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ISL28191 数据表(PDF) 9 Page - Intersil Corporation |
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ISL28191 数据表(HTML) 9 Page - Intersil Corporation |
9 / 14 page 9 FN6156.2 Applications Information Product Description The ISL28191 and ISL28291 are voltage feedback operational amplifier designed for communication and imaging applications requiring very low voltage and current noise. Both parts feature low distortion while drawing moderately low supply current. The ISL28191 and ISL28291 use a classical voltage-feedback topology which allows them to be used in a variety of applications where current-feedback amplifiers are not appropriate because of restrictions placed upon the feedback element used with the amplifier. Enable/Power-Down The ISL28191 and ISL28291 amplifiers are disabled by applying a voltage greater than 2V to the ENABLE pin, with respect to the V- pin. In this condition, the output(s) will be in a high impedance state and the amplifier(s) current will be reduced to 13µA/Amp. By disabling the part, multiple parts can be connected together as a MUX. The outputs are tied together in parallel and a channel can be selected by the ENABLE pin. The ENABLE pin also has an internal pull down. If left open, the ENABLE pin will pull to the negative rail and the device will be enabled by default. Input Protection All input terminals have internal ESD protection diodes to both positive and negative supply rails, limiting the input voltage to within one diode beyond the supply rails. Both parts have additional back-to-back diodes across the input terminals (as shown in Figure 25). In pulse applications where the input Slew Rate exceeds the Slew Rate of the amplifier, the possibility exists for the input protection diodes to become forward biased. This can cause excessive input current and distortion at the outputs. If overdriving the inputs is necessary, the external input current must never exceed 5mA. An external series resistor may be used to limit the current as shown in Figure 25. Using Only One Channel The ISL28291 is a Dual channel op-amp. If the application only requires one channel when using the ISL28291, the user must configure the unused channel to prevent it from oscillating. Oscillation can occur if the input and output pins are floating. This will result in higher than expected supply currents and possible noise injection into the channel being used. The proper way to prevent this oscillation is to short the output to the negative input and ground the positive input (as shown in Figure 26). Current Limiting The ISL28191 and ISL28291 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. This is why output short circuit current is specified and tested with RL = 10Ω. Power Dissipation It is possible to exceed the +125°C maximum junction temperatures under certain load and power-supply conditions. It is therefore important to calculate the maximum junction temperature (TJMAX) for all applications to determine if power supply voltages, load conditions, or package type need to be modified to remain in the safe operating area. These parameters are related as follows: where: •PDMAXTOTAL is the sum of the maximum power dissipation of each amplifier in the package (PDMAX) •PDMAX for each amplifier can be calculated as follows: where: •TMAX = Maximum ambient temperature • θJA = Thermal resistance of the package •PDMAX = Maximum power dissipation of 1 amplifier •VS = Supply voltage •IMAX = Maximum supply current of 1 amplifier •VOUTMAX = Maximum output voltage swing of the application •RL = Load resistance FIGURE 25. LIMITING THE INPUT CURRENT TO LESS THAN 5mA - + R FIGURE 26. PREVENTING OSCILLATIONS IN UNUSED CHANNELS - + T JMAX T MAX θ JAxPDMAXTOTAL () + = PD MAX 2*V S I SMAX V S ( - V OUTMAX ) V OUTMAX R L ---------------------------- × + × = ISL28191, ISL28291 |
类似零件编号 - ISL28191 |
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类似说明 - ISL28191 |
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