Datasheet

TPS60120, TPS60121, TPS60122, TPS60123, TPS60124, TPS60125
REGULATED 200-mA HIGH EFFICIENCY CHARGE PUMP
DC/DC CONVERTERS
SLVS257B – NOVEMBER 1999 – REVISED AUGUST 2000
16
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
–0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
–0.2 –0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
t – Time (Start-Up Timing – ms
V
O
– V
V
I
= 2.4 V
R
LOAD
= 16.5 Ω
ENABLE – V
V
O
– Output Voltage and Enable Signal – V
TPS60120
OUTPUT VOLTAGE
vs
TIME
(START-UP TIMING)
Figure 26
APPLICATION INFORMATION
capacitor selection
The TPS6012x charge pumps require only four external capacitors as shown in the basic application circuit.
Their values and types are closely linked to the output current and output noise/ripple requirements. For lowest
noise and ripple, low ESR (<0.1 Ω) capacitors should be used for input and output capacitors.
The input capacitor improves system efficiency by reducing the input impedance. It also stabilizes the input
current of the power source. The input capacitor should be chosen according to the power supply used and the
distance from the power source to the converter IC. The input capacitor also has an impact on the output ripple
requirements. The lower the ESR of the input capacitor C
i
, the lower is the output ripple. C
i
is recommended
to be about two to four times as large as C
(xF)
.
The output capacitor (C
O
) can be selected from 5-times to 50-times larger than C
(xF)
, depending on the ripple
tolerance. The larger C
O
and the lower its ESR, the lower will be the output voltage ripple. C
i
and C
O
can be
either ceramic or low-ESR tantalum; aluminum capacitors are not recommended.