MP2317 – 26V, 1A, SYNCHRONOUS, STEP-DOWN CONVERTER
MP2317 Rev. 1.0 www.MonolithicPower.com 13
3/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2016 MPS. All Rights Reserved.
For ceramic capacitors, the impedance at the
switching frequency is dominated by the
capacitance, which mainly causes the output
voltage ripple. For simplification, the output
voltage ripple can be estimated with Equation
(8):
OUT OUT
OUT
2
IN
S1
VV
V1
V
8f L C2
(8)
In the case of tantalum or electrolytic capacitors,
the ESR dominates the impedance at the
switching frequency. For simplification, the
output ripple can be approximated with
Equation (9):
OUT OUT
OUT ESR
IN
S1
VV
V1R
fL V
9)
The characteristics of the output capacitor also
affect the stability of the regulation system. The
MP2317 can be optimized for a wide range of
capacitance and ESR values.
External Bootstrap Diode
An optional, external diode may enhance the
efficiency of the regulator. The conditions of the
external diode are applied when the output
voltage is 5V.
In this case, it is recommended to connect an
external BST diode from V
OUT
to BST (see
Figure 4).
Figure 4: Optional External Bootstrap Diode
Added to Enhance Efficiency
External VCC Diode
When V
OUT
is 5V, an external optional diode
from V
OUT
to VCC may enhance the efficiency
of the regulator (see Figure 5).
C4
0.1µF
1N4148
Figure 5: Optional External Diode Added to
Enhance Efficiency
