Analog Devices Inc./Maxim Integrated

The LT3796/LT3796-1 are DC/DC controllers designed to regulate a constant-current or constant-voltage and are ideal for driving LEDs. The fixed frequency and current mode architecture result in stable operation over a wide range of supply and output voltages. Two ground referred voltage FB pins serve as the input for several LED protection features, and also allow the converter to operate as a constant-voltage source. The LT3796/LT3796-1 feature a programmable threshold output current sense amplifier with rail-to-rail common mode range. A separate high side amplifier is gain configurable with two resistors and can be used to regulate a second current or a voltage in combination with one of the FB pins. The PWM input provides LED dimming ratios of up to 3000:1.The LT3796-1 is optimized for a second output current regulation loop that can be enabled/disabled with a PMOS switch, either to drive a second LED string or to extend analog dimming range.ApplicationsHigh Power LED, High Voltage LED, Dual StringBattery and SuperCap ChargersAccurate Current Limited Voltage Regulators

The LT3797 is a triple output DC/DC controller designed to drive three strings of LEDs. The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. The LT3797 includes an integrated DC/DC converter to produce a regulated 7.5V supply for the N-channel MOSFET gate drivers of the three channels. This high efficiency converter enables the part to operate from a wide input voltage range from 2.5V to 40V.The LT3797 is designed so that each converter can use the most suitable configuration to drive its LED load, whether step-up, step-down or a combination. Two key features enable this flexibility: first the LT3797 can sense output current at the high side of the LED string; and second, the voltage feedback pin, FBH, is referred to the ISP current sensing input. The CTRL inputs provide output current analog dimming capability. The TG drivers level shift the PWM signals to drive the gates of external LED-disconnect P-channel MOSFETs, allowing high PWM dimming range, and providing LED overcurrent protection and short-circuit protected boost capability.ApplicationsAutomotive and Industrial LightingRGB LightingBillboards and Large Displays

The LT3799 is an isolated flyback controller with power factor correction specifically designed for driving LEDs. The controller operates using critical conduction mode allowing the use of a small transformer. Using a novel current sensing scheme, the controller is able to deliver a well regulated current to the secondary side without using an opto-coupler. A strong gate driver is included to drive an external high voltage MOSFET. Utilizing an onboard multiplier, the LT3799 typically achieves power factors of 0.97. TheFAULTpin provides notification of open and short LED conditions.The LT3799 uses a micropower hysteretic start-up to efficiently operate at offline input voltages, with a third winding to provide power to the part. An internal LDO provides a well regulated supply for the part’s internal circuitry and gate driver.TRIAC DimmableLED Current RegulationLT3799YES±10%LT3799-1NO±5%ApplicationsOffline 4W to 100W+ LED ApplicationsHigh DC VINLED Applications

The LT3799-1 is an isolated flyback controller with power factor correction specifically designed for driving LEDs. The controller operates using critical conduction mode allowing the use of a small transformer. Using a novel current sensing scheme, the controller is able to deliver a well regulated current to the secondary side without using an opto-coupler. A strong gate driver is included to drive an external high voltage MOSFET. Utilizing an onboard multiplier, the LT3799-1 typically achieves power factors of 0.97. TheFAULTpin provides notification of open and short LED conditions. The LT3799-1 offers improved line regulation over the LT3799, but is not designed for use with a TRIAC dimmer.The LT3799-1 uses a micropower hysteretic start-up to efficiently operate at offline input voltages, with a third winding to provide power to the part. An internal LDO provides a well regulated supply for the part’s internal circuitry and gate driver.Triac DimmableLED Current RegulatorLT3799Yes± 10%LT3799-1No± 5%ApplicationsOffline 4W to 100W+ LED ApplicationsHigh DC VINLED Applications

The LT3800 is a 200kHz fixed frequency high voltage synchronous current mode step-down switching regulator controller. The IC drives standard gate N-channel power MOSFETs and can operate with input voltages from 4V to 60V. An onboard regulator provides IC power directly from VINand provides for output-derived power to minimize VINquiescent current. MOSFET drivers employ an internal dynamic bootstrap feature, maximizing gate-source "ON" voltages during normal operation for improved operating efficiencies. The LT3800 incorporates Burst Mode operation, which reduces no load quiescent current to under 100µA. Light load efficiencies are also improved through a reverse inductor current inhibit, allowing the controller to support discontinuous operation. Both Burst Mode operation and the reverse-current inhibit features can be disabled if desired. The LT3800 incorporates a programmable soft-start that directly controls the voltage slew rate of the converter output for reduced startup surge currents and overshoot errors. The LT3800 is available in a 16-lead thermally enhanced TSSOP package.Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258.Applications12V and 42V Automotive and Heavy Equipment48V Telecom Power SuppliesAvionics and Industrial Control SystemsDistributed Power Converters

The LT3804 is a high efficiency step-down switching regulator with optocoupler feedback control for regulating multiple outputs in single-secondary winding isolated power supplies.The LT3804 contains an error amplifier and an optocoupler driver to regulate the first (main) output. For the second output regulation, the LT3804 contains a complete PWM controller to drive dual synchronous N-channel MOSFETs. With leading edge modulation, it operates with either current or voltage mode control of the primary side. The LT3804 is synchronized to the falling edge of the transformer secondary winding and can be used in single ended or double-ended isolated power converter topologies. A user selectable discontinuous conduction mode improves light load efficiency.True differential Kelvin sensing is used for each output feedback amplifier to achieve high regulation accuracy and design simplicity. Other features include soft start, current limit and power good flags.Applications48V Input Isolated DC/DC ConvertersMultiple Output Power SuppliesOffline ConvertersDC/DC Power Modules

The LT3825 is an isolated switching regulator controller designed for medium power flyback topologies. A typical application is 10W to 60W with input voltage limited only by external power path components. A third transformer winding provides output voltage feedback.The LT3825 is a current mode controller that regulates output voltage based on sensing secondary voltage via a transformer winding during flyback. This allows for tight output regulation without the use of an opto-isolator, improving dynamic response and reliability. Synchronous rectification increases converter efficiency and improves output cross regulation in multiple output converters.The LT3825 operates in forced continuous conduction mode which improves cross regulation in multiple winding applications. Switching frequency is user programmable and can be externally synchronized. The part also has load compensation, undervoltage lockout and soft-start circuity.ApplicationsIsolated Medium Power (10W to 60W) SuppliesIsolated Telecom, Medical ConvertersInstrumentation Power SuppliesIsolated Power over Ethernet Supplies