NCV8508DW50 데이터 시트보기 (PDF) - ON Semiconductor
부품명
상세내역
제조사
NCV8508DW50 Datasheet PDF : 26 Pages
| |||
NCV8508
APPLICATION NOTES
Calculating Power Dissipation in a Single Output
Linear Regulator
The maximum power dissipation for a single output
regulator (Figure 40) is:
PD(max) + [VIN(max) * VOUT(min)]āIOUT(max)
(1)
) VIN(max)IQ
where:
VIN(max) is the maximum input voltage,
VOUT(min) is the minimum output voltage,
IOUT(max) is the maximum output current for the
application, and
IQ is the quiescent current the regulator consumes at
IOUT(max).
IIN
VIN
SMART
REGULATOR®
IOUT
VOUT
} Control
Features
IQ
Figure 40. Single Output Regulator with Key
Performance Parameters Labeled
Once the value of PD(max) is known, the maximum
permissible value of RqJA can be calculated:
RqJA
+
150°C *
PD
TA
(2)
The value of RqJA can then be compared with those in the
package section of the data sheet. Those packages with
RqJAs less than the calculated value in Equation 2 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.
Heatsinks
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 RqJA:
RqJA + RqJC ) RqCS ) RqSA
(3)
where:
RqJC = the junction-to-case thermal resistance,
RqCS = the case-to-heatsink thermal resistance, and
RqSA = the heatsink-to-ambient thermal resistance.
RqJC appears in the package section of the data sheet. Like
RqJA, it too is a function of package type. RqCS and RqSA are
functions of the package type, heatsink and the interface
between them. These values appear in data sheets of
heatsink manufacturers.
http://onsemi.com
22
Share Link: 