ISL6313 INTERSIL [Intersil Corporation], ISL6313 Datasheet - Page 26

• Manufacturer Part Number: ISL6313
• Description: Two-Phase Buck PWM Controller with Integrated MOSFET Drivers for Intel 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
power will be dissipated by the external gate resistors (R
and R
the MOSFETs. Figures 18 and 19 show the typical upper and
lower gate drives turn-on transition path. The total power
dissipation in the controller itself, P
estimated as:
P
P
P
R
P
DR_UP
FIGURE 19. TYPICAL LOWER-GATE DRIVE TURN-ON PATH
DR
DR_UP
DR_LOW
FIGURE 18. TYPICAL UPPER-GATE DRIVE TURN-ON PATH
EXT1
PVCC
BOOT
PVCC
=
G2
P
=
, and in the boot strap diode, P
) and the internal gate resistors (R
=
DR_UP
=
PHASE
R
=
P
---------------------
R
⎛
⎜
⎝
R
G1
LO2
Qg_Q1
--------------------------------------
R
BOOT
HI2
⎛
⎜
⎝
R
R
HI1
--------------------------------------
R
3
LO1
+
HI1
HI2
+
R
-------------
R
N
+
P
DR_UP
GI1
HI1
Q1
R
R
+
DR_LOW
HI2
EXT1
R
LGATE
EXT2
UGATE
, the lower drive path resistance,
+
+
--------------------------------------- -
R
+
26
LO1
--------------------------------------- -
R
P
R
LO2
BOOT
EXT2
R
R
G2
R
+
LO1
R
G
DR
G1
+
R
LO2
G
EXT1
R
+
, can be roughly
=
R
C
EXT2
GI2
BOOT
(
GD
R
R
C
I
C
Q
GI1
GD
G2
GS
⎞ P
⎟
⎠
C
⋅
GI1
VCC
⋅
⎞ P
⎟
⎠
GS
+
. The rest of the
---------------------
⋅
S
Qg_Q1
---------------------
R
-------------
N
and R
Qg_Q2
GI2
S
3
Q2
)
2
D
D
GI2
Q
C
(EQ. 33)
2
DS
Q
C
) of
1
G1
DS
ISL6313
Inductor DCR Current Sensing Component
Selection
The ISL6313 senses each individual channel’s inductor
current by detecting the voltage across the output inductor
DCR of that channel (As described in the “Continuous Current
Sensing” on page 12). As Figure 20 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.
Follow the steps below to choose the component values for
this RC network.
Once the R-C network components have been chosen, the
effective internal R
R
loop as well as the gain of the channel-current balance loop
and the overcurrent trip level. The effective internal R
resistance is set through a single resistor on the RSET pin,
R
Use Equation 35 to calculate the value of R
Equation 35, DCR is the DCR of the output inductor at room
temperature, I
R
1. Choose an arbitrary value for C
2. Plug the inductor L and DCR component values, and the
ISEN
SET
1
=
MOSFET
value is 0.1μF.
value for C
calculate the value for R
DRIVER
.
-------------------------
DCR C
resistance sets the gain of the load line regulation
FIGURE 20. DCR SENSING CONFIGURATION
SENSE
L
⋅
I
n
ISL6313 INTERNAL CIRCUIT
1
OCP
1
UGATE
LGATE
I
chosen in step 1, into Equation 34 to
SEN
ISEN
is the desired overcurrent trip level, and
+
-
resistance must then be set. The
1
V
R
V
.
IN
ISEN
C
(s) -
1
R
INDUCTOR
. The recommended
1
L
V
ISEN-
ISEN+
RSET
L
I
(s)
L
V
R
C
DCR
SET
SET
-
(s)
C
1
-
. In
March 5, 2007
VCC
C
(EQ. 34)
V
ISEN
OUT
FN6448.0
OUT