EL4421C 22C 41C 42C 43C 44C
Multiplexed-Input Video Amplifiers
Applications Information
Contd
The maximum dissipation a package support is
P
D
max
e
(T
D
max-T
A
max) R
TH
Where T
D
max is the maximum die temper-
ature 150 C for reliability less to re-
tain optimum electrical performance
T
A
max is the ambient temperature
70 for commercial and 85 C for indus-
trial range
R
TH
is the thermal resistance of the
mounted package obtained from data
sheet dissipation curves
The most difficult case is the SO-8 package With
a maximum die temperature of 150 C and a maxi-
mum ambient temperature of 85 the 65 temper-
ature rise and package thermal resistance of
170 W gives a maximum dissipation of 382 mW
This allows a maximum supply voltage of
g
9 2V
for the EL4422 operated in our example If the
%
)
EL4421 were driving a light load (R
PAR
it could operate on
g
15V supplies at a 70 maxi-
mum ambient
behavior is assured In any event keeping signals
within guaranteed compliance limits will assure
freedom from overload problems
The input and output ranges are substantially
constant with temperature
Power Supplies
The mux-amps work well on any supplies from
g
3V to
g
15V The supplies may be of different
voltages as long as the requirements of the Gnd
pin are observed (see the Switching Characteris-
tics section for a discussion) The supplies should
be bypassed close to the device with short leads
4 7
mF
tantalum capacitors are very good and no
smaller bypasses need be placed in parallel Ca-
pacitors as small as 0 01
mF
can be used if small
load currents flow
Single-polarity supplies such as
a
12V with
a
5V can be used as described in the Switching
Characteristics section The inputs and outputs
will have to have their levels shifted above
ground to accommodate the lack of negative sup-
ply
The dissipation of the mux-amps increases with
power supply voltage and this must be compati-
ble with the package chosen This is a close esti-
mate for the dissipation of a circuit
P
D
e
2V
S
c
I
s
max
a
(V
S
– V
O
)
c
V
O
R
PAR
Where I
s
max is the maximum supply cur-
rent
V
S
is the
g
supply voltage (as-
sumed equal)
V
O
if the output voltage
R
PAR
is the parallel of all resistors
loading the output
For instance the EL4422 draws a maximum of
14 mA and we might require a 2V peak output
into 150X and a 270X
a
270X feedback divider
The R
PAR
is 117X The dissipation with
g
5V
supplies is 191 mW The maximum Supply volt-
age that the device can run on for a given P
D
and
the other parameter is
V
S
max
e
(P
D
a
V
O2
R
PAR
) 2Is
a
V
O
R
PAR
)
12
x
The EL4441 through EL4444 can operate on
g
12V supplies in the SO package and all parts
can be powered by
g
15V supplies in DIP pack-
ages
Output Loading
The output stage of the mux-amp is very power-
ful and can source 80 mA and sink 120 mA Of
course this is too much current to sustain and
the part will eventually be destroyed by excessive
dissipation or by metal traces on the die opening
The metal traces are completely reliable while de-
livering the 30 mA continuous output given in
the Absolute Maximum Ratings table in this
data sheet or higher purely transient currents
Gain or gain accuracy degrades only 10% from
no load to 100X load Heavy resistive loading will
degrade frequency response and video distortion
only a bit becoming noticeably worse for loads
k
100X
ELANTEC [ ELANTEC SEMICONDUCTOR ]
