EL4430CN Просмотр технического описания (PDF) - Intersil

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EL4430CN

Video Instrumentation Amplifiers

Intersil 

EL4430, EL4431

where

IS, max is the maximum supply current

VS is the ± supply voltage (assumed equal)

VO is the output voltage

RPAR is the parallel of all resistors loading the output

For instance, the EL4431 draws a maximum of 16mA and we

might require a 2V peak output into 150Ω and a

270Ω + 270Ω feedback divider.

The RPAR is 117Ω. The dissipation with ±5V supplies is

201mW. The maximum supply voltage that the device can

run on for a given PD and the other parameter is:

VS, max = (PD + VO2/RPAR)/(2IS + VO/RPAR)

The maximum dissipation a package can offer is:

PD, max = (TJ, max - TA max)/θJA

where

TJ, max is the maximum die junction temperature, 150°C

for reliability, less to retain optimum electrical

performance.

TA, max is the ambient temperature, 70°C for commercial

and 85°C for industrial range.

θJA is the thermal resistance of the mounted package,

obtained from datasheet dissipation curves.

The more difficult case is the SO-8 package. With a

maximum die temperature of 150°C and a maximum

ambient temperature of 85°C, the 65°C temperature rise and

package thermal resistance of 170°C/W gives a dissipation

of 382mW at 85°C. This allows a maximum supply voltage of

±8.5V for the EL4431 operated in our example. If an EL4430

were driving a light load (RPAR→∞), it could operate on

±15V supplies at a 70°C maximum ambient.

Output Loading

The output stage of the instrumentation amplifiers is very

powerful. It typically can source 80mA and sink 120mA. 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 delivering the 30mA continuous output given in

the Absolute Maximum Ratings table in this datasheet, or

higher purely transient currents.

Gain or gain accuracy degrades only 10% from no load to

100Ω load. Heavy resistive loading will degrade frequency

response and video distortion for loads <100Ω.

Capacitive loads will cause peaking in the frequency

response. If capacitive loads must be driven, a small-valued

series resistor can be used to isolate it (12Ω to 51Ω should

suffice). A 22Ω series resistor will limit peaking to 2.5dB with

even a 220pF load.

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