ISL6334CCRZ Intersil, ISL6334CCRZ Datasheet - Page 15

• Manufacturer Part Number: ISL6334CCRZ
• Description: IC CTRLR PWM SYNC BUCK 40-QFN
• Manufacturer: Intersil

Specifications of ISL6334CCRZ

• 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
• Rohs Compliant: YES
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

INDUCTOR DCR SENSING
An inductor’s winding is characteristic of a distributed
resistance, as measured by the DCR (Direct Current
Resistance) parameter. Consider the inductor DCR as a
separate lumped quantity, as shown in Figure 4. The
channel current I
pass through the DCR. Equation 4 shows the s-domain
equivalent voltage across the inductor V
A simple R-C network across the inductor extracts the DCR
voltage, as shown in Figure 4.
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
V
V
C
L
s ( )
s ( )
CURRENT
=
SENSE
=
ISL6334B, ISL6334C
FIGURE 4. DCR SENSING CONFIGURATION
⎛
⎝
-------------------------------------------------------------------- -
C
I
s
L
I
n
I
SEN
⋅
⋅
is replicated across the sense resistor R
-------------
DCR
(
ISL6596
s L
L
⋅
(
=
s RC
L
+
PWM(n)
+
⋅
, flowing through the inductor, will also
I
L
DCR
1
----------------- -
R
⎞
⎠
DCR
⋅
ISEN
+
(
DCR I
)
1
+
-
)
V
IN
15
⋅
L
C
)
, can be shown to be
ISEN-(n)
ISEN+(n)
INDUCTOR
R
L
L
. See Equation 5.
I
L
s ( )
V
L
SEN
L
V
.
DCR
C
-
C
(s)
, is proportional
-
R
C
ISEN(n)
T
ISL6334B, ISL6334C
C
ISEN
V
OUT
OUT
(EQ. 4)
(EQ. 5)
C
.
is
T
,
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
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 ISL6334B, ISL6334C
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
I
I
SEN
SEN
SENSE
FIGURE 5. SENSE RESISTOR IN SERIES WITH INDUCTORS
=
=
I
I
L
in series with each output inductor can serve as the
L
CURRENT
⋅
⋅
SENSE
I SEN
----------------- -
R
R
-----------------------
ISL6334B, ISL6334C
DCR
R
ISEN
SENSE
I
ISEN
n
ISEN
=
SEN
SEN
I L
and C
R SENSE
------------------------- -
.
n
, is driven by the value of the sense
R
T
ISEN
from each active channel is summed
is needed to match the time delay
T
+
-
AVG
ISEN
(R
ISEN
provides a measure of the
ISEN-(n)
ISEN+(n)
and C
L
x C
ISEN
T
to keep the time
T
T
) close to 27ns.
R
(R
, or the integrated
I
SENSE
L
ISEN
R
C
ISEN(n)
T
C
x C
V
OUT
OUT
August 31, 2010
T
SENSE
) close to
(EQ. 7)
FN6689.2
(EQ. 6)
T
to
.