EL4421C/22C/41C/42C/43C/44C
Multiplexed-Input Video Amplifiers
Applications Information Ð Contd.
behavior is assured. In any event, keeping signals
within guaranteed compliance limits will assure
freedom from overload problems.
The maximum dissipation a package support is
e
P , max
D
(T , max-T , max)/R
D A TH
Where T , max is the maximum die temper-
D
The input and output ranges are substantially
constant with temperature.
ature, 150 C for reliability, less to re-
tain optimum electrical performance
§
T , max is the ambient temperature,
A
Power Supplies
The mux-amps work well on any supplies from
70 for commercial and 85 C for indus-
trial range
§
§
g
g
3V to 15V. The supplies may be of different
R
TH
is the thermal resistance of the
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.
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.
§
g
This allows a maximum supply voltage of 9.2V
for the EL4422 operated in our example. If the
a
Single-polarity supplies, such as
a
12V with
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.
%
EL4421 were driving a light load (RPARx ),
g
it could operate on 15V supplies at a 70 maxi-
§
mum ambient.
The EL4441 through EL4444 can operate on
g
can be powered by 15V supplies in DIP pack-
12V supplies in the SO package, and all parts
g
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:
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.
e
c a
I ,max (V –V ) V /R
s S PAR
c
P
2V
D
S
O O
Where I , max is the maximum supply cur-
s
rent
g
supply voltage (as-
V
is the
sumed equal)
S
V
if the output voltage
O
R
is the parallel of all resistors
PAR
loading the output
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
For instance, the EL4422 draws a maximum of
14 mA and we might require a 2V peak output
a
into 150X and a 270X 270X feedback divider.
g
The R
is 117X. The dissipation with 5V
supplies is 191 mW. The maximum Supply volt-
PAR
k
100X.
age that the device can run on for a given P and
D
the other parameter is
2
/R
e
V , max (P
a
a
)/2Is V /R
O
V
)
PAR
S
D
O
PAR
12
ELANTEC [ ELANTEC SEMICONDUCTOR ]
