Texas Instruments TPS5124EVM-001, Руководство пользователя, Страница: 8 / 23

SLUU182 − March 2004
8 High-Performance Dual Synchronous Buck Conversion Using the TPS5124
where
•
V
OUT2
is the allowed overshoot voltage
•
V
OUT1
is the nominal operating voltage
For 6% overshoot, the required capacitance is about 370
µ
F. Four 100-
µ
F, 6.3-V ceramic
capacitors are used. Their ESR value is 2.0 m
Ω
each.
4.4 Input Capacitors
Due to the out of phase operation, the input current ripple is partially cancelled. The total RMS
current in the input capacitor is calculated as follows. This assumes the total input current goes
into the input capacitor to the power ground and ignores the ripple current in the inductor.
UDG−04010
0 V
ǒ
I
OUT1
*
I
AVG
Ǔ
ǒ
I
OUT2
*
I
AVG
Ǔ
I
AVG
0
T
T
2
T
2
)
D2 T
D1 T
I
AVG
Figure 2. Case One (D1 < 0.5, D2 < 0.5)
UDG−04010
ǒ
I
OUT1
*
I
AVG
Ǔ
ǒ
I
OUT1
)
I
OUT2
*
I
AVG
Ǔ
0 T
T
2 T
2
)
D2 T
D1 T
I
AVG
0 V
ǒ
I
OUT2
*
I
AVG
Ǔ
Figure 3. Case Two (D2 < 0.5 < D1 )