Features

• 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: I_Q < 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

Typical Application

Description

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 V_IN is above 38V typical (36V minimum) which then allows the part to safely withstand 60V transients. A high efficiency 0.25 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 V_OUT reaches 86% 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.