Datasheet

13
LTC3410
3410fb
APPLICATIO S I FOR ATIO
WUUU
Figure 6a
Figure 6b Figure 6c
I
LOAD
(mA)
0.1
0
10
20
30
40
EFFICIENCY (%)
50
60
70
80
90
100
10 1001 1000
3410 F06b
V
IN
= 3.6V
V
IN
= 4.2V
V
OUT
100mV/DIV
AC COUPLED
I
L
200mA/DIV
I
LOAD
200mA/DIV
20µs/DIV
3410 F06c
V
IN
= 3.6V
V
OUT
= 3V
I
LOAD
= 100mA TO 300mA
Substituting V
OUT
= 3V, V
IN
= 4.2V, I
L
= 100mA
and f = 2.25MHz in Equation (3) gives:
L
V
MHz mA
V
V
H=
=
3
2 25 100
1
3
42
38
.().
. µ
A 4.7µH inductor works well for this application. For best
efficiency choose a 350mA or greater inductor with less
than 0.3 series resistance.
C
IN
will require an RMS current rating of at least 0.125A
I
LOAD(MAX)
/2 at temperature and C
OUT
will require an ESR
of less than 0.5. In most cases, a ceramic capacitor will
satisfy this requirement. From Table 2, Capacitance Selec-
tion, C
OUT
= 10µF and C
IN
= 4.7µF.
For the feedback resistors, choose R1 = 301k. R2 can
then be calculated from equation (2) to be:
R
V
R k use k
OUT
2
08
1 1 827 8 825=
=
.
.;
Figure 6 shows the complete circuit along with its
efficiency curve.
V
IN
C
IN
††
4.7µF
CER
V
IN
2.7V
TO 4.2V
LTC3410
RUN
3
4.7µH*
10pF
825k
301k
3410 F06a
6
4
1
2, 5
SW
V
FB
GND
C
OUT
10µF
CER
V
OUT
3V
TAIYO YUDEN JMK212BJ106
††
TAIYO YUDEN JMK212BJ475
*MURATA LQH32CN4R7M23