IR3513Z International Rectifier Corp., IR3513Z Datasheet - Page 27

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

Over Current Setting Resistor R
The inductor DC resistance is utilized to sense the inductor current. The copper wire of the inductor has a constant
temperature coefficient of 3850 ppm/°C, and therefore the maximum inductor DCR can be calculated from (5).
R
(T_
The total input offset voltage (V
of the amplifier itself and that created by the amplifier input bias current flowing through the current sense resistor
R
The over-current limit is set by the external resistor, R
limit. I
by equation (9). G
the net inductor current is much smaller than the stand alone phase due to interleaving. The ratio of the peak to
average current in this case can be approximated using (8).
Where
Vout Programming Resistor R
The Feedback pin (FB) is connected to an external resistor divider to set the output voltage. The error amplifier has a
0.8 V reference (Typical) and the output voltage is determined by selecting resistor divider values (See Figure 1).
L_MAX
CS
ROOM),
.
OCSET,
Page 27
and R
respectively.
the bias current of OCSET pin, changes with switching frequency set by resistor R
L_ROOM
CS
is the gain of the current sense amplifier. In a multiphase architecture the peak to peak ripple of
I
n=Number of phases
K
G
I
D=Vo/V
m=Maximum integer that doesn’t exceed (n*D)
are the inductor DCR value at maximum temperature (T
V
K
R
R
Iocset
LIMIT
OCSET
R
CS
P
OCSET
CS
L
P
=Ratio of the peak to average current for the inductor
FB
_
=
=Maximum over current limit
_
=Gain of the current sense amplifier
MAX
TOFST
3
⎡
⎢
⎣
= Determined by the ROSC and given (9)
V
=
CS_TOFST
=
I
=
I
FB1
⋅
=
Vout
[
D
(
R
OCSET
I
I
Rosc
R
=
LIMIT
LIMIT
⋅
FB
and R
L
1 (
V
n
_
1
CS
−
600
ROOM
*
−
/
D
(
_
n
∗
) of current sense amplifier in phase ICs is the sum of input offset (V
0
K
0
OFST
)
)
R
8 .
⋅
FB3
8 .
⋅
Ω
L
L
n
∗
_
⋅
⋅
)
1 [
(
MAX
+
f
D
sw
+
I
−
⋅
CSIN
3850
2
∗
m
n
⋅
1 (
D
)
+
⋅
+
⋅
(
OCSET,
∗
*
1 (
m
K
10
R
n
−
P
+
CS
)
D
−
1
6
+
−
)
∗
V
D
as defined in (7), where I
CS
(
T
)
⎤
⎥
⎦
L
_
_
TOFST
MAX
]
−
∗
T
G
ROOM
CS
/
I
OCSET
)]
LIMIT
L_MAX
(10)
(5)
(6)
(7)
(8)
(9)
is the required over current
) and room temperature
May 11, 2009
OSC
IR3513Z
and is determined
CS_OFST)