LTC3624_15 Datasheet, PDF (16/20 Pages) Linear Technology – 17V, 2A Synchronous Step-Down Regulator with 3.5A Quiescent Current

LTC3624/LTC3624-2
Applications Information
7. Flood all unused areas on all layers with copper, which
reduces the temperature rise of power components.
These copper areas should be connected to GND.
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.
TOP LAYER
GND
V_IN
C_IN
LTC3624
C_IN
L1
C_OUT
C_INTVCC
V_OUT
GND
GND
V_IN
C_IN
GND
BOTTOM LAYER
GND
C_OUT
(OPT)
V_OUT
C_OUT
(OPT)
GND
Figure 3a. Sample PCB Layout-Top Side
36242 F03a
Figure 3b. Sample PCB Layout-Bottom Side
36242 F03b
16
For more information www.linear.com/LTC3624
36242fc