Applications Information: continued
4. Connect the ground terminals of the Compensation
7. If DC regulation is to be optimized (at the expense of
degraded transient regulation), adaptive voltage position-
ing can be disabled by connecting to VFB pin directly to the
load with a separate trace (remote sense).
capacitor directly to the ground of the fast feedback filter
capacitor to prevent common mode noise from effecting
the PWM comparator.
5. Place the output filter capacitor(s) as close to the load as
8. Place 5V input capacitors close to the switching MOSFET
possible and connect the ground terminal to pin 14 (LGnd). and synchronous MOSFET.
6. To implement adaptive voltage positioning, connect
both slow and fast feedback pins 16 (VFB) and 8 (VFFB) to
Route gate drive signals VGATE(H) (pin 10) and VGATE(L)
(pin 12 when used) with traces that are a minimum of 0.025
the regulator output right at the inductor terminal. Connect inches wide.
inductor to the output capacitors via a trace with the fol-
lowing resistance:
VCC
To the negative terminal of the
0.1mF
input capacitors
15
11
80mV
IMAX
RTRACE
=
1.0mF
V
COMP
100pF
FFB
This causes the output voltage to be +40mV with no load,
and -40mV with a full load, improving regulator transient
response. This trace must be wide enough to carry the full
output current. (Typical trace is 1.0 inch long, 0.17 inch
wide). Care should be taken to minimize any additional
losses after the feedback connection point to maximize reg-
ulation.
V
8
5
SOFTSTART
OFF TIME
To the negative terminal of the output capacitors
Figure 20: Layout Guidelines
Additional Application Circuits
5V
3.3V
12V
0.1mF
MBRS120
1mF
MBRS120
MBRS
120
1mF
+
100mF/10V x 3
Tantalum
+
1mF
33mF/25V x 3
Tantalum
Si4410DY
Si9410
V
CC2
V
V
GATE(H)
CC1
VCC2
VCC1
VID0
VGATE(H)
3mH
3.3V/10A
5mH
2.5V/7A
V
ID0
V
V
ID1
VID1
VID2
VFB
ID2
CS5155
+
CS5155
100mF/10V x 2
Tantalum
V
ID3
V
ID4
Si9410DY
VID3
VID4
COFF
V
GATE(L)
Si9410
VGATE(L)
C
OFF
PGnd
330pF
330pF
SS
V
FB
SS
PGnd
VFFB
0.1mF
3.3k
COMP
0.1mF
V
3.3k
COMP
FFB
LGnd
LGnd
+
0.33mF
100mF/10V x 3
Tantalum
100pF
0.33mF
100pF
Figure 23: 3.3V to 2.5V/7A converter with 12V bias.
Figure 21: 5V to 3.3V/10A converter.
5V
0.1mF
MBRS120
1mF
MBRS120
MBRS
120
+
100mF/10V x 3
Tantalum
1mF
Remote
Sense
Si4410
V
CC2
V
V
GATE(H)
CC1
3mH
3.3V/10A
V
ID0
V
V
ID1
ID2
V
FB
CS5155
10W
100mF/10V x 3
Tantalum
+
V
V
ID3
Si9410
ID4
V
GATE(L)
C
OFF
330pF
SS
PGnd
3.3k
0.1mF
COMP
V
FFB
LGnd
Connect to
other circuits for
current sharing
0.33mF
100pF
Figure 22: 5V to 3.3V/10A converter with current sharing.
13
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
