Datasheet
L
1
+
V
OUT
ǒ
V
IN1
* V
OUT
Ǔ
V
IN1
f 0.3 A
(3)
L
2
+
V
in2
ǒ
V
OUT
* V
IN2
Ǔ
V
OUT
f 0.3 A
(4)
I
1
+
I
OUT
0.8
)
V
OUT
ǒ
V
IN1
* V
OUT
Ǔ
2 V
IN1
f L
(5)
I
2
+
V
OUT
I
OUT
0.8 V
IN2
)
V
IN2
ǒ
V
OUT
* V
IN2
Ǔ
2 V
OUT
f L
(6)
CAPACITOR SELECTION
Input Capacitor
Output Capacitor
TPS63000
TPS63001
TPS63002
www.ti.com
........................................................................................................................................................... SLVS520B – MARCH 2006 – REVISED JULY 2008
In both equations f is the minimum switching frequency. In Equation 3 the minimum inductance value, L
1
for step
down mode operation is calculated. V
IN1
is the maximum input voltage. In Equation 4 the minimum inductance,
L
2
, for boost mode operation is calculated. V
IN2
is the minimum input voltage. The recommended minimum
inductor value is either L
1
or L
2
whichever is higher. As an example, a suitable inductor for generating 3.3V from
a Li-Ion battery with a battery voltage range from 2.5V up to 4.2V is 2.2 µ H. The recommended inductor value
range is between 1.5 µ H and 4.7 µ H. 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 5 shows how to calculate the peak current I
1
in step down mode operation and Equation 6 shows how
to calculate the peak current I
2
in boost mode operation.
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 TPS6300x converters:
Table 1. List of Inductors
VENDOR INDUCTOR SERIES
LPS3015
Coilcraft
LPS4012
Murata LQH3NP
Tajo Yuden NR3015
VLF3215
TDK
VLF4012
At least a 4.7 µ F 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.
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 7 can be used.
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