Datasheet

I
1
+
I
OUT
0.8
)
V
OUT
ǒ
V
IN1
* V
OUT
Ǔ
2 V
IN1
f L
I
2
+
V
OUT
I
OUT
0.8 V
IN2
)
V
IN2
ǒ
V
OUT
* V
IN2
Ǔ
2 V
OUT
f L
C
OUT
+ 5 L
mF
mH
TPS63030
TPS63031
SLVS696B –OCTOBER 2008–REVISED MARCH 2012 www.ti.com
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.
(4)
(5)
In both equations f is the minimum switching frequency. V
IN2
is the minimum input voltage. 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 TPS6303x converters:
Table 2. List of Inductors
VENDOR INDUCTOR SERIES
LPS3015
Coilcraft
EPL3010
Murata LQH3NP
Tajo Yuden NR3015
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.
Bypass Capacitor
To make sure that the internal control circuits are supplied with a stable low noise supply voltage, a capacitor can
be connected between VINA and GND. Using a ceramic capacitor with a value of 0.1μF is recommended. The
value of this capacitor should not be higher than 0.22μF.
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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