LTC3406B-2ES5#TRM Linear Technology, LTC3406B-2ES5#TRM Datasheet - Page 8

• Manufacturer Part Number: LTC3406B-2ES5#TRM
• Description: IC SYNC BUCK REG 600MA TSOT23-5
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3406B-2ES5#TRM

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 5.5 V
• Current - Output: 600mA
• Frequency - Switching: 2.25MHz
• Voltage - Input: 2.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-5, TSOT-5, TSOP-5
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Other names: LTC3406B-2ES5; LTC3406B-2ES5

LTC3406B-2
APPLICATIO S I FOR ATIO
The basic LTC3406B-2 application circuit is shown in
Figure 1. External component selection is driven by the
load requirement and begins with the selection of L fol-
lowed by C
Inductor Selection
For most applications, the value of the inductor will fall in
the range of 1µH to 4.7µH. Its value is chosen based on the
desired ripple current. Large value inductors lower ripple
current and small value inductors result in higher ripple
currents. Higher V
current as shown in equation 1. A reasonable starting point
for setting ripple current is ∆I
The DC current rating of the inductor should be at least
equal to the maximum load current plus half the ripple
current to prevent core saturation. Thus, a 720mA rated
inductor should be enough for most applications (600mA
+ 120mA). For better efficiency, choose a low DC-resis-
tance inductor.
Inductor Core Selection
Different core materials and shapes will change the size/
current and price/current relationship of an inductor.
Toroid or shielded pot cores in ferrite or permalloy mate-
rials are small and don’t radiate much energy, but gener-
ally cost more than powdered iron core inductors with
similar electrical characteristics. The choice of which style
inductor to use often depends more on the price vs size
requirements and any radiated field/EMI requirements
than on what the LTC3406B-2 requires to operate. Table 1
shows some typical surface mount inductors that work
well in LTC3406B-2 applications.
C
In continuous mode, the source current of the top MOSFET
is a square wave of duty cycle V
voltage transients, a low ESR input capacitor sized for the
maximum RMS current must be used. The maximum
RMS capacitor current is given by:
8
IN
C
∆ =
and C
IN
I
L
required I
( )( )
OUT
f L
IN
1
and C
Selection
V
OUT
RMS
OUT
IN
U
⎛
⎜
⎝
or V
1
≅
.
−
I
OMAX
U
V
OUT
V
OUT
IN
L
= 240mA (40% of 600mA).
[
also increases the ripple
⎞
⎟
⎠
OUT
V
OUT
W
/V
(
IN
V
. To prevent large
IN
V
−
IN
V
OUT
U
)
]
1 2 /
(1)
Table 1. Representative Surface Mount Inductors
Part
Number
Sumida
CDRH2D11
Sumida
CDRH2D18/LD
Sumida
CMD4D06
Murata
LQH32C
Taiyo Yuden
LQLBC2518
Toko
D412F
This formula has a maximum at V
I
monly used for design because even significant deviations
do not offer much relief. Note that the capacitor
manufacturer’s ripple current ratings are often based on
2000 hours of life. This makes it advisable to further derate
the capacitor, or choose a capacitor rated at a higher
temperature than required. Always consult the manufac-
turer if there is any question.
The selection of C
series resistance (ESR).
Typically, once the ESR requirement for C
met, the RMS current rating generally far exceeds the
I
mined by:
where f = operating frequency, C
and ∆I
voltage, the output ripple is highest at maximum input
voltage since ∆I
RMS
RIPPLE(P-P)
∆
V
= I
OUT
L
OUT
= ripple current in the inductor. For a fixed output
≅ ∆
/2. This simple worst-case condition is com-
requirement. The output ripple ∆V
I ESR
Value
L
(µH)
1.5
2.2
3.3
2.2
3.3
4.7
2.2
3.3
4.7
1.0
2.2
4.7
1.0
1.5
2.2
2.2
3.3
4.7
L
⎛
⎜
⎝
increases with input voltage.
OUT
+
is driven by the required effective
(ΩMAX)
0.068
0.123
0.041
0.054
0.078
0.116
0.216
0.060
0.150
0.080
0.110
0.130
0.098
0.174
0.097
DCR
0.14
0.20
0.22
8
fC
1
OUT
OUT
⎞
⎟
⎠
Current (A)
MAX DC
0.90
0.78
0.60
0.85
0.75
0.63
0.95
0.77
0.75
1.00
0.79
0.65
0.78
0.66
0.60
1.14
0.90
0.80
= output capacitance
IN
= 2V
OUT
WxLxH (mm
3.2 x 3.2 x 1.2
3.2 x 3.2 x 2.0
3.5 x 4.1 x 0.8
2.5 x 3.2 x 2.0
1.8 x 2.5 x 1.8
4.6 x 4.6 x 1.2
OUT
sn3406b2 3406b2fs
OUT
has been
Size
, where
is deter-
3
)