iru3048 International Rectifier Corp., iru3048 Datasheet - Page 11

• Manufacturer Part Number: iru3048
• Description: Dual Synchronous Pwm Controller Circuitry And Ldo Controller
• Manufacturer: International Rectifier Corp.

Layout Consideration
The layout is very important when designing high fre-
quency switching converters. Layout will affect noise
pickup and can cause a good design to perform with
less than expected results.
Start to place the power components, make all the con-
nection in the top layer with wide, copper filled areas.
The inductor, output capacitor and the MOSFET should
be close to each other as possible. This helps to reduce
the EMI radiated by the power traces due to the high
switching currents through them. Place input capacitor
TYPICAL APPLICATION
12V to 3.3V @ 4A
12V to 1.8V @ 4A
3.3V to 2.5V @ 2A
Rev. 1.7
09/12/02
2.5V @ 2A
3.3V
12V
47uF
C14
1uF
C9
1800pF
3900pF
C19
C18
IRLR2703
C15
47uF
C8
1uF
Figure 8 - Typical application of IRU3048 in an on-board DC-DC converter
Q1
R5
1K
1uF
10
16.2K
R2
43.2K
C1
R 1 1
C24
0.1uF
R9
V
R7
1K
V
Comp1
Vcc
Fb3
Comp2
SS
OUT3
using a single 12V supply for switcher.
IRU3048
VcH1
Gnd
U1
VcH2
HDrv2
HDrv1
LDrv2
LDrv1
PGnd
Fb1
Fb2
www.irf.com
33uF
C2
directly to the drain of the high-side MOSFET, to reduce
the ESR replace the single input capacitor with two par-
allel units. The feedback part of the system should be
kept away from the inductor and other noise sources,
and be placed close to the IC. In multilayer PCB use
one layer as power ground plane and have a control cir-
cuit ground (analog ground), to which all signals are ref-
erenced. The goal is to localize the high current path to
a separate loop that does not interfere with the more
sensitive analog control function. These two grounds
must be connected together on the PC board layout at a
single point.
1/2 of Q3
IRF7313
1/2 of Q3
IRF7313
1/2 of Q2
IRF7313
1/2 of Q2
IRF7313
L1
1uH
C6
47uF
C16
47uF
R4
4.7
R13
4.7
C20
470pF
C10
470pF
V
V
6.8uH
10uH
C7
1uF
C17
1uF
D1
BAT54S
L3
L4
R6
1.65K
R8
1K
R14
442
R15
1K
C21, C22
2x 150uF
C11, C12
2x 150uF
V
C3
0.1uF
IRU3048
C23
1uF
C13
1uF
3.3V @ 4A
1.8V @ 4A
11