DESCRIPTION
Demonstration circuit 927 is a high
density 5V/4A and 3.3V/4A step down
converter featuring the LT3742. A
500kHz fixed frequency current mode
architecture provides fast transient
response with simple loop compensa-
tion components and cycle-by-cycle
current limiting. An internal step-up
regulator is used to generate the
gate drive voltage, allowing the gate
of the external high side N-channel
MOSFET to be driven to full enhance-
ment for the highly efficient opera-
tion. The dual channels operate 180
O
out of phase to reduce the input rip-
ple current, minimizing the noise in-
duced on the input supply, and allow-
ing the use of less input capaci-
tance. The device also includes indi-
vidual shutdown and power-good output
for each converter. The LT3742 is
available in a small 4mm x 4mm QFN
package.
The LT3742 datasheet gives a complete
description of the part, operation
and application information. The
datasheet must be read in conjunction
with this quick start guide for demo
circuit 927.
Design files for this circuit board
are available. Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technol-
ogy Corporation. ThinSOT and PowerPath are trademarks of Lin-
ear Technology Corporation.
Table1. Performance Summary ( T
A
= 25
o
C )
PARAMETER CONDITION VALUE
Minimum Input Voltage 5.5V
Maximum Input Voltage 28V (Note 1)
Output Voltage V
OUT1
5V +/-3%
Output Voltage V
OUT2
3.3V +/-3%
Maximum Output Current I
OUT1
4A
Maximum Output Current I
OUT2
4A
Typical Switching Frequency 500kHz
Note 1:
See “Input Voltage Range” section in the datasheet for detail
.
Dual, 2-Phase Step-
Switching
