ISL6336BIRZ Intersil, ISL6336BIRZ Datasheet - Page 14

• Manufacturer Part Number: ISL6336BIRZ
• Description: IC CTRLR PWM SYNC BUCK 48-QFN
• Manufacturer: Intersil

Specifications of ISL6336BIRZ

• Applications: Controller, Intel VR11.1
• Voltage - Input: 3 ~ 12 V
• Number Of Outputs: 1
• Voltage - Output: 0.5 ~ 1.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-VQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Inductors” on page 6). Equation 3 is provided to assist in
selecting the correct resistor value.
R
where F
Equation 3 also applies for connecting FS to VCC or GND.
Figure 3 shows the relationship between R
according to Equation 3.
Current Sensing
The ISL6336B senses current continuously for fast response.
The ISL6336B supports inductor DCR sensing, or resistor
sensing techniques. The associated channel current sense
amplifier uses the ISEN inputs to reproduce a signal
proportional to the inductor current, I
I
overcurrent protection.
The internal circuitry, shown in Figures 3 and 4, represents
one channel of an N-Channel converter. This circuitry is
repeated for each channel in the converter, but may not be
active depending on the status of the PWM2, PWM3,
PWM4, PWM5, PWM6 pins, “PWM and PSI# Operation” on
page 12.
The input bias current of the current sensing amplifier is
typically 60nA; less than 5kΩ input impedance is preferred to
minimize the offset error.
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.
SEN
V
T
L
1000
=
900
800
700
600
500
400
300
200
100
=
, is used for current balance, load-line regulation, and the
2.5X10
------------------------- -
I
L
20
F
SW
⋅
SW
FIGURE 3. SWITCHING FREQUENCY vs R
(
s L
is the switching frequency of each phase.
⋅
10
30
+
DCR
L
, flowing through the inductor, will also
40
)
50
14
R
T
60
(kΩ)
L
. The sensed current,
70
L
.
T
80
and F
T
90
SW
,
(EQ. 4)
(EQ. 3)
100
ISL6336B
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 the ISEN- pin, a capacitor,
C
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
serve as the current sense element (see Figure 5). This
technique is more accurate, but reduces overall converter
V
I
SEN
T,
C
is needed to match the time delay between the ISEN-
ISL6336B
INTERNAL CIRCUIT
=
=
CURRENT
⎛
⎝
-------------------------------------------------------------------- -
s
SENSE
I
⋅
L
FIGURE 4. DCR SENSING CONFIGURATION
C
SENSE
-------------
DCR
I
⋅
n
I SEN
----------------- -
R
is replicated across the sense resistor R
L
DCR
ISL6609
(
ISEN
ISEN
s RC
+
⋅
=
SEN
1
in series with each output inductor can
PWM(n)
⎞
⎠
I
L
and C
⋅
+
-------------------
R
(
DCR
DCR I
is driven by the value of the sense
1
ISEN
)
+
-
T
⋅
(R
V
L
IN
)
ISEN
C
, can be shown to be
ISEN-(n)
ISEN+(n)
x C
INDUCTOR
R
L
; see Equation 5.
L
I
T
L
) close to 27ns.
V
s ( )
T
L
SEN
V
to keep the time
DCR
C
-
C
(s)
, is proportional
-
R
(PTC)
C
ISEN(n)
T
August 31, 2010
C
V
ISEN
OUT
OUT
(EQ. 5)
(EQ. 6)
FN6696.2
C
.
is