ir3500v International Rectifier Corp., ir3500v Datasheet - Page 28

• Manufacturer Part Number: ir3500v
• Description: Xphase3 Vr11.1 Cpu Vtt Control Ic
• Manufacturer: International Rectifier Corp.

For applications where AVP is not required, the compensation is the same as for the regular voltage mode
control. For converters using Polymer, AL-Polymer, and ceramic capacitors, which have much higher ESR zero
frequency, type III compensation is required as shown in Figure 22(b) with R
Type II Compensation for AVP Applications
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, and determine R
C
respectively.
C
A ceramic capacitor between 10pF and 220pF is usually enough.
Type III Compensation for AVP Applications
Determine the compensation at no load, the worst case condition. Assume the time constant of the resistor and
capacitor across the output inductors matches that of the inductor, the crossover frequency and phase margin of
the voltage loop can be estimated by (24) and (25), where R
Choose the desired crossover frequency fc around fc1 estimated by (24) or choose fc between 1/10 and 1/5 of
the switching frequency per phase, and select the components to ensure the slope of close loop gain is -20dB
per decade around the crossover frequency. Choose resistor R
C
R
frequency and transient load response. Determine R
E
CP1
DRP
CP
are the equivalent inductance of output inductors and the equivalent capacitance of output capacitors
and C
is optional and may be needed in some applications to reduce the jitter caused by the high frequency noise.
from (27) and (28).
Page 28 of 34
CP
have limited effect on the crossover frequency, and are used only to fine tune the crossover
θ
C
C
C
R
R
R
f
C
CP
C
CP
CP
FB
FB
DRP
1
1
1
=
=
=
=
=
=
=
2
=
2 (
4
2 (
10
90
V
π
1
2
π
(
I
π
π
*
R
R
*
∗
∗
−
∗
C
∗
FB
FB
f
R
E
A
C
f
1
f
L
1
C
C
CP
+
∗
+
E
∗
)
tan(
)
R
G
2
R
2
2 (
R
R
∗
DRP
∗
CS
∗
FB
DRP
FB
π
C
L
L
. 0
to
1
E
1
V
*
*
E
E
)
I
R
) 5
∗
∗
∗
f
C
FB
C
C
C
*
∗
E
E
FB
∗
C
180
∗
R
∗
R
π
*
R
FB
R
LE
R
FB
FB
1
C
=
)
∗
∗
2
5
5
2
3
R
CP
FB
and C
LE
CP
is the equivalent resistance of inductor DCR.
from (29) and (30).
FB1
CP
according to (26), and determine C
and C
DRP
CP
from (23) and (23), where L
and C
DRP
removed.
(22)
(23)
(24)
(25)
(26)
(27)
(28)
(29)
July 03, 2008
IR3500V
FB
E
and
and