NCV8675 ON Semiconductor, NCV8675 Datasheet - Page 12

• Manufacturer Part Number: NCV8675
• Description: 5.0v, 3.3v/350ma Very Low Quiescent Current Ldo W/ Reset, Delay Reset
• Manufacturer: ON Semiconductor

Calculating Power Dissipation
in a Single Output Linear Regulator
regulator (Figure 36) is:
P D(max) + [V I(max) * V OUT(min) ] I OUT(max)
where
permissible value of R
package section of the data sheet. Those packages with
R
keep 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 34 will
OUT(max)
q
Figure 36. Single Output Regulator with Key
I(max)
OUT(min)
V
100
75
50
25
I
0
0
Performance Parameters Labeled
) V I(max) I q
I
100
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 *
D
can then be compared with those in the
200
2
PAK 2 oz
qJA
REGULATOR®
D(max)
}
COPPER AREA (mm
can be calculated:
300
SMART
Control
Features
Q(max)
Figure 37.
P D
is known, the maximum
400
Iq
D
.
T A
2
500
PAK 1 oz
I
OUT
600
2
)
700
V
http://onsemi.com
OUT
800
(1)
NCV8675
(2)
12
900
Heatsinks
package to improve the flow of heat away from the IC and
into the surrounding air.
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of R
where
R
functions of the package type, heatsink and the interface
between them. These values appear in heatsink data sheets
of heatsink manufacturers.
discussed in the ON Semiconductor application note
AN1040/D.
qJA
100
A heatsink effectively increases the surface area of the
Each material in the heat flow path between the IC and the
R
Thermal, mounting, and heatsinking considerations are
0.1
10
qJC
0.000001
1
R
R
R
, it too is a function of package type. R
qJC
qCS
qSA
appears in the package section of the data sheet. Like
Figure 38. NCV8675 @ PCB Cu Area 100 mm
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.
0.0001
D
2
PAK
PCB Cu thk 1 oz
PULSE TIME (sec)
qJA
:
0.01
1
qCS
Single Pulse
and R
100
qSA
are
(3)
2