IR3084AMPBF International Rectifier, IR3084AMPBF Datasheet - Page 37

• Manufacturer Part Number: IR3084AMPBF
• Description: IC XPHASE CONTROL 28-MLPQ
• Manufacturer: International Rectifier
• Series: XPhase™r

Specifications of IR3084AMPBF

• Applications: Processor
• Current - Supply: 14mA
• Voltage - Supply: 9.5 V ~ 16 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 28-MLPQ
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Over Current Setting Resistor R
Assume that room temperature is 25ºC and the target PCB temperature is 100 ºC. The phase IC die temperature
is usually about 1 ºC higher than that of phase IC and the inductor temperature is close to PCB temperature.
Calculate the Inductor’s DC resistance at 100 ºC using Equation (14);
The current sense amplifier gain is 34 at 25ºC, and its gain at 101ºC is calculated using Equation (15),
Here we will set the over current shutdown threshold to 155A at maximum operating temperature. From Figure
14 on page 23, the bias current of the OCSET pin (I
amplifier input offset voltage calculated previously is 0.574mV, which includes the offset created by the current
sense amplifier input resistor mismatch.
Calculate the constant K
(17);
Finally, calculate the over-current setting resistor using Equation (16);
G
R

K
R
L_MAX
OCSET
CS_MIN
P
(
155
Page 37 of 45

7
(

V



R
I
. 0
[
L_ROOM

G
77
R
V
CS_ROOM
LIMIT
O
n
*
)
10


V
[1


I
O
3
P,
LIMIT

R


/(
[1
the ratio of inductor peak current over average current in each phase using Equation
L_MAX
3850*10

L
1

/


n
1470*10
V
. 0

I
OCSET
273
(1


6

f

SW

K

(T


P
. 0
L_MAX
6
)
) 2
574


(T
V


CS_TOFST
IC_MAX
*
(
T
12
10
ROOM
OCSET


3
. 1
)

)]
]

18
T


42
ROOM
) is 42.5µA with R
)
G
0.

I
5 .
60
CS
30
OCSET
. 1
*10
*
)]
_
18
2 .
MIN
10

/(


3
34
3
220


[1
155

15.8K
*

[1
10
3850*10
7 /
OSC


1470*10
9


=30.1kΩ. The total current sense
12


6

400
(100

6

*
10
(101

IR3084A
25)]
3
3/3/2009


) 2

25)]
. 0

77
. 0

273
m
30.

2