IR3094M International Rectifier Corp., IR3094M Datasheet - Page 23

• Manufacturer Part Number: IR3094M
• Description: 3 Phase Pwm Controller For Point Of Load
• Manufacturer: International Rectifier Corp.

MathCAD file to estimate the power dissipation of the IC
The full featured Control IC IR3094 contain both Control and 3 phase Gate Drive functions. It also has the
adjustable voltage bias regulator inside to provide MOSFET Drive Voltage. For the thermal consideration,
this Mathcad file step by step shows how to estimate the power dissipation of IR3094 .
Initial Conditions:
Power Dissipation:
The IC will have less power dissipation if using external gate driver supply. For the worst case
estimation, assuming 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:
Total High side Driver VCCH supply current(quiescent): Iqh
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
average bias current required to drive all the MOSFETs.
And the total Junction temperature rising is:
Page 23 of 29
ControI FET IR6637, Number of Control FET per phase:
Control FET total gate charge: Qgc
Synchronous FET IR6612, Number of sync. FET per phase:
Sync FET total gate charge:
Pdrv
fsw 10
Preg
Pdiss
Vbias
n
Vcc
Vbias fsw
˜
3
3
(
n ˜
Vcc
Pq
˜
12
7.5
JA
Pq
˜

(

( )
nc Qgc
Pdrv
V
( )
˜
Vbias
V
27
(
10
Qgs
˜
Icq
fsw
3
(

o
n ˜
) Ig
C/W)

Preg
˜

Iqh
˜
45
450
ª ¬
15
ns Qgs
(
, IC Supply Current(quiescent):
nc Qgc
(

nC
(
˜
nC
˜
Iql
(
)
kHz
Pdiss T
)
) Vcc
˜
)
)
˜

10
˜
ns Qgs

˜
JA
Pdiss
10
9
˜
Iql

term in the equation gives the total
3
) 10
Preg
5 n ˜
nc
˜
5 n ˜
ns

(
o
9
1
(
(
C)
º ¼
mA
mA
(
W
1
)
)
)
Pq
(
W
Icq
Pdrv
)
35
(
W
(
mA
IR3094PBF
)
)
(
W
09/26/05
)