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ISL1539IRZ-T7 数据表(PDF) 9 Page - Intersil Corporation |
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ISL1539IRZ-T7 数据表(HTML) 9 Page - Intersil Corporation |
9 / 11 page ISL1539 9 FN7516.4 June 21, 2013 Application Information The ISL1539 consists of two sets of high-power line driver amplifiers that can be connected for full duplex differential line transmission. The amplifiers are designed to be used with signals up to 30MHz and produce low distortion levels. A typical interface circuit is shown in Figure 20. The amplifiers are wired with one in positive gain and the other in a negative gain configuration to generate a differential output for a single-ended input. They will exhibit very similar frequency responses for gains of three or greater and thus generate very small common-mode outputs over frequency, but for low gains the two drivers RF's need to be adjusted to give similar frequency responses. The positive-gain driver will generally exhibit more bandwidth and peaking than the negative-gain driver. If a differential signal is available to the drive amplifiers, they may be wired so: Each amplifier has identical positive gain connections, and optimum common-mode rejection occurs. Further, DC input errors are duplicated and create common-mode rather than differential line errors. Power Supplies and Dissipation Due to the high power drive capability of the ISL1539, much attention needs to be paid to power dissipation. The power that needs to be dissipated in the ISL1539 has two main contributors. The first is the quiescent current dissipation. The second is the dissipation of the output stage. The quiescent power in the ISL1539 is not constant with varying outputs. In reality, 7mA of the 15mA needed to power the drivers is converted in to output current. Therefore, in the equation below we should subtract the average output current, IO, or 7mA, whichever is the lowest. We’ll call this term IX. Therefore, we can determine a quiescent current with Equation 1: where: •VS is the supply voltage (VS+ to VS-) •IS is the maximum quiescent supply current (IS+ + IS-) •IX is the lesser of IO or 7mA (generally IX = 7mA) The dissipation in the output stage has two main contributors. Firstly, we have the average voltage drop across the output transistor and secondly, the average output current. For minimal power dissipation, the user should select the supply voltage and the line transformer ratio accordingly. The supply voltage should be kept as low as possible, while the transformer ratio should be selected so that the peak voltage required from the ISL1539 is close to the maximum available output swing. There is a trade off, however, with the selection of transformer ratio. As the ratio is increased, the receive signal available to the receivers is reduced. Once the user has selected the transformer ratio, the dissipation in the output stages can be selected with Equation 2: where: •VS is the supply voltage (VS+ to VS-) •VO is the average output voltage per channel •IO is the average output current per channel The overall power dissipation (PDISS) is obtained by adding PDquiescent and PDtransistor. Then, the θJA requirement needs to be calculated. This is done using Equation 3: FIGURE 20. TYPICAL LINE INTERFACE CONNECTION FIGURE 21. DRIVERS WIRED FOR DIFFERENTIAL INPUT + + - - - + + - ROUT RG R RF RF RF RIN R RF RIN LINE - ZLINE LINE + ROUT DRIVER INPUT RECEVIE OUT+ RECEVIE OUT- RECEVIE AMPLIFIERS + - RF RF 2RG - + - P Dquiescent V S I S 2I X – () × = (EQ. 1) P Dtransistors 2I O V S 2 ------- ⎝ ⎛ × × V O – ⎠ ⎞ = (EQ. 2) θ JA T JUNCT T AMB – () P DISS ------------------------------------------------- = (EQ. 3) |
类似零件编号 - ISL1539IRZ-T7 |
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类似说明 - ISL1539IRZ-T7 |
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