LTC3411EDD Linear Technology, LTC3411EDD Datasheet - Page 10

• Manufacturer Part Number: LTC3411EDD
• Description: IC DC/DC CONV STEP-DOWN 10DFN
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3411EDD

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.8 ~ 5 V
• Current - Output: 1.25A
• Frequency - Switching: 1MHz
• Voltage - Input: 2.63 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-DFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIONS INFORMATION
LTC3411
higher ripple current which causes this to occur at lower
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 induc-
tor. 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 inductor to use often depends more on the price vs
size requirements and any radiated fi eld/EMI requirements
than on what the LTC3411 requires to operate. Table 1
shows some typical surface mount inductors that work
well in LTC3411 applications.
Table 1. Representative Surface Mount Inductors
MANU-
FACTURER PART NUMBER
Toko
Toko
Coilcraft
Coilcraft
Sumida
Sumida
Taiyo Yuden N06DB2R2M
Taiyo Yuden N05DB2R2M
Murata
10
A914BYW-2R2M-D52LC 2.2μH
A915AY-2ROM-D53LC
D01608C-222
LP01704-222M
CDRH4D282R2
CDC5D232R2
LQN6C2R2M04
VALUE
2.2μH
2.2μH
2.2μH
2.2μH
2.2μH
2.2μH
2.2μH
2μH
CURRENT DCR HEIGHT
MAX DC
2.05A
2.04A
2.16A
3.3A
2.3A
2.4A
3.2A
2.9A
3.2A
120mΩ 1mm
49mΩ
22mΩ
70mΩ
23mΩ
30mΩ 2.5mm
29mΩ 3.2mm
32mΩ 2.8mm
24mΩ
2mm
3mm
3mm
3mm
5mm
Catch Diode Selection
Although unnecessary in most applications, a small
improvement in effi ciency can be obtained in a few ap-
plications by including the optional diode D1 shown in
Figure 5, which conducts when the synchronous switch is
off. When using Burst Mode operation or pulse skip mode,
the synchronous switch is turned off at a low current and
the remaining current will be carried by the optional diode.
It is important to adequately specify the diode peak cur-
rent and average power dissipation so as not to exceed
the diode ratings. The main problem with Schottky diodes
is that their parasitic capacitance reduces the effi ciency,
usually negating the possible benefi ts for LTC3411 circuits.
Another problem that a Schottky diode can introduce is
higher leakage current at high temperatures, which could
reduce the low current effi ciency.
Remember to keep lead lengths short and observe proper
grounding (see Board Layout Considerations) to avoid ring-
ing and increased dissipation when using a catch diode.
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:
I
RMS
≈
I
MAX
V
IN
OUT IN
) Selection
(
V
V
IN
−
V
OUT
)
OUT
/V
3411fb
IN
.