LTC3114-1_15 Datasheet, PDF (21/34 Pages) Linear Technology – 40V, 1A Synchronous Buck-Boost DC/DC Converter with Programmable Output Current

LTC3114-1
APPLICATIONS INFORMATION
the series resistance of the output capacitor and all other
terms as previously defined.
∆V_{P-P(BUCK )}
=
I_LOADR_ESR
1– t_LOW f
≅ I_LOADR_ESR
Volts
( ) ^{∆VP-P(BOOST}
)
=
I_LOADR_ESRV_OUT
V_IN 1– t_LOW f
≅
I_LOADR_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.
Table 2. Representative Bypass and Output Capacitors
MANUFACTURER,
PART NUMBER
VALUE VOLTAGE SIZE L × W × H (mm),
(µF)
(V)
TYPE, ESR
AVX
12103D226MAT2A
22
25
3.2 × 2.5 × 2.79
X5R Ceramic
TPME226K050R0075
22
50
7.3 × 4.3 × 4.1
Tantalum, 75mΩ
Kemet
C2220X226K3RACTU
22
25
5.7 × 5.0 × 2.4
X7R Ceramic
A700D226M016ATE030 22
16
7.3 × 4.3 × 2.8
Alum. Polymer, 30mΩ
Murata
GRM32ER71E226KE15L 22
25
3.2 × 2.5 × 2.5
X7R Ceramic
Nichicon
PLV1E121MDL1
82
25
8 × 8 × 12
Alum. Polymer, 25mΩ
Panasonic
ECJ-4YB1E226M
22
25
3.2 × 2.5 × 2.5
X5R Ceramic
Sanyo
25TQC22MV
22
25
7.3 × 4.3 × 3.1
POSCAP, 50mΩ
16TQC100M
100
16
7.3 × 4.3 × 1.9
POSCAP, 45mΩ
25SVPF47M
47
25
6.6 × 6.6 × 5.9
OS-CON, 30mΩ
Taiyo Yuden
UMK325BJ106MM-T
10
50
3.2 × 2.5 × 2.5
X5R Ceramic
TMK325BJ226MM-T
22
25
3.2 × 2.5 × 2.5
X5R Ceramic
TDK
KTJ500B226M55BFT00 22
50
6.0 × 5.3 × 5.5
X7R Ceramic
C5750X7R1H106M
10
50
5.7 × 5.0 × 2.0
X7R Ceramic
CKG57NX5R1E476M
47
25
6.5 × 5.5 × 5.5
X5R Ceramic
Vishay
94SVPD476X0035F12 47
35
10.3 × 10.3 × 12.6
OS-CON, 30mΩ
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
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