DC1144A-B: -12V @ 350mA, 5 ~ 12V in, Inverting

Demonstration circuits 1144A-A and 1144A-B feature the LT3580EDD in Boost/Inverting Regulator configurations. The demo circuits demonstrate small size and low component count. The boost is designed to convert a 3 – 10 V source to 12 V at 300 mA while the inverter converts a 5 – 12 V source to -12 V at 350 mA. Both converters use only one feedback resistor to set the output voltage.

The LT3580 operates with inputs as high as 32 V but in these demo boards the input is limited by the voltage rating of the input capacitors and the magnitude of the boost output. In a boost converter the input needs to be less than the output.

Care must be taken when operating the LT3580 at high input voltages as the junction temperature increases due to higher internal dissipation. Higher switching frequencies also increase the internal dissipation.

The LT3580 gets powered from the main input in both, DC1144A-A and DC1144A-B, but there is an option for a linear regulator built into the board that will allow the IC to be powered from a lower voltage. If this option is used, just cut the trace as shown in figure 6 and install the optional emitter follower on the back of the board.

The DC1144A-B can easily be configured into a SEPIC converter, just switch the positions of L2 and D2 as shown in figure 6.

The LT3580 includes many other features such as synchronization to external clock, user configurable undervoltage lockout, soft-start, frequency foldback, and it is easily as a boost or inverter converter.

These circuits are intended for space-conscious applications such as local bus supplies, TFT-LCD bias supplies, GPS receivers, VFD bias supplies, and DSL modems.