iru3047 International Rectifier Corp., iru3047 Datasheet - Page 12

• Manufacturer Part Number: iru3047
• Description: Dual Synchronous Controller With Current Sharing Circuitry Controller
• Manufacturer: International Rectifier Corp.

IRU3047
From (19), R
Set the zero of compensator to be half of F
compensator capacitor, C
Using equations (20) and (21) we get the following val-
ues for R
12
H(Fo)=g
R
F
Fz =
C
R
C
LC(SLAVE)
2
2
2
2
= 123K; Choose R
= 1023pF; Choose C
=
=
2
g
F
2p 3 R
and C
m
LC(SLAVE)
3R
m
2
=
1
2
3R
can be express as:
2p
S1
1
2
.
S1
2
3
3R
3 Fz
L
1
2p3F
2
3C
2
3
V
IN(SLAVE)
2
OUT
, can be calculated as:
2
2p3Fo3L
O2
= 130K
2
3L
= 1000pF
V
- V
2
IN
3V
---(21)
OUT
- V
OSC
OUT
2
3V
OSC
LC(SLAVE)
=1
---(20)
---(19)
, the
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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
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.
09/09/02
Rev. 1.0