Datasheet

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SLVS258A − NOVEMBER 1999 − REVISED DECEMBER 1999
16
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
capacitor selection (continued)
Table 2. Recommended Capicator Values
PART
V
I
I
O
C
i
(µF)
C
(xF)
(µF)
C
o
(µF)
V
PP(TYP)
PART
V
I
(V)
I
O
(mA)
TANTALUM
CERAMIC
(X7R)
(µF)
CERAMIC
(X7R)
TANTALUM
CERAMIC
(X7R)
V
PP(TYP)
(V)
225
10
2.2
22 4.7 90
TPS60130
225 10 2.2
22 60
TPS60130
TPS60131
3.6
33 4.7 120
TPS60131
3.6
300 10 2.2
22 and 10 in
parallel
45
TPS60132
75 4.7 10
TPS60132
TPS60133
3.6
150
4.7 2.2
1
15 22 100
TPS60133
3.6
150
4.7
1
22 90
The TPS6013x devices are charge pumps that regulate the output voltage using pulse-skip regulation mode.
The output voltage ripple is therefore dependent on the values and the ESR of the input, output and flying
capacitors. The only possibility to reduce the output voltage ripple is to choose the appropriate capacitors. The
lowest output voltage ripple can be achieved using ceramic capacitors because of their low ESR and their
frequency characteristic.
Ceramic capacitors typically have an ESR that is more than 10 times lower than tantalum capacitors and they
retain their capacitance at frequencies more than 10 times higher than tantalum. Many different tantalum
capacitors act as an inductance for frequencies higher than 200 kHz. This behavior increases the output voltage
ripple. Therefore the best choice for a minimized ripple is the ceramic capacitor. For applications that do not
need a higher performance in output voltage ripple, tantalum capacitors with a low ESR are a possibility for input
and output capacitor, but a ceramic capacitor should be connected in parallel. Be aware that the ESR of tantalum
capacitors is indirectly proportional to the physical size of the capacitor.
Table 2 is a good starting point for choosing the capacitors. If the output voltage ripple is too high for the
application, it can be improved by selecting the appropriate capacitors. The first step is to increase the
capacitance at the output. If the ripple is still too high, the second step would be to increase the capacitance
at the input.
For the TPS60130 and TPS60131, the smallest board space can be achieved using Sprague’s 595D-series
tantalum capacitors for input and output. However, high capacitance ceramic capacitors will become
competitive in package size soon.
The smallest size for the lower-current devices TPS60132 and TPS60133 can be achieved using the suggested
ceramic capacitors.