MP2115 – 2A, 6V SYNCHRONOUS STEP-DOWN CONVERTER
MP2115 Rev. 1.0 www.MonolithicPower.com 10
2/28/2011 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
Input Capacitor Selection
The input capacitor (C1) reduces the surge
current drawn from the input and switching
noise from the device. The input capacitor
impedance at the switching frequency must be
less than input source impedance to prevent
high frequency switching current passing to the
input. Ceramic capacitors with X5R or X7R
dielectrics are highly recommended because of
their low ESR and small temperature
coefficients. For most applications, a 10µF
capacitor is sufficient.
VSYS Capacitor Selection
The VSYS capacitor C2 is used to supply the
USB port and with the peak output current,
such as during the TDM frame. That output
peak current is about 2A. Use three 470µF
capacitors to avoid large voltage drops.
Output Capacitor Selection
The output capacitor (C4) keeps output voltage
ripple small and ensures regulation loop stable.
The output capacitor impedance should remain
low at the switching frequency. Ceramic
capacitors with X5R or X7R dielectrics are
recommended. The output ripple ∆
VOUT
is
approximately:
)
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
××
+×
××
−×
≤∆
2Cf8
1
ESR
LfV
VVV
V
OSCOSCIN
OUTINOUT
OUT
