EL4431CS 데이터 시트보기 (PDF) - Elantec -> Intersil

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EL4431CS

EL4430CN EL4430CS EL4431CN EL4431CS

Elantec -> Intersil 

EL4430C EL4431C

Video Instrumentation Amplifiers

Applications Information Contd

Power Supplies

The instrumentation amplifiers work well on any

supplies from g3V to g15 The supplies may be

of different voltages as long as the requirements

of the Gnd pin are observed ( see the Ground Pin

section for a discussion) The supplies should be

bypassed close to the device with short leads

4 7mF tantalum capacitors are very good and no

smaller bypasses need be placed in parallel Ca-

pacitors as low as 0 01mF can be used if small

load currents flow

Single-polarity supplies such as a12V with

a5V can be used where the ground pin is con-

nected to a5V and V- to ground The inputs and

outputs will have to have their levels shifted

above ground to accommodate the lack of nega-

tive supply

The dissipation of the amplifiers 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

PDe 2 c VS c IS max a (VSbVO)

c VO RPAR

where IS max is the maximum supply current

VS is the g 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

16 mA and we might require a 2V peak output

into 150X and a 270X a 270X feedback divider

The RPAR is 117X The dissipation with g5V

supplies is 201 mW The maximum supply volt-

age that the device can run on for a given PD and

the other parameter is

VS max e (PD a VO2 RPAR)

(2IS a VO RPAR)

The maximum dissipation a package can offer is

PD max e (TJ max b TA max) iJA

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

iJA is the thermal resistance of the

mounted package obtained from data-

sheet dissipation curves

The more difficult case is the SO-8 package With

a maximum die temperature of 150 C and a maxi-

mum ambient temperature of 85 C the 65 C tem-

perature rise and package thermal resistance of

170 C W gives a dissipation of 382 mW at 85 C

This allows a maximum supply voltage of g8 5V

for the EL4431 operated in our example If an

x EL4430 were driving a light load (RPAR %)

it could operate on g15V supplies at a 70 C max-

imum ambient

Output Loading

The output stage of the instrumentation amplifi-

ers is very powerful It typically can source

80 mA and sink 120 mA Of course this is too

much current to sustain and the part will eventu-

ally be destroyed by excessive dissipation or by

metal traces on the die opening The metal traces

are completely reliable while delivering the

30 mA 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 100X load Heavy resistive loading will

degrade frequency response and video distortion

for loads k100X

Capacitive loads will cause peaking in the fre-

quency response If capacitive loads must be driv-

en a small-valued series resistor can be used to

isolate it (12X to 51X should suffice) A 22X se-

ries resistor will limit peaking to 2 5 dB with

even a 220 pF load

9

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