Linear Technology 1060 Quick Start Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1060
DESCRIPTION
Demonstration circuit 1060 features two LT3508
step-down DC/DC switching converters. One circuit
uses the LT3508EFE and the other circuit has the
LT3508EUF. The LT3508 dual output step-down
switching regulator has two internal power
switches, a wide input voltage range, adjustable
switching frequency synchronizable over the fre-
quency range, programmable soft-start, tracking,
power-good, and channel sequencing. The anti-
phase switching reduces the input capacitor. The
wide V range of the LT3508 allows step-down
IN
configurations with up to 36V input. The high power
internal switches have current limit that allows for
up to 1.4A output on each output.
The demonstration circuit has two circuits. The top
is optimized for high efficiency, wide input range
and maximum output current; the bottom is opti-
mized for the size. The top circuit is rated for 3.3V
at 1.4A and 5V at 1.4A output from a 6V–36V input
using the FE package. The frequency is set to
700kHz to allow for the high VIN to VOUT ratio and
provides high efficiency throughout the range. The
bottom circuit generates 1.8V at 1A and 3.3V at 1A
from a 5V to 16V DC input using the QFN package
and shows off the compact size with 1.6MHz
DUAL MONOLITHIC STEP-DOWN SWITCHING REGULATOR
switching frequency. The two channels are se-
quenced so that the 1.8V channel starts before the
3.3V channel. The two circuits are completely iso-
lated from each other and can be run simultane-
ously or independently. The shutdown terminals are
available on each circuit as are the power good and
track terminals in case sequencing or tracking is
preferred.
This board is designed for applications that require
two step-down converters up to 1.4A load with low
cost, small board space, low parts count, and sim-
ple circuit design. The high current, on-board, dual
monolithic switches eliminate the need for external
switches. The current-mode control simplifies the
compensation network and gives excellent transient
response.
Please read the LT3508 datasheet in addition to this
quickstart guide for details regarding LT3508 opera-
tion and applications.
Design files for this circuit board are available.
Call the LTC factory.
LT is a trademark of Linear Technology Corporation
LT3508
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