EL2257CS-T7 데이터 시트보기 (PDF) - Intersil

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EL2257CS-T7

125MHz Single Supply, Clamping Op Amp

Intersil 

EL2257

FIGURE 10.

Short Circuit Current Limit

The EL2257 has internal short circuit protection circuitry that

protect it in the event of its output being shorted to either

supply rail. This limit is set to around 100mA nominally and

reduces with increasing junction temperature. It is intended

to handle temporary shorts. If an output is shorted

indefinitely, the power dissipation could easily increase such

that the part will be destroyed. Maximum reliability is

maintained if the output current never exceeds ±90mA. A

heat sink may be required to keep the junction temperature

below absolute maximum when an output is shorted

indefinitely.

Power Dissipation

With the high output drive capability of the EL2257, it is

possible to exceed the 150°C Absolute Maximum junction

temperature under certain load current conditions.

Therefore, it is important to calculate the maximum junction

temperature for the application to determine if power-supply

voltages, load conditions, or package type need to be

modified for the EL2257 to remain in the safe operating area.

The maximum power dissipation allowed in a package is

determined by:

PDMAX

=

T----J----M----A----X-----------T----A----M----A----X--

θJA

where:

TJMAX = Maximum junction temperature

TAMAX = Maximum ambient temperature

θJA = Thermal resistance of the package

PDMAX = Maximum power dissipation in the package

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 load, or:

PDMAX

=

N × VS × ISMAX + (VS

-

VOUT)

×

-V----O----U----T--

RL

where:

N = Number of amplifiers

VS = Total supply voltage

ISMAX = Maximum supply current per amplifier

VOUT = Maximum output voltage of the application

RL = Load resistance tied to ground

If we set the two PDMAX equations, [1] and [2], equal to each

other, and solve for VS, we can get a family of curves for

various loads and output voltages according to:

VS = -R---------L---------×---------(------T--------J--N----M-(-----I--×-A-S------X--θ--×----J-------RA------T--L------A--)------M+----------AV--------XO--------)-U--+--T---(---V----O----U----T----)--2--

Figure 11 below shows total single supply voltage VS vs. RL

for various output voltage swings for the PDIP and SO

(0.150") packages. The curves assume worst-case

conditions of TA = +85°C and IS = 6.5mA per amplifier.

EL2257 Single Supply Voltage

vs. RLoad for Various

VOUT and Packages

FIGURE 11.

15

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