EL5444CSZ datasheet(18/24 Pages) RENESAS

18 / 24 page

EL5144, EL5146, EL5244, EL5246, EL5444

FN7177 Rev 2.00

Page 18 of 24

March 31, 2011

where:

TJMAX = Maximum junction temperature

TAMAX = Maximum ambient temperature

JA = 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

as expressed in Equation 2:

where:

N = Number of amplifiers in the package

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 equal to each other, we

can solve for RL using Equation 3:

Assuming worst case conditions of TA = +85C, VOUT = VS/2V,

VS = 5.5V, and ISMAX = 8.8mA per amplifier, following is a table

of all packages and the minimum RL allowed.

EL5144 Series Comparator Application

The EL5144 series amplifier can be used as a very fast,

single supply comparator. Most op amps used as a

comparator allow only slow speed operation because of

output saturation issues. The EL5144 series amplifier

doesn’t suffer from output saturation issues. Figure 50

shows the amplifier implemented as a comparator. Figure 51

is a graph of propagation delay vs overdrive as a square

wave is presented at the input of the comparator.

Multiplexing with the EL5144 Series Amplifier

Besides normal power-down usage, the CE pin on the

EL5146 and EL5246 series amplifiers also allow for

multiplexing applications. Figure 52 shows an EL5246 with

its outputs tied together, driving a back terminated 75

 video

load. A 3VP-P 10MHz sine wave is applied at Amp A input,

and a 2.4VP-P 5MHz square wave to Amp B. Figure 53

shows the SELECT signal that is applied, and the resulting

output waveform at VOUT. Observe the break-before-make

operation of the multiplexing. Amp A is on and VIN1 is being

passed through to the output of the amplifier. Then Amp A

turns off in about 10ns. The output decays to ground with an

RLCL time constants. 500ns later, Amp B turns on and VIN2

is passed through to the output. This break-before-make

operation ensures that more than one amplifier isn’t trying to

drive the bus at the same time. Notice the outputs are tied

directly together. Isolation resistors at each output are not

necessary.

PART

PACKAGE

MINIMUM RL

EL5144CW

SOT23-5

EL5146CS

SOIC-8

EL5146CN

PDIP-8

EL5244CS

SOIC-8

EL5244CN

PDIP-8

EL5244CY

MSOP-8

EL5246CY

MSOP-10

EL5246CS

SOIC-14

EL5246CN

PDIP-14

EL5444CU

QSOP-16

139

EL5444CS

SOIC-14

EL5444CN

PDIP-14

PDMAX

NVS ISMAX VS



- VOUT

VOUT

----------------



(EQ. 2)

VOUT VS - VOUT





TJMAX - TAMAX





---------------------------------------------







- VS ISMAX





----------------------------------------------------------------------------------------------

(EQ. 3)

–

EL5146

+5V

VIN

+2.5V

VOUT

0.1µF

FIGURE 50. EL5146 AMPLIFIER IMPLEMENTED AS A

COMPARATOR

0.01

0.1

1.0

100

1000

OVERDRIVE (V)

POSITIVE GOING

SIGNAL

NEGATIVE GOING

SIGNAL

FIGURE 51. PROPAGATION DELAY vs OVERDRIVE FOR

AMPLIFIER USED AS A COMPARATOR

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