ir3092 International Rectifier Corp., ir3092 Datasheet - Page 30

• Manufacturer Part Number: ir3092
• Description: 2 Phase Opteron, Athlon, Or Vr10.x Control Ic
• Manufacturer: International Rectifier Corp.

MathCAD file to estimate the power dissipation of the IC
Initial Conditions:
Page 30 of 37
The IC will have less power dissipation if using external gate driver supply. For the worst case estimation,
assume using the bias regulator for all the gate drive supply voltage.
1. Quiescent Power dissipation
2. The Power Loss to drive the gate of the MOSFETs
3. The bias regulator Power Loss to supply driving the MOSFETs
4. Total Power Dissipation of the IC:
No.of Phases:
IC Supply Voltage: Vcc
Total High side Driver VCCH supply current(quiescent):
Total Low side Driver VCCL supply Current(quiescent):
Biasout Voltage:
Switching Frequency per phase:
Thermal Impedance of IC: T
The data from the selected MOSFETs:
Total Quiescent Power Dissipation:
With the assumption of the low MOSFET gate resistances, most gate drive losses are dissipated in the
driver circuit.
Where the Ig
bias current required to drive all the MOSFETs.
And the total Junction temperature rising is:
Control FET IR3715Z, Number of Control FET per phase:
Control FET total gate charge:
Synchronous FET IR3717, Number of sync. FET per phase:
Sync FET total gate charge:
n
fsw 10
Preg
Pdiss
2
Pdrv
Vbias
˜
3
n ˜
(
12
Vcc
Vbias fsw
Pq
Pq
JA
˜
( )
7.5
(
V

nc Qgc

( )
˜
Pdrv
Vbias
˜
V
(
Qgs
Icq
27
Qgc
fsw
( o C/W)
, IC Supply Current(quiescent):
˜

) Ig


10
˜
Iqh
Preg
ns Qgs
3
33
n ˜
11
200
˜

(
nC
(
Iql
˜
nC
ª ¬
(
)
(
kHz
) Vcc
)
nc Qgc
Pdiss T
)
˜
˜
10
)
˜
#
˜
˜
9
10
JA

Pdiss
"
Iqh
Iql
ns Qgs
3
term in the equation gives the total average
27.281
˜
Preg
5 n ˜
nc
5 n ˜
1.01
) 10
ns
˜
Icq
2
0.158
( o C)
(
(
mA
mA

( )
2
W
9
º ¼
)
)
Pq
29
( )
W
(
mA
0.588
)
06/25/04
Pdrv
( )
W
0.264
IR3092
( )
W