CS8321 Cherry Semiconductor Corporation, CS8321 Datasheet - Page 4

• Manufacturer Part Number: CS8321
• Description: Micropower 5V/ 150mA Low Dropout Linear Regulator
• Manufacturer: Cherry Semiconductor Corporation

The maximum power dissipation for a single output regu-
lator (Figure 3) is:
where:
Once the value of P
sible value of R
The value of R
the package section of the data sheet. Those packages
with R
will keep the die temperature below 150¡C.
In some cases, none of the packages will be sufficient to
dissipate the heat generated by the IC, and an external
heatsink will be required.
Figure 4: Single output regulator with key performance parameters
labeled.
V
V
I
tion, and
I
I
OUT(max)
Q
OUT(max)
IN(max)
OUT(min)
P
is the quiescent current the regulator consumes at
V
D(max)
IN
QJA
's less than the calculated value in equation 2
is the maximum input voltage,
.
=
in a Single Output Linear Regulator
is the maximum output current for the applica-
is the minimum output voltage,
I
IN
(
V
Calculating Power Dissipation
IN(max)
QJA
QJA
can then be compared with those in
R
can be calculated:
D(max)
ÐV
QJA
OUT(min)
=
CS8321
is known, the maximum permis-
150¡C - T
)
P
I
I
Q
OUT(max)
D
Circuit Description and Application Notes: continued
A
+V
I
IN(max)
OUT
I
Q
V
OUT
(1)
(2)
4
A heatsink effectively increases the surface area of the
package to improve the flow of heat away from the IC and
into the surrounding air.
Each material in the heat flow path between the IC and the
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed
to determine the value of R
where:
R
R
are functions of the package type, heatsink and the inter-
face between them. These values appear in heatsink data
sheets of heatsink manufacturers.
QJC
QJA
R
R
R
QJC
QCS
QSA
, it too is a function of package type. R
appears in the package section of the data sheet. Like
= the junctionÐtoÐcase thermal resistance,
= the caseÐtoÐheatsink thermal resistance, and
= the heatsinkÐtoÐambient thermal resistance.
R
QJA
= R
QJC
Heatsinks
+ R
QJA
:
QCS
+ R
QSA
QCS
and R
QSA
(3)