Datasheet

LTC3114-1
22
Rev. C
For more information www.analog.com
APPLICATIONS INFORMATION
the series resistance of the output capacitor and all other
terms as previously defined.
ΔV
P-P(BUCK)
=
I
LOAD
R
ESR
1– t
LOW
f
≅ I
LOAD
R
ESR
Volts
ΔV
P-P(BOOST)
=
I
LOAD
R
ESR
V
OUT
V
IN
1– t
LOW
f
( )
≅ I
LOAD
R
ESR
V
OUT
V
IN
⎛
⎝
⎜
⎞
⎠
⎟
Volts
In most LTC3114-1 applications, an output capacitor
between 10µF and 22µF will work well.
Input Capacitor Selection
The PV
IN
pin carries the full inductor current and provides
power to internal control circuits in the IC. To minimize
input voltage ripple and ensure proper operation of the IC,
a low ESR bypass capacitor with a value of at least 6.8µF
should be located as close to the pin as possible. The
traces connecting this capacitor to PV
IN
and the ground
plane should be made as short as possible. The V
IN
pin
provides power to the LDO regulator and other internal
circuitry. If the PCB trace connecting PV
IN
to V
IN
is long, it
is recommended to add an additional small 0.1µF bypass
capacitor near the V
IN
pin.
When powered through long leads or from a high ESR
power source, a larger value bulk input capacitor may be
required. In such applications, a 47µF to 100µF electrolytic
capacitor in parallel with a 1µF ceramic capacitor generally
yields a high performance, low cost solution.
Recommended Input and Output Capacitors
The capacitors used to filter the input and output of the
LTC3114-1 must have low ESR and must be rated to handle
the large AC currents generated by the switching convert
-
ers. This is important to maintain proper functioning of
the
IC and to reduce output voltage ripple. There are many
capacitor types that are well suited to these applications
including multilayer ceramic, low ESR tantalum, OS-CON
and POSCAP technologies. In addition, there are certain
types of electrolytic capacitors such as solid aluminum
organic polymer capacitors that are designed for low ESR
and high AC currents and these are also well suited to
some LTC3114-1 applications. Table2 provides a partial
listing of appropriate capacitors to use with the LTC3114-1.
The choice of capacitor technology is primarily dictated
by a trade-off between size, leakage current and cost. In
backup power applications, the input or output capacitor
might be a super or ultra capacitor with a capacitance value
measuring in the Farad range. The selection criteria in these
Table2. Representative Bypass and Output Capacitors
MANUFACTURER,
PART NUMBER
V
ALUE
(µF)
VOLTAGE
(V)
SIZE L × W × H (mm),
TYPE, ESR
AVX
12103D226MAT2A 22 25 3.2 × 2.5 × 2.79
X5R Ceramic
TP
ME226K050R0075 22 50 7.3 × 4.3 × 4.1
Tantalum, 75mΩ
Kemet
C2220
X226K3RACTU 22 25 5.7 × 5.0 × 2.4
X7R Ceramic
A700D226M016
ATE030 22 16 7.3 × 4.3 × 2.8
Alum. Polymer, 30mΩ
Murata
G
RM32ER71E226KE15L 22 25 3.2 × 2.5 × 2.5
X7R Ceramic
Nichicon
PL
V1E121MDL1 82 25 8 × 8 × 12
Alum. Polymer, 25mΩ
Panasonic
ECJ-4Y
B1E226M 22 25 3.2 × 2.5 × 2.5
X5R Ceramic
Sanyo
25T
QC22MV 22 25 7.3 × 4.3 × 3.1
POSCAP, 50mΩ
16T
QC100M 100 16 7.3 × 4.3 × 1.9
POSCAP, 45mΩ
25SV
PF47M 47 25 6.6 × 6.6 × 5.9
OS-CON, 30mΩ
T
aiyo Yuden
UMK325BJ106MM-T 10 50 3.2 × 2.5 × 2.5
X5R Ceramic
TM
K325BJ226MM-T 22 25 3.2 × 2.5 × 2.5
X5R Ceramic
TDK
KT
J500B226M55BFT00 22 50 6.0 × 5.3 × 5.5
X7R Ceramic
C5750
X7R1H106M 10 50 5.7 × 5.0 × 2.0
X7R Ceramic
CK
G57NX5R1E476M 47 25 6.5 × 5.5 × 5.5
X5R Ceramic
Vishay
94SV
PD476X0035F12 47 35 10.3 × 10.3 × 12.6
OS-CON, 30mΩ
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