LTC3624/LTC3624-2
16
36242fd
For more information www.linear.com/LTC3624
Design Example
As a design example, consider using the LTC3624/LTC3624-2
in an application with the following specifications:
V
IN
= 10.8V to 13.2V
V
OUT
= 3.3V
I
OUT(MAX)
= 2A
I
OUT(MIN)
= 0A
f
SW
= 2.25MHz
Because efficiency and quiescent current are important at
both 500mA and 0A current states, Burst Mode operation
will be utilized.
Given the internal oscillator of 2.25MHz, we can calcu
-
late the inductor value for about 40% ripple current at
maximum V
IN
:
L =
3.3V
2.25MHz • 0.8A
1–
3.3V
13.2V
=1.38µH
Given this, a 1.5µH inductor would suffice.
C
OUT
will be selected based on the ESR that is required to
satisfy the output voltage ripple requirement and the bulk
capacitance needed for loop stability. For this design, a
47µF ceramic capacitor will be used.
C
IN
should be sized for a maximum current rating of:
I
RMS
=2A
3.3V
13.2V
13.2V
3.3V
–1
1/2
=0.86A
Bypassing the V
IN
pin to ground with 10µF ceramic capaci-
tors is adequate for most applications.
applicaTions inForMaTion
Figure 3a. Sample PCB Layout-Top Side Figure 3b. Sample PCB Layout-Bottom Side
TOP LAYER
GND
GND
GND
C
IN
C
IN
V
IN
V
OUT
C
OUT
C_INTVCC
L1
LTC3624
BOTTOM LAYER
GND
GND
GND
C
IN
V
IN
V
OUT
C
OUT
(OPT)
C
OUT
(OPT)
