LTC3407EMSE Linear Technology, LTC3407EMSE Datasheet - Page 8

• Manufacturer Part Number: LTC3407EMSE
• Description: IC REG DC/DC DUAL 1.5MHZ 10-MSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3407EMSE

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.6 ~ 5 V
• Current - Output: 1A
• Frequency - Switching: 1.5MHz
• Voltage - Input: 2.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP Exposed Pad, 10-HMSOP, 10-eMSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIONS INFORMATION
LTC3407
load currents. This causes a dip in effi ciency in the upper
range of low current operation. In Burst Mode operation,
lower inductance values will cause the burst frequency
to increase.
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 materials are
small and don’t radiate much energy, but generally cost
more than powdered iron core inductors with similar
electrical characteristics. The choice of which style in-
ductor to use often depends more on the price vs size
requirements and any radiated fi eld/EMI requirements
than on what the LTC3407 requires to operate. Table 1
shows some typical surface mount inductors that work
well in LTC3407 applications.
Input Capacitor (C
In continuous mode, the input current of the converter is a
square wave with a duty cycle of approximately V
To prevent large voltage transients, a low equivalent series
resistance (ESR) input capacitor sized for the maximum
RMS current must be used. The maximum RMS capacitor
current is given by:
where the maximum average output current I
the peak current minus half the peak-to-peak ripple cur-
rent, I
This formula has a maximum at V
= I
design because even signifi cant deviations do not offer
much relief. Note that capacitor manufacturer’s ripple cur-
rent ratings are often based on only 2000 hours lifetime.
This makes it advisable to further derate the capacitor,
or choose a capacitor rated at a higher temperature than
required. Several capacitors may also be paralleled to meet
the size or height requirements of the design. An additional
0.1μF to 1μF ceramic capacitor is also recommended on
V
ceramic capacitor solution.
8
IN
I
OUT
RMS
for high frequency decoupling, when not using an all
MAX
/2. This simple worst-case is commonly used to
≈I
MAX
= I
LIM
– ΔI
V
OUT
IN
) Selection
L
/2.
(V
V
IN
IN
– V
OUT
IN
)
= 2V
OUT
, where I
MAX
OUT
equals
/V
RMS
IN
.
Table 1. Representative Surface Mount Inductors
PART
NUMBER
Sumida
CDRH3D16
Sumida
CMD4D06
Panasonic
ELT5KT
Murata
LQH32CN
Output Capacitor (C
The selection of C
minimize voltage ripple and load step transients. Typically,
once the ESR requirement is satisfi ed, the capacitance
is adequate for fi ltering. The output ripple (ΔV
determined by:
where f = operating frequency, C
and ΔI
is highest at maximum input voltage since ΔI
with input voltage. With ΔI
will be less than 100mV at maximum V
with:
Once the ESR requirements for C
RMS current rating generally far exceeds the I
requirement, except for an all ceramic solution.
In surface mount applications, multiple capacitors may
have to be paralleled to meet the capacitance, ESR or RMS
current handling requirement of the application. Aluminum
electrolytic, special polymer, ceramic and dry tantulum
capacitors are all available in surface mount packages. The
OS-CON semiconductor dielectric capacitor available from
Sanyo has the lowest ESR(size) product of any aluminum
electrolytic at a somewhat higher price. Special polymer
ESR
V
OUT
L
COUT
= ripple current in the inductor. The output ripple
VALUE
< 150mΩ
(μH)
1.5
2.2
3.3
4.7
2.2
3.3
4.7
3.3
4.7
1.0
2.2
4.7
I
L
ESR+
OUT
(Ω MAX)
OUT
0.043
0.075
0.110
0.162
0.116
0.174
0.216
0.060
0.097
0.150
DCR
0.17
0.20
is driven by the required ESR to
8f
) Selection
O
L
C
1
= 0.3 • I
CURRENT (A)
OUT
MAX DC
0.950
0.770
0.750
1.55
1.20
1.10
0.90
1.00
0.95
1.00
0.79
0.65
OUT
OUT
= output capacitance
LIM
have been met, the
IN
the output ripple
and f
W × L × H (mm
3.8 × 3.8 × 1.8
3.5 × 4.3 × 0.8
4.5 × 5.4 × 1.2
2.5 × 3.2 × 2.0
L
O
RIPPLE(P-P)
SIZE
increases
= 1.5MHz
OUT
3407fa
) is
3
)