Secondary Side Dual Output Controller with Opto Driver

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.

Applications

* 48V Input Isolated DC/DC Converters

* Multiple Output Power Supplies

* Offline Converters

* DC/DC Power Modules

* Regulates Two Secondary Outputs

* Optocoupler Feedback Driver and Second Output Synchronous Driver Controller

* True Differential Remote Sensing Regulation

* High Switching Frequency: up to 800kHz

* Programmable Current Limit

* Programmable Soft-Start and Power Good

* Automatic Frequency Synchronization

* Available in Thermally Enhanced 28-Lead TSSOP