Datasheet

³ ´
2
L
C
2
´
> ´
OUT OUT
IN
V I
0.8 100 mA
V
´
ì
ï
´
í
ï
î
OUT OUT
IN
L,MAX
V I
+ 100 mA; continous current operation
0.8 V
I =
200 mA; discontinuous current operation
TPS61220, TPS61221, TPS61222
SLVS776A –JANUARY 2009–REVISED APRIL 2014 www.ti.com
Typical Applications (continued)
(2)
Equation 2 provides a suitable inductor current rating. However, remember that load transients and error
conditions may cause higher inductor currents.
Equation 3 provides an easy way to estimate whether the device will work in continuous or discontinuous
operation depending on the operating points. As long as the Equation 3 is true, continuous operation is typically
established. If Equation 3 becomes false, discontinous operation is typically established.
(3)
The following inductor series from different suppliers have been used with TPS6122x converters:
Table 2. List Of Inductors
VENDOR INDUCTOR SERIES
EPL3015
Coilcraft
EPL2010
Murata LQH3NP
Tajo Yuden NR3015
Wurth Elektronik WE-TPC Typ S
10.2.1.2.4 Capacitor Selection
10.2.1.2.4.1 Input Capacitor
An input capacitor value of at least 10 μF is recommended to improve transient behavior of the regulator and
EMI behavior of the total power supply circuit. A ceramic capacitor placed as close as possible to the VIN and
GND pins of the IC is recommended.
10.2.1.2.4.2 Output Capacitor
For the output capacitor C
2
, small ceramic capacitors are recommended, placed as close as possible to the
VOUT and GND pins of the IC. If, for any reason, the application requires the use of large capacitors which
cannot be placed close to the IC, the use of a small ceramic capacitor with a capacitance value of around 2.2μF
in parallel to the large one is recommended. This small capacitor should be placed as close as possible to the
VOUT and GND pins of the IC.
A minimum capacitance value of 4.7 μF should be used, 10 μF is recommended. If the inductor value exceeds
4.7 μH, the value of the output capacitance value needs to be half the inductance value or higher for stability
reasons, see Equation 4.
(4)
The TPS6122x is not sensitive to the ESR in terms of stability. However, low ESR capacitors, such as ceramic
capacitors, are recommended anyway to minimize output voltage ripple. If heavy load changes are expected,
increase the output capacitor value to avoid output voltage drops during fast load transients.
10.2.1.3 Application Curves
Figure 25 shows the excelent efficiency of the converter, which remains above 80% even with heavily discharged
cells.
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