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DVout + Vout
1–
Vout
Vin
L f
ǒ
1
8 Cout f
) ESR
Ǔ
LAYOUT CONSIDERATIONS
V
I
GND
EN
SW
FB
C1
4.7 µF
L1
10 µH
C2
10 µF
TPS62200
V
I
2.5 V − 6 V
V
O
1.8 V / 300 mA
R1
R2
Cff
TPS62200 , , TPS62201
TPS62202 , TPS62203 , TPS62207
TPS62204 , TPS62205 , TPS62208
SLVS417E – MARCH 2002 – REVISED MAY 2006
At nominal load current the device operates in PWM mode and the overall output voltage ripple is the sum of the
voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging
the output capacitor:
where the highest output voltage ripple occurs at the highest input voltage Vin.
At light load currents, the device operates in power save mode, and the output voltage ripple is independent of
the output capacitor value. The output voltage ripple is set by the internal comparator thresholds. The typical
output voltage ripple is 1% of the output voltage Vo.
Table 2. Recommended Capacitors
CAPACITOR VALUE CASE SIZE COMPONENT SUPPLIER COMMENTS
4.7 µF 0805 Taiyo Yuden JMK212BY475MG Ceramic
10 µF 0805 Taiyo Yuden JMK212BJ106MG Ceramic
TDK C12012X5ROJ106K Ceramic
10 µF 1206 Taiyo Yuden JMK316BJ106KL Ceramic
TDK C3216X5ROJ106M
22 µF 1210 Taiyo Yuden JMK325BJ226MM Ceramic
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 shows stability problems as well as
EMI problems.
Therefore use wide and short traces for the main current paths, as indicated in bold in Figure 17 . The input
capacitor, as well as the inductor and output capacitor, should be placed as close as possible to the IC pins
The feedback resistor network must be routed away from the inductor and switch node to minimize noise and
magnetic interference. To further minimize noise from coupling into the feedback network and feedback pin, the
ground plane or ground traces must be used for shielding. This becomes very important especially at high
switching frequencies of 1 MHz.
Figure 17. Layout Diagram
14
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