SC283 SEMTECH [Semtech Corporation], SC283 Datasheet - Page 16

• Manufacturer Part Number: SC283
• Description: Dual Channel 2.5MHz, 1.8A Synchronous Step-Down Regulator
• Manufacturer: SEMTECH [Semtech Corporation]

© 2010 Semtech Corp.
Applications Information (continued)
To estimate the required input capacitor, determine the
acceptable input ripple voltage and calculate the
minimum value required for C
The input capacitor RMS ripple current varies with the
input and output voltage. The maximum input capacitor
RMS current is found from Equation 7.
The input voltage ripple and RMS current ripple are at
a maximum when the input voltage is twice the output
voltage or 50% duty cycle.
The input capacitor provides a low impedance loop for
the edges of pulsed current drawn by the PMOS switch.
Low ESR/ESL X5R ceramic capacitors are recommended
for this function. To minimise stray inductance ,the
capacitor should be placed as closely as possible to the
VIN and GND pins of the SC283.
I
C
CIN
IN
(
RMS
=

 

)
I
V
∆
=
OUT
V
OUT
V
IN
V
−
V

 

OUT
IN
1
ESR
−

 

V
1
V
OUT

⋅  

−
IN
V
f
V
OSC

 

OUT
IN

 

IN
from Equation 6.
(7)
(6)
16
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SC283