mp1543dj MPS, mp1543dj Datasheet - Page 7

• Manufacturer Part Number: mp1543dj
• Description: 1.5a, 500khz Synchronous Rectified Step-up Converter
• Manufacturer: MPS

Selecting the Feed-Forward Capacitor
A feed-forward capacitor C3 in parallel with the
high-side resistor R1 can be added to improve
the output ripple at discontinuous conduction
mode and the load transient response (see
Figure 2). Up to 220pF for this capacitor is
recommended for 3.3V output applications.
Selecting the Schottky Diode
A Schottky diode D1 in parallel with the high-
side P-Channel MOSFET is necessary to clamp
the SW node to a safe level for outputs of 4V or
above. A 0.5A, 20V Schottky diode can be used
for this purpose. See Figure 3.
MP1543 Rev. 1.0
1/11/2006
Figure 3—5V Typical Application Circuit with External Schottky Diode and Output Disconnect
TM
Figure 2—3.3V Typical Application Circuit with Feed-Forward Capacitor
1.8V - 3.2V
MP1543 — 1.5A, 500KHZ SYNCHRONOUS RECTIFIED STEP-UP CONVERTER
V
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
EN
2.5V - 4.2V
IN
V
EN
IN
5
EN
5
EN
MP1543
© 2006 MPS. All Rights Reserved.
GND
SW
www.MonolithicPower.com
4
2
MP1543
Not Required
GND
SW
OUT
4
2
FB
3
1
OUT
FB
D1
LAYOUT CONSIDERATIONS
High frequency switching regulators require
very careful layout for stable operation and low
noise. All components must be placed as close
to the IC as possible. All feedback components
must be kept close to the FB pin to prevent
noise injection on the FB pin trace. The ground
return of C1 and C2 should be tied close to the
GND pin. See the MP1543 demo board layout
for reference.
3
1
C3
Up to 220pF
OPTIONAL
MP1543_F02
V
5V
400mA
OUT
MP1543_F02
V
3.3V
400mA
OUT
7