lm6121 National Semiconductor Corporation, lm6121 Datasheet - Page 8

• Manufacturer Part Number: lm6121
• Description: High Speed Buffer
• Manufacturer: National Semiconductor Corporation

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Application Hints
pation in any application is P
simple case of a buffer driving a resistive load as in Figure 2 ,
the maximum DC power dissipation occurs when the output
is at half the supply. Assuming equal supplies, the formula is
P
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, T
by using the formula:
*For best results, use L = 2H
Table 2 shows some values of junction-to-ambient thermal
resistance (θ
D
= I
S
(2V
+
) + V
JA
) for values of L and W for 2 oz. copper:
+2
/4 R
L
FIGURE 2.
.
D
(Continued)
= (T
R
8-Pin DIP
14-Pin SO
(max). This is calculated
J
(max)−T
00922308
Package
FIGURE 3. Copper Heatsink Patterns
A
)/θ
JA
. For the
L (in.)
2
1
2
14-Pin SOIC
8-Pin DIP
TABLE 2.
8
H (in.)
where: T
Using the calculated values for T
required value for junction-to-ambient thermal resistance,
θ
The heatsink for the LM6321 is made using the PC board
copper. The heat is conducted from the die, through the lead
frame (inside the part), and out the pins which are soldered
to the PC board. The pins used for heat conduction are:
Figure 3 shows copper patterns which may be used to
dissipate heat from the LM6321.
0.5
0.5
LM6321N
LM6321M
1
(J–A)
00922310
, can now be found:
Part
temperature
T
00922309
J
A
(max)
(max) is the maximum ambient temperature
θ
JA
T
(˚C/W)
47
69
57
R
(max) = T
θ
is
(J–A)
14-Pin SO
8-Pin DIP
Package
the
= T
TABLE 1.
J
R
maximum
(max) − T
(max)/P(max)
R
(max) and P(max), the
A
(max)
allowable
1, 2, 3, 6, 7,
8, 9, 13, 14
1, 4, 5, 8
Pins
junction