CS8361
Application Notes: continued
Heat Sinks
A heat sink 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
QJA
:
R
QJA
= R
QJC
+ R
QCS
+ R
QSA
(3)
where:
R
QJC
= the junctionÐtoÐcase thermal resistance,
R
QCS
= the caseÐtoÐheat sink thermal resistance, and
R
QSA
= the heat sinkÐtoÐambient thermal resistance.
R
QJC
appears in the package section of the data sheet. Like
R
QJA
, it too is a function of package type. R
QCS
and R
QSA
are functions of the package type, heat sink and the inter-
face between them. These values appear in heat sink data
sheets of heat sink manufacturers.
Test & Application Circuits
B+
0.1µF
C1*
V
IN
V
STBY
5V, 100mA
V
DD
R3
C2**
10µF
ESR<8Ω
CS8361
RESET
ENABLE
Adj
MCU
RESET
I/O
R2
R1
Gnd
V
TRK
C3**
SW 8V,
250mA
10µF
ESR<8Ω
Gnd
V
TRK
~ V
STBY
(1 + R1/R2)
For V
TRK
~ 8V, R1/R2 ~ 0.6
* C1 is required if regulator is located far from power supply filter.
** C2 and C3 are required for stability.
Figure 2: 5V, 8V Regulator
B+
0.1µF
C1*
V
IN
V
STBY
5V, 100mA
V
DD
R1
C2**
10µF
ESR<8Ω
CS8361
RESET
ENABLE
Adj
Gnd
V
TRK
MCU
RESET
I/O
C3**
SW 5V,
250mA
10µF
ESR<8Ω
Gnd
* C1 is required if regulator is located far from power supply filter.
** C2 and C3 are required for stability.
Figure 3: Dual 5V Regulator
5
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
