ir3084u International Rectifier Corp., ir3084u Datasheet - Page 35

• Manufacturer Part Number: ir3084u
• Description: Xphasetm Vr10, Vr11 & Opteron/athlon64 Control Ic
• Manufacturer: International Rectifier Corp.

Type III Compensation
Determine the compensation at no load, the worst case condition. Choose the crossover frequency fc between
1/10 and 1/5 of the switching frequency per phase. Assume the time constant of the resistor and capacitor across
the output inductors matches that of the inductor, R
where C
Choose resistor R
C
A ceramic capacitor between 10pF and 220pF is usually enough.
CURRENT SHARE LOOP COMPENSATION
The crossover frequency of the current share loop should be at least one decade lower than that of the voltage
loop in order to eliminate the interaction between the two loops. A capacitor from SCOMP to LGND is usually
enough for most of the applications. Choose the crossover frequency of current share loop (f
crossover frequency of voltage loop (f
Where FMI is the PWM gain in the current share loop,
CP1
is optional and may be needed in some applications to reduce the jitter caused by the high frequency noise.
Page 35 of 47
E
C
C
C
R
R
FMI
is equivalent output capacitance.
CP
CP
FB1
FB
SCOMP
=
=
=
=
=
(2π
10
4π
1
2
(V
=
R
FB1
*
*
PWMRMP
*
0.65
O
*
R
−
f
R
f
according to Equation (33), and determine C
FB
C1
L
C
1
V
CP
E
*
)
*
PWMRMP
2
*
R
R
*
*
C
PWMRMP
C
FB1
L
E
PWMRMP
V
E
o
*
−
C
to
V
*
DAC
E
V
C
*
*
I
), and determine the C
V
)
*
f
SW
*
PWMRMP
R
I
(V
FB1
O
*
*
I
V
G
=
−
PWMRMP
V
CS_ROOM
V
2
3
O
DAC
*
*
R
2π
CP and
)
FB
*
*
f
R
CI
C
LE
SCOMP
CP
*
*
1.05
[1
can be determined by Equations (30) and (31),
FB
+
,
*
and R
2π
10
*
6
f
DRP
CI
*
from Equations (32) and (33).
C
E
*
(
V
O
I
O
IR3084U
)]
CI
*
(30)
(31)
(32)
(33)
) based on the
F
(35)
9/14/2005
MI
(34)