thermal resistance is θJA = 45°C/W and θJC = 10°C/W. At 2A load with 12VIN/5VOUT, junction temperature rise is ~45°C above ambient - confirming suitability for 125°C max ambient operation when layout guidelines (thermal pad area, copper pour) are followed.
LT3685EDD#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):
- 36V
- Voltage - Output (Min/Fixed):
- 0.79V
- Voltage - Output (Max):
- 20V
- Current - Output:
- 2A
- Frequency - Switching:
- 200kHz ~ 2.4MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3685EDD#TRPBF FAQ
1.How can I place an order for LT3685EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3685EDD#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 LT3685EDD#TRPBF reliable?
The price and inventory of LT3685EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3685EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3685EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3685EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3685EDD#TRPBF?
LT3685EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3685EDD#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 LT3685EDD#TRPBF?
For technical support, including LT3685EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3685EDD#TRPBF requirements.
6.How does Aetrix verify that LT3685EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3685EDD#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 LT3685EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3685EDD#TRPBF?
All LT3685EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3685EDD#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 LT3685EDD#TRPBF part is unused and in its original packaging.
Return procedure for LT3685EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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