Datasheet

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SGLS243A − APRIL 2004 − REVISED JUNE 2008
14
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
adjustable output voltage version
When the adjustable output voltage version (TPS62000) is used, the output voltage is set by the external resistor
divider (see Figure 15).
The output voltage is calculated as:
V
O
+ 0.45 V
ǒ
1 )
R1
R2
Ǔ
With R1 + R2 ≤ 1 MΩ
R1 + R2 should not be greater than 1 MΩ because of stability reasons.
For stability reasons, a small bypass capacitor (C
ff
) is required in parallel to the upper feedback resistor, see
Figure 15. The bypass capacitor value can be calculated as:
C
(ff)
+
1
2π x 30000 x R1
for C
o
t 47 µF
C
(ff)
+
1
2π x 5000 x R1
for C
o
≥ 47 µF
R1 is the upper resistor of the voltage divider. For C
(ff)
, choose a value which comes closest to the computed
result.
V
IN
1
8
6
7
32
9
5
10
4
L1 = 10 µH
EN
ILIM
SYNC
GND FC
PG
PGND
FB
L
TPS62000
+
C
o
= 10 µF
V
O
= 2.5 V/600 mA
C3 = 0.1 µF
C
i
= 10 µF
V
I
= 2.7 V to 5.5 V
R3 = 320 kΩ
R1 = 820 kΩ
C
(ff)
=
6.8 pF
R2 = 180 kΩ
+
PG
Figure 15. Typical Application Circuit for Adjustable Output Voltage Option
inductor selection
A 10 µH minimum output inductor is used with the TPS6200x. Values larger than 22 µH or smaller than 10 µH
may cause stability problems because of the internal compensation of the regulator.
For output voltages greater than 1.8 V, a 22-µH inductance might be used in order to improve the efficiency of
the converter.
After choosing the inductor value of typically 10 µH, two additional inductor parameters should be considered:
first the current rating of the inductor and second the dc resistance.
The dc resistance of the inductance influences directly the efficiency of the converter. Therefore, an inductor
with the lowest dc resistance should be selected for the highest efficiency.