ltc3405a-1.375 Linear Technology Corporation, ltc3405a-1.375 Datasheet - Page 11

• Manufacturer Part Number: ltc3405a-1.375
• Description: 1.375v, 1.5mhz, 300ma Synchronous Step-down Regulators In Thinsot
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Substituting V
f = 1.5MHz in equation (3) gives:
TO 4.2V
For best efficiency choose a 200mA or greater inductor
with less than 0.3Ω series resistance.
C
≅ I
ESR of less than 0.5Ω. In most cases, a ceramic capacitor
will satisfy this requirement.
Figure 5 shows the complete circuit along with its effi-
ciency curve.
IN
2.7V
L
V
LOAD(MAX)
will require an RMS current rating of at least 0.125A
IN
=
1 5
V
.
OUT
Figure 4. LTC3405A-1.375 Suggested Layout
C
2.2µF
CER
MHz
IN
1 375
***
Figure 5a. Small Footprint Application
L1
.
/2 at temperature and C
OUT
(
60
4
1
6
SW
V
= 1.375V, V
mA
V
LTC3405A-1.375
RUN
MODE
PIN 1
IN
U
C
GND
)
OUT
⎛
⎜
⎝
2
1
3405A1375 F05a
U
V
−
LTC3405A-1.375
OUT
SW
1 375
VIA TO V
.
4 2
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
GND
*** MURATA 0603 GRM188R61A225KE34B
IN
3
5
** MURATA 0603 GRM188R60G106ME47B
.
* MURATA LQHMCN10002
= 4.2V, ∆I
V
10µH*
V
W
IN
⎞
⎟ ≅
⎠
OUT
C
IN
10
will require an
L
µ
V
1.375V
= 60mA and
H
C
10µF
CER
OUT
OUT
U
**
3405A1518 F04
V
IN
Figure 5b. LTC3405A-1.375 Small Footprint Efficiency
100mV/DIV
200mA/DIV
200mA/DIV
COUPLED
I
V
LOAD
100
OUT
90
80
70
60
50
40
30
20
10
AC
I
0
L
0.1
V
I
Burst Mode OPERATION
LOAD
IN
= 3.6V
= 100mA TO 300mA
1
LOAD CURRENT (mA)
Figure 5c.
LTC3405A-1.375
20µs/DIV
10
100
V
V
V
IN
IN
IN
3405A1375 F05b
3405A1375 F05c
= 2.7V
= 3.6V
= 4.2V
1000
11
3405a1375f