DC780B: 12V @ 250mA, 3.3 ~ 4.2V in, Boost

Summary

Demonstration circuit 780B is a Constant-Current Constant-Voltage 1.4MHz Step-up DC/DC Converter featuring the LT®1618. DC780B demonstrates a general purpose Boost converter with a 12V, 250mA output from a 3.3V-4.2V source.

The demo board can also be used as an LED driver, where a Luxeon LED (not installed), is driven with a regulated current of 500mA (default current), at a forward voltage of 3.5V. By changing the value or R4 to 2.2M the LED current can be regulated at 250mA.

The LT1618 can be used for wider input voltages, but output voltage level and component selection restrict this demo circuit to Lithium Ion battery input levels.

The LT1618 contains a unique current feedback loop that allows for accurate regulation of either input or output current, whether in Boost, or SEPIC topology.

The data sheet gives a complete description of the device, operation and application information. The data sheet must be read in conjunction with this demo manual for DC780B.

Specifications

Manufacturer	Analog Devices Inc.
Category	AC/DC and DC/DC Conversion
Sub-Category	DC/DC SMPS - Single Output
Eval Board Part Number	DC780B-ND
Eval Board Supplier	Analog Devices Inc.
Eval Board	Normally In Stock
Topology	Step Up
Outputs and Type	1 Non-Isolated
Voltage Out: Factory Set	12 V
Current Out	250 mA
Voltage In	3.3 ~ 4.2 V
Efficiency @ Conditions	>79%, 4.2V in, 12V @ 50 ~ 350 mA >75%, 3.3V in, 12V @ 50 ~ 250 mA
Voltage Out Range	11.64 ~ 12.36 V
Features	Current Limit (Adj. or Fixed) Shutdown, Enable, Standby
Switching Frequency	1.4 MHz
Standby Current [Typical]	100 nA
Quiescent Current [Typical]	1.8 mA
Component Count + Extras	14 + 8
Internal Switch	Yes
Design Author	Linear Technology
Application / Target Market	Battery Chargers LCD Backlighting Power: Auxiliary Power Supply USB Powered Devices
Standby Current [Maximum]	1 µA
Quiescent Current [Maximum]	2.7 mA
Main I.C. Base Part	LT1618
Date Created By Author	2016-04
Date Added To Library	2016-12