Analog Devices

The LT3680 is an adjustable frequency (200kHz to 2.4MHz) monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 95mΩ 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. Low ripple Burst Mode®operation maintains high efficiency at low output currents while keeping output ripple below 15mV in a typical application. In addition, the LT3680 can further enhance low output current efficiency by drawing bias current from the output when VOUTis above 3V. Shutdown 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 VOUTreaches 91% of the programmed output voltage. The LT3680 is available in 10-Pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.ApplicationsAutomotive Battery RegulationPower for Portable ProductsDistributed Supply RegulationIndustrial SuppliesWall Transformer Regulation

The LT3681 is an adjustable frequency (300kHz to 2.8MHz) monolithic buck switching regulator that accepts input voltages up to 34V (36V maximum). A high efficiency 0.18Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator, control, and logic circuitry. An undedicated power Schottky diode is integrated into the LT3681 to minimize the solution size. Current mode topology is used for fast transient response and good loop stability. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15mV in a typical application. In addition, the LT3681 can further enhance low output current efficiency by drawing bias current from the output when VOUTis above 3V. Shutdown 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 VOUTreaches 90% of the programmed output voltage. The LT3681 is available in 14-Pin 4mm x 3mm DFN package with exposed pads for low thermal resistance.ApplicationsAutomotive Battery RegulationPower for Portable ProductsDistributed Supply RegulationIndustrial SuppliesWall Transformer Regulation

The LT3684 is an adjustable frequency (300kHz to 2.8MHz) monolithic buck switching regulator that accepts input voltages up to 34V (36V maximum). A high efficiency 0.18Ω 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 LT3684’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 VOUTreaches 90% of the programmed output voltage. The LT3684 is available in 10-Pin MSOP and 3mm × 3mm DFN packages with Exposed Pads for low thermal resistance.ApplicationsAutomotive Battery RegulationPower for Portable ProductsDistributed Supply RegulationIndustrial SuppliesWall Transformer Regulation

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 VINis 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 VOUTreaches 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.ApplicationsAutomotive Battery RegulationSet Top BoxDistributed Supply RegulationIndustrial SuppliesWall Transformer Regulation

The LT3686A is a current mode PWM step-down DC/DC converter with an internal power switch. The wide input range of 3.6V to 37V makes the LT3686A suitable for regulating power from a wide variety of sources, including 24V industrial supplies and automotive batteries. Its high maximum frequency allows the use of tiny inductors and capacitors, resulting in a very small solution. Operating frequency above the AM band avoids interfering with radio reception, making the LT3686A particularly suitable for automotive applications.Cycle-by-cycle current limit, thermal shutdown and DA current sense provide protection against fault conditions. Soft-start and frequency foldback eliminate input current surge during start-up. An optional internal regulated active load at the output via the BD pin keeps the LT3686A at full switching frequency at light loads, resulting in low, predictable output ripple above the audio and AM bands. Internal compensation and an internal boost diode reduce external component count.The LT3686A offers external synchronization capability, whereas the LT3686 does not.Overvoltage ProtectionsFeaturesLT368655V-LT3686A60VExternal SynchronizationApplicationsAutomotive SystemsBattery-Powered EquipmentWall Transformer RegulationDistributed Supply Regulation

The LT3688 is an adjustable frequency (350kHz to 2.2MHz) dual monolithic step-down switching regulator with two power-on reset timers and a watchdog timer. The regulator operates off inputs up to 36V. Low ripple Burst Mode®operation maintains high efficiency at low output current while keeping output ripple below 25mV in a typical application, with input quiescent current of just 115μA. Shutdown circuitry reduces input supply current to less than 1μA while EN/UVLO is pulled low.The reset and watchdog timeout periods are both adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation without false triggering. The open collectorRSTpins will pull down if the monitored output voltage drops 10% below the programmed value. The LT3688 watchdog timer monitors for watchdog falling edges grouped too close together or too far apart.The LT3688 is available in 24-Pin TSSOP and 4mm × 4mm QFN packages, each with an exposed pad for low thermal resistance.ApplicationsAutomotive Electronic Control UnitsIndustrial Power SuppliesHigh-Reliability μProcessor Systems

