ncp4303a ON Semiconductor, ncp4303a Datasheet - Page 24

• Manufacturer Part Number: ncp4303a
• Description: Ncp4303a/b Secondary Side Synchronous Rectification Driver For High Efficiency Smps Topologies
• Manufacturer: ON Semiconductor

Where:
R
equivalent resistance (1.55 W)
R
equivalent resistance (7 W)
R
R
Step 3 – IC Consumption Calculation:
consumption is calculated. This power loss is given by the
I
depends on switching frequency and also on the selected
min T
from the min T
for calculating these losses is to measure the I
C
with given Min_Ton and Min_Toff adjust resistors. Refer
also to Figure 54 for typical IC consumption charts when the
driver is not loaded. IC consumption losses can be calculated
as:
CC
drv_low_eq
drv_high_eq
g_ext
g_int
load
P
In this step, power dissipation related to the internal IC
DRV_IC
current and the IC supply voltage. The I
on
= 0 nF and the IC is switching at the target frequency
is the internal gate resistance of the MOSFET
is the external gate resistor (if used)
and T
+
)
is the NCP4303x driver low side switch
1
2
is the NCP4303x driver high side switch
off
@ C
on
1
2
periods because there is current flowing out
@ C
and T
g_ZVS
P
g_ZVS
ICC
off
@ V
+ V
@ V
pins. The most accurate method
clamp
clamp
CC
Figure 53. Equivalent Schematic of Gate Drive Circuitry
2
@ I
@ f
2
CC
@ f
SW
SW
@
@
cc
R
drv_low_eq
current when
R
CC
drv_high_eq
(eq. 10)
current
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R
drv_low_eq
) R
R
drv_high_eq
) R
g_ext
24
g_ext
) R
Step 4 – IC DIE Temperature Arise Calculation:
internal power losses have been determined (driver losses
plus internal IC consumption losses). The SO−8 package
thermal resistance is specified in the maximum ratings table
for a 35 mm thin copper layer with no extra copper plates on
any pin (i.e. just 0.5 mm trace to each pin with standard
soldering points are used).
Where:
P
P
R
T
DRV_IC
Icc
A
qJA
The DIE temperature can be calculated now that the total
The DIE temperature is calculated as:
) R
is the ambient temperature
g_int
is the IC control internal power dissipation
is the thermal resistance from junction to ambient
g_int
T
is the IC driver internal power dissipation
) C
DIE
+ P
g_ZVS
DRV_IC
@ V
clamp
) P
@ f
ICC
SW
@ V
@ R
qJ*A
CC
* V
) T
clamp
A
(eq. 11)
(eq. 9)