irs20955 International Rectifier Corp., irs20955 Datasheet - Page 18

• Manufacturer Part Number: irs20955
• Description: Protected Digital Audio Driver
• Manufacturer: International Rectifier Corp.

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4. P
P
where
f
V
voltage and negative bus voltage
5. P
The power dissipation in high-side comes from
the losses of the logic circuitry and the losses of
driving LO.
where
P
logic circuitry
P
stage to HO
R
typically 10 Ω for the IRS20955S
R
side MOSFET driver, typically 10 Ω for the
IRS20955S
R
MOSFET
Q g = total gate charge of the high- side
MOSFET
=
P
SW
HIGH
LSH
BUS
LDD
LO
O
g(int)
g
(
I
= the PWM switching frequency
QBS
= external gate resistance of the high-side
Level Shifter
= the power dissipation from the gate drive
= equivalent output impedance of HO,
= 0.4 nC x f
= the difference between the positive bus
LSH
HIGH
=
= the power dissipation from the internal
= the internal gate resistance of the high-
⋅
V
P
LDD
BS
: Power Dissipation of the High-Side
: Power Dissipation in High-side
)
+
+
⎛
⎜
⎜
⎝
P
V
HO
BS
sw
⋅
Q
x V
g
⋅
f
BUS
SW
⋅
R
O
+
R
R
g
O
+
R
g
(int)
⎞
⎟
⎟
⎠
Total power dissipation, P
Given R
ambient and junction temperature, T
temperature, can be calculated from the formula
provided below.
th,JA
P
d
, the thermal resistance between the
=
T
P
J
MID
=
+
R
th
IRS20955(S)PbF
P
,
LSM
JA
⋅
P
+
d
d
P
+
, is given by
LOW
T
A
+
<
P
150
HSM
°
+
C
P
J
HIGH
, the junction
.
18