Features and Benefits
- Wide Input Range:
- Operation From 3.6V to 36V
- Overvoltage Lockout Protects Circuit through
- 60V Transients
- 2A Maximum Output Current
- Adjustable Switching Frequency: 200kHz to 2.4MHz
- Low Shutdown Current: IQ < 1µA
- Integrated Boost Diode
- Synchronizable Between 250kHz to 2MHz
- Power Good Flag
- Saturating Switch Design: 0.25Ω On-Resistance
- 0.790V Feedback Reference Voltage
- Output Voltage: 0.79V to 20V
- Soft-Start Capability
- Small 10-Pin Thermally Enhanced MSOP and (3mm x 3mm) DFN Packages
The LT3685 is an adjustable frequency (200kHz to 2.4MHz) monolithic step-down switching regulator that accepts input voltages up to 38V operating and 60V maximum. An internal overvoltage protection circuit turns off the power switch when VIN is above 38V typical (36V minimum) which then allows the part to safely withstand 60V transients. A high efficiency 0.25Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator, control, and logic circuitry. Current mode topology is used for fast transient response and good loop stability. The LT3685’s high operating frequency allows the use of small, low cost inductors and ceramic capacitors resulting in low output ripple while keeping total solution size to a minimum. The low current shutdown mode reduces input supply current to less than 1μA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good ﬂag signals when VOUT reaches 89% of the programmed output voltage. The LT3685 is available in 10-Pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.
- Automotive Battery Regulation
- Set Top Box
- Distributed Supply Regulation
- Industrial Supplies
- Wall Transformer Regulation
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (2)
Demonstration circuit 1212A-B is a monolithic step-dwon DC/DC switching regulatro featuring the LT3685 in the 3x3 DFN-10 package. The demo board provides 5V@2A from a 6.3V to 38V input and has transient protection up to 60V. The demo boards default switching frequency is 800kHz, but the LT3685 has a SYNC pin which allows frequency synchronization to an external clock over a 250kHz to 2MHz range. The LT3685's quiescent current is 0.9mA, while the LT3480 has a 70uA quiescent current.
An EMC filter at the input makes the circuit compatible with EMC standard EN55022 Class B.
Demonstration circuit 1167 is a monolithic step-down DC/DC switching regulator featuring the LT3685 in the MSOP-10 exposed pad package. The demo board provides 5V @ 2A from a 6.3V to 38V input and has transient protection up to 60V. The demo boards default switching frequency is 500kHz, but the LT3685 has a SYNC pin which allows frequency synchronization to an external clock over a 250kHz to 2MHz range.
Tools & Simulations
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.