The LT3689 is an adjustable frequency (350kHz to 2.2MHz) monolithic step-down switching regulator with a power-on reset and watchdog timer. The regulator operates from inputs up to 36V and withstands transients up to 60V. Low ripple Burst Mode®operation maintains high efficiency at low output current while keeping output ripple below 15mV in a typical application, with input quiescent current of just 85μA. Shutdown circuitry reduces input supply current to less than 1μA while EN/UVLO is pulled low. Using a resistor divider on the EN/UVLO pin provides a programmable undervoltage lockout. Current limit, frequency foldback and thermal shutdown provide fault protection.The reset and watchdog timeout periods are independently adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation of a system without false triggering. The open collectorRSTwill pull down if output voltage drops 10% below the programmed value. The watchdog timer is pin-selectable for window or timeout modes. In timeout mode,WDOpulls low if too long of a period passes before a watchdog transition is detected. In window mode, the LT3689 monitors for WDI falling edges grouped too close together or too far apart.ApplicationsAutomotive Electronic Control UnitsIndustrial Power Supplies

The LT®3690 is an adjustable frequency monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 90mΩ switch is included on the device along with the boost diode and the necessary oscillator, control, and logic circuitry. The internal synchronous power switch of 30mΩ increases efficiency and eliminates the need for an external Schottky catch diode. Current mode topology is used for fast transient response and good loop stability. Shutdown reduces input supply current to less than 1µA. The low ripple Burst Mode maintains high efficiency at low output currents while keeping output ripple below 15mV in typical applications.The LT3690 features robust operation and is easily configurable. Using a resistor divider on the UVLO pin provides a programmable undervoltage lockout. A power good flag signals when VOUTreaches 90% of the programmed output voltage. Protection circuitry senses the current in the power switches to protect the LT3690 against short-circuit conditions. Frequency foldback and thermal shutdown provide additional protection. The LT3690 is available in a 4mm × 6mm QFN package with exposed pads for low thermal resistance.ApplicationsAutomotive SystemsIndustrial SuppliesDistributed Supply Regulation

The LT3692A is a dual current mode PWM step-down DC/DC converter with two internal 3.8A switches. Independent input voltage, shutdown, feedback, soft-start, UVLO current limit and comparator pins for each channel simplify complex power supply tracking and sequencing requirements.To optimize efficiency and component size, both converters have a programmable maximum current limit and are synchronized to either a common external clock input, or a resistor settable fixed 250kHz to 2.25MHz internal oscillator. A frequency divider is provided for channel 1 to further optimize component size. At all frequencies, a 180° phase relationship between channels is maintained, reducing voltage ripple and component size. A clock output is available for synchronizing multiple regulators.Minimum input to output voltage ratios are improved by allowing the switch to stay on through multiple clock cycles only switching off when the boost capacitor needs recharging. Independent channel operation can be programmed using the SHDN pin. Disabling both converters reduces the total quiescent current to <10μA.The LT3692A is an improved version of the LT3692 with reduced minimum on-time.Min On-TimeFeaturesPackageLT3692180ns-5 × 5 QFN-32LT3692A140nsProgrammable Shutdown UVLOTSSOP-38E, 5 × 5 QFN-32ApplicationsAutomotive SuppliesDistributed Supply Regulation

The LT3693 is an adjustable frequency (200kHz to 2.4MHz) monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 95mΩ 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. Shutdown 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 VOUTreaches 91% of the programmed output voltage. The LT3693 is available in 10-Pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.ApplicationsAutomotive Battery RegulationPower for Portable ProductsDistributed Supply RegulationIndustrial SuppliesWall Transformer Regulation