Datasheet

LTC3602
15
3602fb
APPLICATIONS INFORMATION
capacitance and a ceramic capacitor in parallel to lower
the total effective ESR. For this design, a 100μF ceramic
capacitor will be used. C
IN
should be sized for a maximum
current rating of:
IA
V
V
V
V
A
RMS RMS
==25
33
8 4
8 4
33
1122.•
.
.
•
.
.
–.
Decoupling the PV
IN
pin with a 22μF ceramic capacitor is
adequate for most applications.
The output voltage can now be programmed by choosing
the values of R1 and R2. Chose R1 = 105k and calculate
R2 as:
R2=R1
V
OUT
0.6V
–1
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
= 472.5k
Choose a standard value of R2 = 475k. The voltage on
the MODE pin will be set to 0.6V by tying the MODE pin
to the FB pin. This will set the burst current equal to ap-
proximately 1A. Figure 6 shows a complete schematic for
this design example.
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3602. Check the following in your layout:
1. A ground plane is recommended. If a ground plane layer
is not used, the signal and power grounds should be
segregated with all small signal components returning
to the SGND pin at one point which is then connected
to the PGND pin close to the LTC3602.
2. Connect the (+) terminal of the input capacitor(s), C
IN
, as
close as possible to the PV
IN
pin. This capacitor provides
the AC current into the internal power MOSFETs.
3. Keep the switching node, SW, away from all sensitive
small signal nodes.
4. Flood all unused areas on all layers with copper. Flooding
with copper will reduce the temperature rise of power
components. You can connect the copper areas to any
DC net (PV
IN
, INTV
CC
, V
OUT
, PGND, SGND, or any other
DC rail in your system).
Figure 6. 8.4V to 3.3V, 2.5A Regulator at 1MHz, Burst Mode Operation
C
IN
22μF
V
IN
8.4V
V
OUT
3.3V
2.5A
3602 F06
D1
L1
2.2μH
R
OSC
105k
R
ITH
4.32k
R1
105k
R
PG
200k
L1: VISHAY IHLP2525CZER2R2MO1
C
IN
: TAIYO YUDEN TMK325BJ226MM-T
C
OUT:
TDK C3225X5ROJ107M
C
VCC
1μF
C
ITH
1nF
C
OUT
100μF
SYNC/MODE
PGOOD
R
T
I
TH
V
FB
RUN
TRACK/SS
PGND
INTV
CC
PV
IN
BOOST
SW
SW
SW
PGND
PGND
LTC3602
R2
475k
C
BST
0.22μF
PGOOD
C
FB
22pF