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