Datasheet

C
OUT
+ 5 L
mF
mH
I
2
+
V
OUT
I
OUT
0.8 V
IN2
)
V
IN2
ǒ
V
OUT
* V
IN2
Ǔ
2 V
OUT
f L
I
1
+
I
OUT
0.8
)
V
OUT
ǒ
V
IN1
* V
OUT
Ǔ
2 V
IN1
f L
TPS63010
TPS63011
TPS63012
SLVS653B –JUNE 2008–REVISED MAY 2012 www.ti.com
In Equation 2 the minimum inductance value, L
1
for step down mode operation is calculated. V
IN1
is the
maximum input voltage. In Equation 3 the minimum inductance, L
2
, for boost mode operation is calculated. The
recommended minimum inductor value is either L
1
or L
2
whichever is higher. As an example, a suitable inductor
for generating 3.3 V from a Li-Ion battery with a battery voltage range from 2.5 V up to 4.2 V is 2.2 μH. The
recommended inductor value range is between 1 μH and 4.7 μH. In general, this means that at high voltage
conversion rates, higher inductor values offer better performance.
With the chosen inductance value, the peak current for the inductor in steady state operation can be calculated.
Equation 4 shows how to calculate the peak current I
1
in step down mode operation and Equation 5 shows how
to calculate the peak current I
2
in boost mode operation. V
IN2
is the minimum input voltage.
(4)
(5)
The critical current value for selecting the right inductor is the higher value of I
1
and I
2
. It also needs to be taken
into account that load transients and error conditions may cause higher inductor currents. This also needs to be
taken into account when selecting an appropriate inductor. The following inductor series from different suppliers
have been used with TPS6301x converters:
Table 3. List of Inductors
VENDOR INDUCTOR SERIES
LPS3015
Coilcraft
LPS4012
FDK MIPSA2520
LQH3NP
Murata
LQM2HP
Toko FDSE0312
CAPACITOR SELECTION
Input Capacitor
At least a 4.7-μF input capacitor 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 PGND
pins of the IC is recommended.
Output Capacitor
For the output capacitor, it is recommended to use small ceramic capacitors placed as close as possible to the
VOUT and PGND pins of the IC. If, for any reason, the application requires the use of large capacitors which can
not be placed close to the IC, using a smaller ceramic capacitor in parallel to the large one is recommended.
This small capacitor should be placed as close as possible to the VOUT and PGND pins of the IC.
To get an estimate of the recommended minimum output capacitance, Equation 6 can be used.
(6)
A capacitor with a value in the range of the calculated minimum should be used. This is required to maintain
control loop stability. There are no additional requirements regarding minimum ESR. There is also no upper limit
for the output capacitance value. Larger capacitors will cause lower output voltage ripple as well as lower output
voltage drop during load transients.
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