USB 5V to 12V DC-DC Step-Up Converter by LT1618

This circuit is a 5v to 12 DC-DC step-up converter circuit which is specially ideal for the usb powered applications.
A usb has two current supply modes.Before deecting the connected device the maximum supplies is 100mA to the load.when
recognizing device its increases the output current up to 500mA.the controller (LT1618) also provides two input currents modes
100mA and 500mA which is selected by the user.


Output currents are limited due to the increased potential difference at the output. When the demand of the
load increases, output voltage will start to decrease. For example, if the circuit operates in the 100 mA
input mode, when the load is 35 mA, the output voltage will be kept at 12V. But if the load increases to 50 mA,
output voltage will reduce to 8V to maintain the constant 100 mA input current.