ltc3405es6 Linear Technology Corporation, ltc3405es6 Datasheet - Page 13

• Manufacturer Part Number: ltc3405es6
• Description: 1.5mhz, 300ma Synchronous Step-down Regulator In Thinsot
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Substituting V
f = 1.5MHz in equation (3) gives:
For best efficiency choose a 300mA or greater inductor
with less than 0.3Ω series resistance.
C
I
of less than 0.6Ω and greater than 0.1Ω. In most cases,
a tantalum capacitor will satisfy this requirement.
TO 4.2V
TYPICAL APPLICATIO S
LOAD(MAX)
IN
2.7V
V
L
will require an RMS current rating of at least 0.125A ≅
IN
=
1 5
.
C
2.2µF
CER
MHz
IN
/2 at temperature and C
100
†
90
80
70
60
50
40
30
0.1
2 5
OUT
.
(
4
1
6
100
V
V
IN
V
RUN
MODE
= 4.2V
IN
= 2.5V, V
LTC3405
U
mA
GND
OUTPUT CURRENT (mA)
1
2
)
SW
V
Figure 11a
V
FB
⎛
⎜
⎝
IN
1
U
= 2.7V
3
5
−
10
IN
TO 4.2V
2 5
4 2
412k
6.8µH*
3405 F11a
2.7V
V
= 4.2V, ∆I
.
.
22pF
887k
V
IN
IN
V
V
= 3.6V
OUT
U
100
⎞
⎟ ≅
⎠
W
** AVX TPSB336K006R0600
*SUMIDA CMD4D11-6R8MC
†
Optimized for Small Footprint and High Efficiency
3405 TA01b
TAIYO YUDEN LMK212BJ225MG
will require an ESR
C
1µF
CER
+
6 8
IN
.
**
1000
L
µ
Single Li-Ion to 1.8V/300mA Regulator
C
33µF
TANT
= 100mA and
H
OUT
4
1
6
**
V
2.5V
V
RUN
MODE
U
OUT
IN
LTC3405
GND
2
V
SW
FB
3
5
1M
200k
3405 TA01a
4.7µH*
For the feedback resistors, choose R1 = 412k. R2 can
then be calculated from equation (2) to be:
Figure 11 shows the complete circuit along with its
efficiency curve.
22pF
332k
**
*
†
MURATA LQH3C4R7M34
TAIYO YUDEN CERAMIC JMK107BJ105MA
TAIYO YUDEN CERAMIC JMK212BJ475MG
R
2
AC COUPLED
100mV/DIV
200mA/DIV
200mA/DIV
=
⎛
⎜
⎝
I
V
V
LOAD
OUT
0 8
100
OUT
C
4.7µF
CER
90
80
70
60
50
40
30
I
OUT
.
L
0.1
V
1.8V
V
I
OUT
LOAD =
†
IN
−
V
= 3.6V
IN
1 1 875 5
= 4.2V
100mA TO 250mA
⎞
⎟
⎠
R
OUTPUT CURRENT (mA)
1
V
=
IN
Figure 11b
= 2.7V
V
40µs/DIV
IN
= 3.6V
10
. ;
k use
100
3405 TA01c
3405 F11b
8
87k
1000
LTC3405
13
3405fa