5108IS Просмотр технического описания (PDF) - Renesas Electronics
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5108IS Datasheet PDF : 13 Pages
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EL5108, EL5308
325
IN- 325
-
+
IN+
FIGURE 23. AV = +1
Supply Voltage Range and Single-Supply Operation
The EL5108 and EL5308 have been designed to operate with
supply voltages having a span of greater than or equal to 5V
and less than 12V. In practical terms, this means that they will
operate on dual supplies ranging from ±2.5V to ±5V. With
single-supply, they will operate from 5V to 10V.
As supply voltages continue to decrease, it becomes
necessary to provide input and output voltage ranges that can
get as close as possible to the supply voltages. The EL5108
and EL5308 have an input range which extends to within 2V of
either supply. So, for example, on ±5V supplies, the input
range is about ±3V. The output range is also quite large,
extending to within 1V of the supply rail. On a ±5V supply, the
output is therefore capable of swinging from -4V to +4V.
Single-supply output range is larger because of the increased
negative swing due to the external pull-down resistor to
ground. Figure 24 shows an AC-coupled, gain of +2, +5V
single supply circuit configuration.
325
+5
0.1µF
VIN
325
-
+5
+
1k
0.1µF
1k
4.7µF
VOUT
FIGURE 24.
Video Performance
For good video performance, an amplifier is required to
maintain the same output impedance and the same frequency
response as DC levels are changed at the output. This is
especially difficult when driving a standard video load of 150,
because of the change in output current with DC level.
Previously, good differential gain could only be achieved by
running high idle currents through the output transistors (to
reduce variations in output impedance). Special circuitry has
been incorporated in the EL5108 and EL5308 to reduce the
variation of output impedance with current output. This results
in dG and dP specifications of 0.01% and 0.01°, while driving
150 at a gain of 2.
Output Drive Capability
In spite of its low 3.5mA of supply current per amplifier, the
EL5108 and EL5308 are capable of providing a maximum of
±130mA of output current.
Driving Cables and Capacitive Loads
When used as a cable driver, double termination is always
recommended for reflection-free performance. For those
applications, the back-termination series resistor will decouple
the EL5108 and EL5308 from the cable and allow extensive
capacitive drive. However, other applications may have high
capacitive loads without a back-termination resistor. In these
applications, a small series resistor (usually between 5 and
50) can be placed in series with the output to eliminate most
peaking.
Current Limiting
The EL5108 and EL5308 have no internal current-limiting
circuitry. If the output is shorted, it is possible to exceed the
Absolute Maximum Rating for output current or power
dissipation, potentially resulting in the destruction of the
device.
Power Dissipation
With the high output drive capability of the EL5108 and
EL5308, it is possible to exceed the +125°C Absolute
Maximum junction temperature under certain very high load
current conditions. Generally speaking when RL falls below
about 25, it is important to calculate the maximum junction
temperature (TJMAX) for the application to determine if power
supply voltages, load conditions, or package type need to be
modified for the EL5108 and EL5308 to remain in the safe
operating area. These parameters are calculated as follows:
TJMAX = TMAX + JA n PDMAX
where:
TMAX = Maximum ambient temperature
JA = Thermal resistance of the package
n = Number of amplifiers in the package
PDMAX = Maximum power dissipation of each amplifier in
the package
PDMAX for each amplifier can be calculated as follows:
PDMAX = 2 VS ISMAX + VS - VOUTMAX V-----O----U--R--T---L-M-----A----X--
where:
VS = Supply voltage
ISMAX = Maximum supply current of 1A
VOUTMAX = Maximum output voltage (required)
RL = Load resistance
FN7358 Rev 8.00
August 11, 2015
Page 9 of 13
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