ISL6219 Intersil Corporation, ISL6219 Datasheet - Page 14

• Manufacturer Part Number: ISL6219
• Description: Microprocessor CORE Voltage Regulator Precision Multi-Phase BUCK PWM Controller for Mobile Applications
• Manufacturer: Intersil Corporation

defined below, there is a separate set of equations for the
compensation components.
In Equations 17, L is the per-channel filter inductance
divided by the number of active channels; C is the sum total
of all output capacitors; ESR is the equivalent-series
resistance of the bulk output-filter capacitance; and V
the peak-to-peak sawtooth signal amplitude as described in
Figure 5 and Electrical Specifications.
Once selected, the compensation values in Equations 17
assure a stable converter with reasonable transient perfor-
mance. In most cases, transient performance can be
improved by making adjustments to R
value of R
oscilloscope until no further improvement is noted. Normally,
Case 1:
Case 2:
Case 3:
FIGURE 11. COMPENSATION CONFIGURATION FOR
C
while observing the transient performance on an
R
FB
LOAD-LINE REGULATED ISL6219 CIRCUIT
R
C
-------------------
2π LC
f
R
C
C
C
0
V
-------------------
2π LC
R
C
+
C
C
-
1
DROOP
>
R
C
C
=
=
C
----------------------------- -
2πC ESR
=
=
1
R
=
=
------------------------------------------------------------ -
(
2π
R
0.75V
------------------------------------------------ -
C
≤
FB
2πV
R
2
----------------------------------- -
2πV
FB
f
(
)
1
C
>
0
(OPTIONAL)
FB
V
--------------------------------------------
2
C
0.75V
f
<
PP
----------------------------------------- -
0.75 V
f
0
PP
14
PP
2πf
----------------------------------- -
0
IN
----------------------------- -
2πC ESR
0.75V
2
0.75 V
2π f
(
)
V
R
(
0.75V
R
2π
ESR
0
PP
FB
IN
FB
V
(
COMP
1
0
IN
)
VSEN
pp
2
IN
R
V
f
f
0
0
IN
(
f
pp
FB
) C
FB
IN
0
ESR
C
2
LC
L
L
)
LC
. Slowly increase the
LC
)
(EQ. 17)
PP
is
C
Equations 17 unless some performance issue is noted.
The optional capacitor C
noise away from the PWM comparator (see Figure 5). Keep
a position available for C
frequency capacitor of between 22pF and 150pF in case any
jitter problem is noted.
COMPENSATION WITHOUT LOAD-LINE REGULATION
The non load-line regulated converter is accurately modeled
as a voltage-mode regulator with two poles at the L-C
resonant frequency and a zero at the ESR frequency. A type
III controller, as shown in Figure 12, provides the necessary
compensation.
The first step is to choose the desired bandwidth, f
compensated system. Choose a frequency high enough to
assure adequate transient performance but not higher than
1/3 of the switching frequency. The type-III compensator has
an extra high-frequency pole, f
added noise rejection or to assure adequate attenuation at
the error-amplifier high-order pole and zero frequencies. A
good general rule is to chose f
if desired. Choosing f
problems with too much phase shift below the system
bandwidth.
In the solutions to the compensation equations, there is a
single degree of freedom. For the solutions presented in
Equations 18, R
compensation components are then selected according to
Equations 18.
C
FIGURE 12. COMPENSATION CIRCUIT FOR ISL6219 BASED
will not need adjustment. Keep the value of C
C
R
1
1
R
R
C
FB
CONVERTER WITHOUT LOAD-LINE
REGULATION.
=
FB
C
--------------------------------------------------------------------- -
0.75 V
1
V
+
-
is selected arbitrarily. The remaining
DROOP
=
R
V
HF
C
---------------------------------------- -
PP
IN
C
LC C ESR
2
to be lower than 10 f
2


2
, is sometimes needed to bypass
2π
, and be prepared to install a high-
C
2π f
–
R
C


FB
2
HF
HF
(
f
HF
0
f


HF
. This pole can be used for
= 10 f
COMP
LC 1
VSEN
)
LC
FB
–
0


, but it can be higher
0
can cause
C
0
from
, of the