1
dc1428af
DEMO MANUAL DC1428A
DESCRIPTION
LT3645
0.5A, 36V Step-Down
Regulator with LDO
Demonstration circuit 1428A features the LT
®
3645. The
circuit is designed to convert a 5V to 36V input source to
3.3V at 300mA and 2.5V at 200mA. JP1 and JP2 enable and
disable the 3.3V output and the 2.5V output respectively.
LDO only operates if both, EN/UVLO and EN2 are greater
than 1.2V. Demo board includes an optional resistor, R8,
for easy implementation of UVLO. The LT3645 data sheet
gives a complete description of the part, its operation and
L
, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
application information. The data sheet must be read in
conjunction with this quick start guide for working on or
modifying the demo circuit 1428A.
Design files for this circuit board are available at
http://www.linear.com/demo
(T
A
= 25°C)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input Supply Range
5
36
V
3.3V
OUT
Buck Output Voltage Accuracy
V
IN
= 5V to 36V, I
LOAD
= 500mA
3.226
3.3
3.374
V
2.5V
OUT
LDO Output Voltage Accuracy
V
IN
= 5V to 36V, I
LOAD
= 200mA
2.444
2.5
2.556
V
Efficiency
V
IN
= 5V, I
LOAD
= 500mA for Buck, 0mA for LDO
83
%
V
IN
= 5V, I
LOAD
= 300mA for Buck, 200mA for LDO
75
%
Buck V
OUT
Ripple
V
IN
= 5V, I
LOAD
= 500mA
10
mV
LDO V
OUT
Ripple
V
IN
= 5V to 36V, I
LOAD
= 200mA
1
mV
f
S
Switching Frequency
750
kHz
