ISL6322_07 INTERSIL [Intersil Corporation], ISL6322_07 Datasheet - Page 33

• Manufacturer Part Number: ISL6322_07
• Description: Four-Phase Buck PWM Controller with Integrated MOSFET Drivers and I2C Interface for Intel VR10, VR11, and AMD Applications
• Manufacturer: INTERSIL [Intersil Corporation]

The total gate drive power losses are dissipated among the
resistive components along the transition path and in the
bootstrap diode. The portion of the total power dissipated in
the controller itself is the power dissipated in the upper drive
path resistance, P
P
The rest of the power will be dissipated by the external gate
resistors (R
(R
the typical upper and lower gate drives turn-on transition
path. The total power dissipation in the controller itself, P
can be roughly estimated with Equation 31.
P
P
P
R
P
DR_UP
FIGURE 20. TYPICAL LOWER-GATE DRIVE TURN-ON PATH
DR
DR_UP
DR_LOW
FIGURE 19. TYPICAL UPPER-GATE DRIVE TURN-ON PATH
EXT1
PVCC
BOOT
GI1
PVCC
=
and R
P
=
, and in the boot strap diode, P
=
DR_UP
=
PHASE
R
=
P
---------------------
R
⎛
⎜
⎝
R
G1
G1
LO2
Qg_Q1
--------------------------------------
R
GI2
BOOT
HI2
⎛
⎜
⎝
R
R
HI1
--------------------------------------
R
3
LO1
+
and R
HI1
HI2
) of the MOSFETs. Figures 19 and 20 show
+
R
-------------
R
N
+
P
GI1
DR_UP
HI1
Q1
R
R
+
DR_LOW
HI2
EXT1
R
G2
LGATE
EXT2
UGATE
) and the internal gate resistors
, the lower drive path resistance,
+
+
--------------------------------------- -
R
+
33
LO1
--------------------------------------- -
R
P
R
LO2
BOOT
EXT2
R
R
G2
R
+
LO1
R
G
G1
+
R
LO2
G
EXT1
R
+
=
R
C
EXT2
GI2
(
GD
R
BOOT
R
C
I
C
Q
GI1
GD
G2
GS
⎞ P
⎟
⎠
C
⋅
VCC
⋅
⎞ P
⎟
⎠
GS
+
---------------------
⋅
.
S
Qg_Q1
---------------------
R
-------------
N
Qg_Q2
GI2
S
3
Q2
)
2
D
D
Q2
C
(EQ. 31)
Q1
DS
C
DS
DR
,
ISL6322
Inductor DCR Current Sensing Component
Selection
The ISL6322 senses each individual channel’s inductor
current by detecting the voltage across the output inductor
DCR of that channel (as described in “Continuous Current
Sampling” on page 13). As Figure 21 illustrates, an R-C
network is required to accurately sense the inductor DCR
voltage and convert this information into a current, which is
proportional to the total output current. The time constant of
this R-C network must match the time constant of the
inductor L/DCR.
The R-C network across the inductor also sets the
overcurrent trip threshold for the regulator. Before the R-C
components can be selected, the desired overcurrent
protection level should be chosen. The minimum overcurrent
trip threshold the controller can support is dictated by the
DCR of the inductors and the number of active channels. To
calculate the minimum overcurrent trip level, I
Equation 32, where N is the number of active channels, and
DCR is the individual inductor’s DCR.
The overcurrent trip level of the ISL6322 cannot be set any
lower then the I
minimum overcurrent trip level is desired, do the
following steps to choose the component values for the
R-C current sensing network:
I
OCP min
1. Choose an arbitrary value for C
MOSFET
DRIVER
value is 0.1µF.
,
ISL6322 INTERNAL CIRCUIT
SAMPLE
FIGURE 21. DCR SENSING CONFIGURATION
=
I
n
0.0375 N
-------------------------- -
DCR
OCP,min
UGATE(n)
LGATE(n)
I
SEN
⋅
+
-
level calculated above. If the
V
R
V
IN
ISEN
C
(s)
-
1
R
INDUCTOR
. The recommended
1
L
V
ISEN-(n)
ISEN+(n)
L
I
(s)
L
V
C
DCR
*R
-
R
(s)
C
2*
1
2
OCP,min
-
is OPTIONAL
February 15, 2007
C
V
OUT
(EQ. 32)
, use
FN6328.1
OUT