9/2/2003
Edited by PETech Staff
DC-DC Controller
Linear Technology Corp.’s LT3804 is a secondary side dc-dc regulator with integrated optocoupler driver for dual-output isolated power supplies. Unlike previous dual-output isolated power supplies that require up to two dc-dc regulators and an external optocoupler driver, the LT3804 is a single controller solution housed in a small 28-lead TSSOP package. The LT3804 is ideal for converting 36V to 72V supplies to output voltages of 5V, 3.3V, 2.5V, 1.8V, 1.5V and lower at up to 50W per output. Differential Kelvin voltage sensing is used for each output feedback to achieve high regulation accuracy and design simplicity. When combined with Linear Technology's primary side dc-dc regulators, the LT3804 offers a complete isolated dual output power supply priced up to 40% below comparable dc-dc modules. Applications include 48V distributed power, datacom/telecom, DSL/cable modems, servers and RAID systems, as well as industrial and automotive instruments.
The LT3804 contains an error amplifier and an optocoupler driver to regulate the main output. For the second output regulation, the IC 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 device 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. The LT3804 operates with switching frequencies ranging from 200 kHz to 800 kHz.
For more information, visit www.linear.com.