TPS61040
TPS61041
SLVS413 – FEBRUARY 2002
APPLICATION INFORMATION
Table 2. Recommended Input and Output Capacitors
DEVICE
CAPACITOR
VOLTAGE RATING
COMPONENT SUPPLIER
Tayo Yuden JMK212BY475MG
Tayo Yuden JMK212BJ106MG
Tayo Yuden TMK316BJ105KL
Tayo Yuden GMK316BJ105KL
Tayo Yuden TMK325BJ475MG
COMMENTS
4.7 µF/X5R/0805
10 µF/X5R/0805
1.0 µF/X7R/1206
1.0 µF/X5R/1206
4.7 µF/X5R/1210
6.3 V
6.3 V
25 V
35 V
25 V
C
C
C
C
C
/C
IN OUT
/C
IN OUT
TPS61040/41
OUT
OUT
OUT
input capacitor selection
For good input voltage filtering, low ESR ceramic capacitors are recommended. A 4.7 µF ceramic input
capacitor is sufficient for most of the applications. For better input voltage filtering this value can be increased.
Refer to Table 2 and typical applications for input capacitor recommendations.
diode selection
ToachievehighefficiencyaSchottkydiodeshouldbeused. Thecurrentratingofthediodeshouldmeetthepeak
current rating of the converter as it is calculated in the section peak current control. Use the maximum value
for I
for this calculation. Refer to Table 3 and the typical applications for the selection of the Schottky diode.
LIM
Table 3. Recommended Schottky Diode for Typical LCD Bias Supply (see Figure 15)
DEVICE
REVERSE VOLTAGE
COMPONENT SUPPLIER
ON Semiconductor MBR0530
ON Semiconductor MBR0520
COMMENTS
30 V
20 V
20 V
30 V
TPS61040/41
ON Semiconductor MBRM120L High efficiency
Toshiba CRS02
layout considerations
Typical for all switching power supplies, the layout is an important step in the design; especially at high peak
currents and switching frequencies. If the layout is not carefully done, the regulator might show noise problems
and duty cycle jitter.
The input capacitor should be placed as close as possible to the input pin for good input voltage viltering. The
inductor and diode should be placed as close as possible to the switch pin to minimize the noise coupling into
other circuits. Since the feedback pin and network is a high impedance circit the feedback network should be
routed away from the inductor. The feedback pin and feedback network should be shielded with a ground plane
or trace to minimize noise coupling into this circuit.
Wide traces should be used for connections in bold as shown in Figure 15. A star ground connection or ground
plane minimizes ground shifts and noise.
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