NCV4275 ON Semiconductor, NCV4275 Datasheet - Page 8

• Manufacturer Part Number: NCV4275
• Description: 5v/450ma Ldo W/ Reset And Delay
• Manufacturer: ON Semiconductor

Calculating Power Dissipation
in a Single Output Linear Regulator
regulator (Figure 15) is:
P D(max) + [V I(max) * V Q(min) ] I Q(max)
where
permissible value of R
package section of the data sheet. Those packages with
R
the die temperature below 150°C.
dissipate the heat generated by the IC, and an external
heatsink will be required.
qJA
The maximum power dissipation for a single output
Once the value of P
The value of R
In some cases, none of the packages will be sufficient to
V
V
I
I
's less than the calculated value in Equation 2 will keep
Q(max)
q
Figure 15. Single Output Regulator with Key
V
I(max)
Q(min)
I
Performance Parameters Labeled
) V I(max) I q
I
I
is the maximum input voltage,
is the minimum output voltage,
is the maximum output current for the
application,
is the quiescent current the regulator
consumes at I
qJA
R qJA + 150°C *
can then be compared with those in the
qJA
REGULATOR®
D(max)
}
SMART
can be calculated:
Control
Features
Q(max)
P D
is known, the maximum
Iq
.
T A
I
Q
V
http://onsemi.com
Q
(1)
NCV4275
(2)
8
Heatsinks
package to improve the flow of heat away from the IC and
into the surrounding air.
the outside environment will have a thermal resistance.
Like series electrical resistances, these resistances are
summed to determine the value of R
where
Like R
R
interface between them. These values appear in heatsink
data sheets of heatsink manufacturers.
discussed in the ON Semiconductor application note
AN1040/D.
qSA
A heatsink effectively increases the surface area of the
Each material in the heat flow path between the IC and
R
Thermal, mounting, and heatsinking considerations are
qJC
R
R
R
are functions of the package type, heatsink and the
qJC
qCS
qSA
qJA
appears in the package section of the data sheet.
, it too is a function of package type. R
R qJA + R qJC ) R qCS ) R qSA
is the junction-to-case thermal resistance,
is the case-to-heatsink thermal resistance,
is the heatsink-to-ambient thermal
resistance.
qJA
:
qCS
and
(3)