LTC3423EMS#TR Linear Technology, LTC3423EMS#TR Datasheet - Page 8

• Manufacturer Part Number: LTC3423EMS#TR
• Description: IC SYNC BOOST CONV MCRPWR 10MSOP
• Manufacturer: Linear Technology
• Type: Step-Up (Boost)r

Specifications of LTC3423EMS#TR

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.5 ~ 5.5 V
• Current - Output: 1A
• Frequency - Switching: 3MHz
• Voltage - Input: 0.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Power - Output: 750mW
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LTC3423EMSTR

APPLICATIO S I FOR ATIO
Output Capacitor Selection
The output voltage ripple has several components. The
bulk value of the capacitor is set to reduce the ripple due
to charge into the capacitor each cycle. The max ripple due
to charge is given by:
LTC3423/LTC3424
The inductor current ripple is typically set to 20% to 40%
of the maximum inductor current.
For high efficiency, choose an inductor with a high fre-
quency core material, such as ferrite, to reduce core
losses. The inductor should have low ESR (equivalent
series resistance) to reduce the I
able to handle the peak inductor current at full load without
saturating. Molded chokes or chip inductors usually do
not have enough core to support the peak inductor cur-
rents in the 1A to 2A region. To minimize radiated noise,
use a toroid, pot core or shielded bobbin inductor. See
Table 1 for a list of component suppliers.
8
Table 1. Inductor Vendor Information
SUPPLIER
Coilcraft
Coiltronics
Murata
Sumida
Figure 1. Recommended Component Placement. Traces
Carrying High Current Are Direct. Trace Area FB and V
Are Kept Low. Lead Length to Battery Should be Kept Short
VR
Japan: 81-3-3607-5111 81-3-3607-5144
BULK
USA: [phone]
PHONE
[phone]
[phone]
[phone]
[phone]
C
I
OUT
L
•
V
V V
U
OUT
•
IN OUT
V
(
OUT
R
MODE
V
SW
GND
U
FAX
[phone]
[phone]
[phone]
[phone]
t
IN
•
V
–
OUT
SHDN
V
V
V
OUT
IN
DD
V
FB
C
2
)
•
R losses and must be
W
f
Volts
WEBSITE
www.coilcraft.com
www.coiltronics.com
www.murata.com
www.japanlink.com
sumida
3423/24 F01
V
2.7V
TO 5.5V
DD
U
IN
C
Pins
where
The ESR is usually the most dominant factor for ripple in
most power converters. The ripple due to capacitor ESR is
simply given by:
where
Low ESR capacitors should be used to minimize output
voltage ripple. For surface mount applications, AVX TPS
series tantalum capacitors and Sanyo POSCAP or Taiyo-
Yuden ceramic capacitors are recommended. For through-
hole applications Sanyo OS-CON capacitors offer low ESR
in a small package size. See Table 2 for a list of component
suppliers.
In some layouts it may be required to place a 1 F low ESR
capacitor as close to the V
Table 2. Capacitor Vendor Information
SUPPLIER
AVX
Sanyo
Taiyo Yuden [phone]
Input Capacitor Selection
The input filter capacitor reduces peak currents drawn from
the input source and reduces input switching noise. In most
applications a 3.3 F is sufficient.
Output Diode
The Schottky diode across the synchronous PMOS switch
is not required, but provides a lower drop during the break-
before-make time (typically 20ns) of the NMOS to PMOS
transition. The addition of the Schottky diode will improve
peak efficiency (see graph “Efficiency Loss Without
Schottky vs Frequency”). Use of a Schottky diode such as
a MBRM120T3, 1N5817 or equivalent. Since slow recov-
ery times will compromise efficiency, do not use ordinary
rectifier diodes.
I
I
VR
R
L
P
ESR
= Average Inductor Current
= Peak Inductor Current
CESR
= Capacitor Series Resistance
= I
PHONE
[phone]
[phone]
P
• R
ESR
Volts
FAX
[phone]
[phone]
[phone]
OUT
and GND pins as possible.
WEBSITE
www.avxcorp.com
www.sanyovideo.com
www.t-yuden.com
34234f