IR3521MTRPBF International Rectifier, IR3521MTRPBF Datasheet - Page 29

• Manufacturer Part Number: IR3521MTRPBF
• Description: IC CTRL XPHASE3 SVID 32-MLPQ
• Manufacturer: International Rectifier
• Series: XPhase3™r

Specifications of IR3521MTRPBF

• Applications: Processor
• Current - Supply: 10mA
• Voltage - Supply: 4.75 V ~ 7.5 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: *
• Package: 32-Lead MLPQ
• Circuit: X-Phase Control IC
• Switch Freq (khz): 250kHz to 1.5MHz
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Over Current Setting Resistor R
The inductor DC resistance is utilized to sense the inductor current. The copper wire of inductor has a constant
temperature coefficient of 3850 ppm/°C, and therefore the maximum inductor DCR can be calculated from (7), where
R
respectively.
The total input offset voltage (V
(V
resistor R
The over-current limit is set by the external resistor R
I
CHARACTERISTICS Table. G
over the average current in each phase and can be calculated using equation (10).
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
No Load Offset Setting Resistor RFB11, RFB13, RTHERM1 and Adaptive Voltage Positioning Resistor
RDRP11 for Output1
Define R
offset voltage V
the equation in the ELECTRICAL CHARACTERISTICS Table, the effective offset resistor value, R
determined from equation (12).
OCSET
L_MAX
CS_OFST)
is the bias current of OCSET pin and can be calculated with the equation located in the ELECTRICAL
VCCLFB1
and R
FB_R
CS
of the amplifier itself and that created by the amplifier input bias current flowing through the current sense
.
as the effective offset resistor at room temperature equals to R
L_ROOM
O_NLOFST
, and calculate R
are the inductor DCR at maximum temperature, T
V
R
R
K
R
(offset above the DAC voltage) and calculating the sink current from the FB1 pin I
VCCLFB
L
CS
OCSET
P
_

_
MAX
TOFST
(
V
CS

2
I

VCCLFB2
VCCLFB1
CS_TOFST
[


OCSET
R
is the gain of the current sense amplifier. K
I
C
R
V

VDAC
LIMIT
R
L
O
VDAC
VCCL
n
VCCLFB
_
V
)
ROOM

CS
V


O
_

from (11).
R
I
0
and R
OFST

1
O
), of the phase IC’s current sense amplifier, is the sum of input offset
/(
L
SR
5 .

*
. 1
L
_
/
I
1 [
. 1

23
MAX
n
SINK
DOWN

23

V

3
3850
VCCLFB2
2 .
I
C
I


VDAC

CSIN
1 (
f
10
SW
Page 29

*
OCSET

10

2
K
15


P

) 2
6
)
R


CS
(
V
as defined in (9). I
T
CS
L
_
_
MAX
TOFST

]
T

L
_
G
ROOM
CS
L_MAX,
/
I
OCSET
)]
P
LIMIT
is the ratio of inductor peak current
FB11
and room temperature, T
is the required over-current limit.
//(R
(5)
(6)
(7)
(8)
(9)
(10)
(11)
FB13
+R
THERM1
IR3521
V3.03
). Given the
FB1,
FB1,
L
_
can be
ROOM,
using