EL5246CSZ Просмотр технического описания (PDF) - Renesas Electronics
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EL5246CSZ Datasheet PDF : 24 Pages
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EL5144, EL5146, EL5244, EL5246, EL5444
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:
PDMAX = N VS ISMAX + VS - VOUT V-----OR----UL----T--
(EQ. 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:
RL
=
-------------------V----O-----U----T------------V----S-----------V----O----U-----T----------------------
T----J---M-----A-N---X-----------T-J---AA----M----A----X--
-
VS ISMAX
(EQ. 3)
Assuming worst case conditions of TA = +85C, VOUT = VS/2V,
VS = 5.5V, and ISMAX = 8.8mA per amplifier, following is a table
of all packages and the minimum RL allowed.
PART
EL5144CW
EL5146CS
EL5146CN
EL5244CS
EL5244CN
EL5244CY
EL5246CY
EL5246CS
EL5246CN
EL5444CU
EL5444CS
EL5444CN
PACKAGE
SOT23-5
SOIC-8
PDIP-8
SOIC-8
PDIP-8
MSOP-8
MSOP-10
SOIC-14
PDIP-14
QSOP-16
SOIC-14
PDIP-14
MINIMUM RL
37
21
14
48
30
69
69
34
23
139
85
51
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.
1
8
EL5146
VIN
+
–
2
-
7
+2.5V
3
+
6
4
5
+5V
0.1µF
VOUT
RL
FIGURE 50. EL5146 AMPLIFIER IMPLEMENTED AS A
COMPARATOR
1000
NEGATIVE GOING
SIGNAL
100
POSITIVE GOING
SIGNAL
10
0.01
0.1
1.0
OVERDRIVE (V)
FIGURE 51. PROPAGATION DELAY vs OVERDRIVE FOR
AMPLIFIER USED AS A 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.
FN7177 Rev 2.00
March 31, 2011
Page 18 of 24
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