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ISL28291FBZ-T7 Datenblatt(PDF) 10 Page - Intersil Corporation |
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ISL28291FBZ-T7 Datenblatt(HTML) 10 Page - Intersil Corporation |
10 / 16 page 10 FN6156.7 August 11, 2008 Applications Information Product Description The ISL28191 and ISL28291 are voltage feedback operational amplifiers designed for communication and imaging applications requiring low distortion, very low voltage and current noise. Both parts feature high bandwidth while drawing moderately low supply current. They 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 EN 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 EN pin. The EN pin also has an internal pull-down. If left open, the EN 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 29). 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 29. 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 30). Power Supply Bypassing and Printed Circuit Board Layout As with any high frequency device, good printed circuit board layout is necessary for optimum performance. Low impedance ground plane construction is essential. Surface mount components are recommended, but if leaded components are used, lead lengths should be as short as possible. The power supply pins must be well bypassed to 11 1 (A) 7 (B) 1 (A) 9 (B) 10 (A) 8 (B) OUT OUT_A OUT_B Output Circuit 2 6 6 8 10 9 V+ Positive supply 55 N/A 5 (A) 6 (B) 4 (A) 5 (B) EN EN_A EN_B Enable BAR pin internal pull-down; Logic “1” selects the disabled state; Logic “0” selects the enabled state. Circuit 3 Pin Descriptions (Continued) ISL28191 (6 Ld SOT-23) ISL28191 (6 Ld µTDFN) ISL28291 (8 Ld SOIC) ISL28291 (10 Ld MSOP) ISL28291 (10 Ld µTQFN) PIN NAME FUNCTION EQUIVALENT CIRCUIT V+ V- OUT EN V+ V- FIGURE 29. LIMITING THE INPUT CURRENT TO LESS THAN 5mA - + R FIGURE 30. PREVENTING OSCILLATIONS IN UNUSED CHANNELS - + ISL28191, ISL28291 |
Ähnliche Teilenummer - ISL28291FBZ-T7 |
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Ähnliche Beschreibung - ISL28291FBZ-T7 |
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