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The LT1618 is a step-up DC/DC converter designed by Analog Devices' that provides constant-current and constant-voltage output at a frequency of 1.4 MHz.
The LT1618 uses a combination of a traditional voltage feedback loop and a unique current feedback loop to operate as a source of constant-current and constant-voltage. This current mode switcher has a wide input voltage range of 1.6 V to 18 V, and its high switching frequency of 1.4 MHz allows the use of small, low-profile inductors and capacitors. The current sense voltage is set to 50 mV and can be adjusted using the IADJ pin.
The LT1618 is available in two package options: the 10-pin exposed pad DFN and the 10-pin MSOP packages. These package options provide a complete solution for constant-current applications.
Demonstration circuit DC780B is an example of the LT1618 being used as a constant-current, constant-voltage step-up DC/DC converter. DC780B is a general-purpose boost converter that generates a 12 V, 250 mA output from a 3.3 V to 4.2 V input source. Moreover, DC780B can function as an LED driver, where the Luxeon LED (not included) is regulated at a current of 500 mA (default current) and a forward voltage of 3.5 V. By changing the value of R4 to 2.2 M, the LED current can be regulated at 250 mA. Although the LT1618 can operate with wider input voltages, the output voltage level and component selection of this demo circuit restricts its application to Lithium-ion battery input levels.
Accurate input/output current control: ±5% overtemperature
Accurate output voltage control: ±1%
Wide VIN range: 1.6 V to 18 V
1.4 MHz switching frequency
High output voltage: up to 35 V
Low VCE(SAT) switch: 200 mV at 1 A
Available in (3 mm x 3 mm x 0.8 mm) 10-pin DFN and 10-pin MSOP packages
LED backlight drivers
USB powered boost/SEPIC converters
Input current limited boost/SEPIC converters
Battery chargers
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