NCV8509 ON Semiconductor, NCV8509 Datasheet - Page 15

• Manufacturer Part Number: NCV8509
• Description: Dual 100 Ma Output Ldo Voltage Regulator W/sequenced Output
• Manufacturer: ON Semiconductor

permissible value of R
package section of the data sheet. Those packages with
Once the value of P
The value of R
Figure 51. 16 Lead SOW (Exposed Pad), qJA as a
Thickness), Board Material = 0.0625, G-10/R-4
100
90
80
70
60
50
40
Function of the Pad Copper Area (2 oz. Cu
0
V
IN1
4.5 V
qJA
R qJA + 150°C *
200
can then be compared with those in the
V IN1 t V REF ) V SAT
V IN2 + V IN1 * V SAT
qJA
Copper Area (mm
IC(max)
can be calculated:
Mode 1
400
P IC
is known, the maximum
T A
V
Max V
I(V
IN2
2
)
IN2
600
) × R
IN
Delta
EX
V REF ) V SAT t V IN1 t V REF ) (I OUT2
V IN2 + V REF
Figure 50. V
NCV8509 Series
http://onsemi.com
800
(8)
Mode 2
15
Shunt On
IN
R
the die temperature below 150°C.
dissipate the heat generated by the IC, and an external
heatsink will be required.
Heat Sinks
package to improve the flow of heat away from the IC and
into the surrounding air.
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of R
where:
R
functions of the package type, heatsink and the interface
between them. These values appear in heat sink data sheets
of heat sink manufacturers.
Shunt
qJA
qJA
In some cases, none of the packages will be sufficient to
A heat sink effectively increases the surface area of the
Each material in the heat flow path between the IC and the
R
R
R
R
qJC
qCS
qSA
qJC
's less than the calculated value in equation 2 will keep
, it too is a function of package type. R
= the junction-to-case thermal resistance,
appears in the package section of the data sheet. Like
= the case-to-heatsink thermal resistance, and
= the heatsink-to-ambient thermal resistance.
R qJA + R qJC ) R qCS ) R qSA
V IN1 u V REF ) (I OUT2
V IN2 + V IN1 * (I OUT2
Mode 3
qJA
R EX )
:
Shunt Off
R EX )
R EX )
qCS
and R
qSA
are
(9)