EL5421C Elantec Semiconductor, Inc. (acquired by Intersil), EL5421C Datasheet - Page 11

• Manufacturer Part Number: EL5421C
• Description: Quad 12MHz Rail-to-rail I/o Buffer
• Manufacturer: Elantec Semiconductor, Inc. (acquired by Intersil)

maximum junction temperature for the application to
determine if load conditions need to be modified for the
buffer to remain in the safe operating area.
The maximum power dissipation allowed in a package is
determined according to:
where:
The maximum power dissipation actually produced by
an IC is the total quiescent supply current times the total
power supply voltage, plus the power in the IC due to the
loads, or:
when sourcing, and:
when sinking.
Where:
If we set the two P
we can solve for R
ure 3 and Figure 4 provide a convenient way to see if the
device will overheat. The maximum safe power dissipa-
tion can be found graphically, based on the package type
and the ambient temperature. By using the previous
T
T
θ
P
Package
i = 1 to 4 for Quad
V
I
V
Application
I
SMAX
LOAD
AMAX
JA
DMAX
JMAX
S
OUT
= Total Supply Voltage
= Thermal Resistance of the Package
P
P
DMAX
DMA X
i = Maximum Output Voltage of the
i = Load current
= Maximum Ambient Temperature
= Maximum Supply Current Per Channel
= Maximum Junction Temperature
= Maximum Power Dissipation in the
P
=
=
DMAX
Σi V
Σi V
[
[
DMAX
LOAD
S
S
×
×
=
I
I
SMA X
SM AX
T
--------------------------------------------- -
i to avoid device overheat. Fig-
JMAX
equations equal to each other,
+
+
(
(
V
V
Θ
S
OU T
–
+ V
JA
T
–
i V
AMAX
–
OUT
S
- )
i )
×
×
I
I
LOAD
LOAD
i
i
]
]
11
Quad 12MHz Rail-to-Rail Input-Output Buffer
equation, it is a simple matter to see if P
the device’s power derating curves. To ensure proper
operation, it is important to observe the recommended
derating curves shown in Figure 3 and Figure 4.
Unused Buffers
It is recommended that any unused buffer have the input
tied to the ground plane.
Figure 3. Package Power Dissipation vs
Figure 4. Package Power Dissipation vs
1200
1000
600
500
400
300
200
100
800
600
400
200
0
0
0
0
MSOP10 Package Mounted on JEDEC JESD51-7
High Effective Thermal Conductivity Test Board
MSOP10 Package Mounted on JEDEC JESD51-3
Low Effective Thermal Conductivity Test Board
870mW
485mW
Ambient Temperature
Ambient Temperature
25
25
Ambient Temperature (°C)
Ambient Temperature (°C)
50
50
75
75 85
85
EL5421C
100
100
MAX T
MAX T
J
J
=125°C
=125°C
DMAX
125
125
exceeds
150
150