ISL6316IRZ-T Intersil, ISL6316IRZ-T Datasheet - Page 25

• Manufacturer Part Number: ISL6316IRZ-T
• Description: IC CTRLR PWM 4PHASE ENH 40-QFN
• Manufacturer: Intersil

Specifications of ISL6316IRZ-T

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 275kHz
• Duty Cycle: 66.7%
• Voltage - Supply: 4.75 V ~ 5.25 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-VFQFN, 40-VFQFPN
• Frequency-max: 275kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The feedback resistor, R
outlined in Load-Line Regulation Resistor. Select a target
bandwidth for the compensated system, f
bandwidth must be large enough to assure adequate transient
performance, but smaller than 1/3 of the per-channel
switching frequency. The values of the compensation
components depend on the relationships of f
frequency and the ESR zero frequency. For each of the three
cases which follow, there is a separate set of equations for the
compensation components.
Case 1:
Case 2:
Case 3:
FIGURE 19. COMPENSATION CONFIGURATION FOR
R
FB
LOAD-LINE REGULATED ISL6316 CIRCUIT
R
C
-------------------
2π LC
R
C
-------------------
2π LC
f
R
C
V
0
+
C
C
-
C
C
C
C
DROOP
R
>
1
1
C
=
=
=
=
----------------------------- -
2πC ESR
=
=
R
C
R
------------------------------------- -
2πV
-------------------------------------------------------------- -
(
FB
R
0.75V
------------------------------------------------ -
2π
2πV
2
>
≤
FB
FB
FB
C
(
(OPTIONAL)
, has already been chosen as
1
f
0.75V
f
)
0
C
0
2πf
-------------------------------------- -
P-P
V
----------------------------------------------
2
P-P
<
----------------------------------------- -
0.75 V
25
P-P
f
IN
0
----------------------------- -
2πC ESR
2π f
0.75V
0.75V
2
0
R
)
(
0.75 V
R
V
IN
V
IDROOP
FB
(
ESR
2π
P-P
FB
P-P
COMP
0
VDIFF
(
IN
1
f
V
0
)
f
IN
IN
P-P
2
0
(
FB
R
) C
IN
ESR
f
LC
FB
0
L
2
)
L
0
LC
. The target
LC
)
0
to the L-C pole
(EQ. 32)
ISL6316
In Equation 32, 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
peak sawtooth signal amplitude as described in Figure 7 and
Electrical Specifications.
The optional capacitor C
noise away from the PWM comparator (see Figure 20). Keep
a position available for C
frequency capacitor of between 22pF and 150pF in case any
leading-edge jitter problem is noted.
Once selected, the compensation values in Equation 32
assure a stable converter with reasonable transient
performance. In most cases, transient performance can be
improved by making adjustments to R
value of R
oscilloscope until no further improvement is noted. Normally,
C
Equation 32 unless some performance issue 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 20, 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 choose f
desired. Choosing f
problems with too much phase shift below the system
bandwidth.
FIGURE 20. COMPENSATION CIRCUIT FOR ISL6316 BASED
C
will not need adjustment. Keep the value of C
C
R
1
1
C
while observing the transient performance on an
CONVERTER WITHOUT LOAD-LINE
REGULATION
R
HF
FB
R
C
to be lower than 10f
C
2
2
2
, is sometimes needed to bypass
, and be prepared to install a high-
HF
C
C
= 10f
HF
. This pole can be used for
IDROOP
0
COMP
VDIFF
, but it can be higher if
FB
C
. Slowly increase the
P-P
0
is the peak-to-
can cause
December 12, 2006
C
0
from
, of the
FN9227.1