IR3513Z International Rectifier Corp., IR3513Z Datasheet - Page 28

• Manufacturer Part Number: IR3513Z
• Description: Xphase3tm Pol Control Ic
• Manufacturer: International Rectifier Corp.

VCCL Programming Resistor R
Since VCCL voltage is proportional to the MOSFET gate driver loss and inversely proportional to the MOSFET
conduction loss, the optimum voltage should be chosen to maximize the converter efficiency. VCCL linear
regulator consists of an external NPN transistor, a ceramic capacitor and a programmable resistor divider. Pre-
select R
VCCL Capacitor C
The capacitor is selected based on the stability requirement of the linear regulator and the load current to be driven.
The linear regulator supplies the bias and gate drive current of the phase ICs. A 4.7uF normally ensures stable VCCL
performance for most applications.
VCCL Regulator Drive Resistor R
input voltage requirements. The following equation gives an estimate of the average load current of the switching
phase ICs.
Q
I
maximum VCCL, the maximum R
Due to limited pull down capability of the VCCLDRV pin, make sure the following condition is satisfied.
In the above equation, V
condition is not satisfied there is a need to use a device with higher β
instead of a single NPN transistor.
Inductor Current Sensing Capacitor C
The DC resistance of the inductor is utilized to sense the inductor current. Usually the resistor R
in parallel with the inductor are chosen to match the time constant of the inductor, and therefore the voltage across
the capacitor C
the capacitor voltage is different from that of the real inductor current. The time constant mismatch does not affect the
average current sharing among the multiple phases, but affects the current signal ISHARE.
Measure the inductance L and the inductor DC resistance R
follows.
The drive resistor is primarily dependent on the load current requirement of the linear regulator and the minimum
VCCL_C
gb
and Q
is the VCCL current of the controller and n is the number of phases. For a minimum input voltage and a
VCCLFB1
Page 28
gt
are the gate charge of the top and bottom FET, I
CS
, and calculate R
represents the inductor current. If the two time constants are not the same, the AC component of
VCCL
I
I
R
( min) and V
drive
CS
R
=
_
VCCLFB
avg
R
L
VCCLDRV
C
V
VCCLFB2
CS
VCCLFB1
=
R
VCCLDRV
I
(max)
L
(
2
VCCLDRV
Q
=
I
gb
( max) is the minimum and maximum anticipated input voltage. If the above
=
R
VCCL
−
VCCLFB
+
V
CS
required to use the full pull-down current of the VCCL driver is given by
R
0
from (11).
I
VCCLDRV
and R
Q
7 .
(min)
and Resistor R
gt
−
)
−
1
VCCL
I
⋅
*
. 1
drive
n
VCCLFB2
. 1
−
19
+
19
0
_
7 .
(min)
I
avg
VCCL
−
VCCL
/
β
<
_
min
PHS
10
CS
mA
VCCL_PHS
(max)
⋅
(
L
n
. Pre-select the capacitor C
−
) 1
is the VCCL current of the phase IC-s,
+
min
I
VCCL
or Darlington configuration can be used
_
C
(14)
(13)
(15)
(11)
May 11, 2009
CS
(12)
and calculate R
CS
IR3513Z
and capacitor C
CS
CS
as