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EL5370 Datasheet(PDF) 10 Page - Intersil Corporation |
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EL5370 Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 15 page 10 FN7309.7 May 7, 2007 Differential and Common Mode Gain Settings As shown at the simplified schematic, since the feedback resistors RF and the gain resistor are integrated with 200 Ω and 400 Ω, the EL5170 and EL5370 have a fixed gain of 2. The common mode gain is always one. Driving Capacitive Loads and Cables The EL5170 and EL5370 can drive 75pF differential capacitor in parallel with 200 Ω differential load with less than 3.5dB of peaking. If less peaking is desired in applications, a small series resistor (usually between 5 Ω to 50Ω) can be placed in series with each output to eliminate most peaking. However, this will reduce the gain slightly. When used as a cable driver, double termination is always recommended for reflection-free performance. For those applications, a back-termination series resistor at the amplifier’s output will isolate the amplifier from the cable and allow extensive capacitive drive. However, other applications may have high capacitive loads without a back-termination resistor. Again, a small series resistor at the output can help to reduce peaking. Disable/Power-Down The EL5170 and EL5370 can be disabled and placed their outputs in a high impedance state. The turn off time is about 1µs and the turn on time is about 200ns. When disabled, the amplifier’s supply current is reduced to 2µA for IS+ and 120µA for IS- typically, thereby effectively eliminating the power consumption. The amplifier’s power down can be controlled by standard CMOS signal levels at the ENABLE pin. The applied logic signal is relative to VS+ pin. Letting the EN pin float or applying a signal that is less than 1.5V below VS+ will enable the amplifier. The amplifier will be disabled when the signal at EN pin is above VS+ -0.5V. Output Drive Capability The EL5170 and EL5370 have internal short circuit protection. Its typical short circuit current is ±80mA. If the 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 ±60mA. This limit is set by the design of the internal metal interconnect. Power Dissipation With the high output drive capability of the EL5170 and EL5370 it is possible to exceed the 125°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 the load conditions or package types need to be modified for the amplifier to remain in the safe operating area. The maximum power dissipation allowed in a package is determined according to: Where: TJMAX = Maximum junction temperature TAMAX = Maximum ambient temperature θ JA = Thermal resistance of 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: Where: VS = Total supply voltage ISMAX = Maximum quiescent supply current per channel ΔVO = Maximum differential output voltage of the application RLD = Differential load resistance ILOAD = Load current i = Number of channels By setting the two PDMAX equations equal to each other, we can solve the output current and RLOAD to avoid the device overheat. Power Supply Bypassing and Printed Circuit Board Layout As with any high frequency device, a good printed circuit board layout is necessary for optimum performance. Lead lengths should be as sort as possible. The power supply pin must be well bypassed to reduce the risk of oscillation. For normal single supply operation, where the VS- pin is connected to the ground plane, a single 4.7µF tantalum capacitor in parallel with a 0.1µF ceramic capacitor from VS+ to GND will suffice. This same capacitor combination should be placed at each supply pin to ground if split supplies are to be used. In this case, the VS- pin becomes the negative supply rail. For good AC performance, parasitic capacitance should be kept to minimum. Use of wire wound resistors should be avoided because of their additional series inductance. Use of sockets should also be avoided if possible. Sockets add parasitic inductance and capacitance that can result in compromised performance. Minimizing parasitic capacitance at the amplifier’s inverting input pin is very important. The feedback resistor should be placed very close to the inverting input pin. Strip line design techniques are recommended for the signal traces. PD MAX T JMAX T AMAX – Θ JA --------------------------------------------- = PD i V S I SMAX V S ΔV O R LD ------------ × + × ⎝⎠ ⎜⎟ ⎛⎞ × = EL5170, EL5370 |
Similar Part No. - EL5370 |
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Similar Description - EL5370 |
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