ISL6334ACRZ Intersil, ISL6334ACRZ Datasheet - Page 15

• Manufacturer Part Number: ISL6334ACRZ
• Description: IC CTRLR PWM 4PHASE BUCK 40-QFN
• Manufacturer: Intersil

Specifications of ISL6334ACRZ

• Applications: Controller, Intel VR11.1
• Voltage - Input: 3 ~ 12 V
• Number Of Outputs: 1
• Voltage - Output: 0.5 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 40-VFQFN, 40-VFQFPN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The voltage on the capacitor V
proportional to the channel current I
If the R-C network components are selected such that the
RC time constant (= R*C) matches the inductor time
constant (= L/DCR), the voltage across the capacitor V
equal to the voltage drop across the DCR, i.e., proportional
to the channel current.
With the internal low-offset current amplifier, the capacitor
voltage V
Therefore, the current out of ISEN+ pin, I
to the inductor current.
Because of the internal filter at ISEN- pin, one capacitor, C
is needed to match the time delay between the ISEN- and
ISEN+ signals. Select the proper C
constant of R
Equation 6 shows that the ratio of the channel current to the
sensed current, I
resistor and the DCR of the inductor.
RESISTIVE SENSING
For accurate current sense, a dedicated current-sense resistor
R
current sense element (see Figure 5). This technique is more
V
ISL6334, ISL6334A INTERNAL CIRCUIT
I
SEN
SENSE
C
s ( )
CURRENT
=
=
SENSE
I
L
in series with each output inductor can serve as the
FIGURE 4. DCR SENSING CONFIGURATION
⎛
⎝
-------------------------------------------------------------------- -
C
s
I
⋅
n
I
SEN
⋅
----------------- -
R
is replicated across the sense resistor R
DCR
-------------
DCR
ISL6596
ISEN
ISEN
L
(
=
s RC
SEN
PWM(n)
+
⋅
I
and C
L
1
----------------- -
R
⎞
⎠
DCR
, is driven by the value of the sense
⋅
ISEN
+
(
DCR I
1
+
T
-
)
(R
V
IN
15
⋅
ISEN
L
C
)
, can be shown to be
ISEN-(n)
ISEN+(n)
x C
T
INDUCTOR
R
L
L
. See Equation 5.
to keep the time
I
T
L
) close to 27ns.
s ( )
V
SEN
L
V
DCR
C
-
C
(s)
, is proportional
-
R
C
ISEN(n)
T
C
ISL6334, ISL6334A
ISEN
V
OUT
(EQ. 5)
(EQ. 6)
OUT
C
.
is
T
,
accurate, but reduces overall converter efficiency due to the
additional power loss on the current sense element R
The same capacitor C
between ISEN- and ISEN+ signals. Select the proper C
keep the time constant of R
27ns.
Equation 7 shows the ratio of the channel current to the
sensed current I
The inductor DCR value will increase as the temperature
increases. Therefore, the sensed current will increase as the
temperature of the current sense element increases. In order
to compensate the temperature effect on the sensed current
signal, a Positive Temperature Coefficient (PTC) resistor can
be selected for the sense resistor R
temperature compensation function of ISL6334, ISL6334A
should be utilized. The integrated temperature compensation
function is described in “External Temperature Compensation”
on page 24.
Channel-Current Balance
The sensed current I
together and divided by the number of active channels. The
resulting average current I
total load current. Channel current balance is achieved by
comparing the sensed current of each channel to the
average current to make an appropriate adjustment to the
PWM duty cycle of each channel with Intersil’s patented
current-balance method.
Channel current balance is essential in achieving the
thermal advantage of multiphase operation. With good
current balance, the power loss is equally dissipated over
multiple devices and a greater area.
I
SEN
ISL6334, ISL6334A INTERNAL CIRCUIT
FIGURE 5. SENSE RESISTOR IN SERIES WITH INDUCTORS
=
I
L
CURRENT
⋅
SENSE
I
R
-----------------------
SEN
R
SENSE
I
n
ISEN
=
SEN
I
L
R
------------------------- -
.
n
R
SENSE
T
ISEN
from each active channel is summed
is needed to match the time delay
+
-
AVG
ISEN
provides a measure of the
ISEN-(n)
ISEN+(n)
and C
L
ISEN
T
R
(R
, or the integrated
I
SENSE
L
ISEN
R
C
ISEN(n)
T
C
x C
V
OUT
OUT
T
May 28, 2009
SENSE
) close to
(EQ. 7)
FN6482.1
T
to
.