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AD8324JRQ 数据表(PDF) 11 Page - Analog Devices |
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AD8324JRQ 数据表(HTML) 11 Page - Analog Devices |
11 / 16 page AD8324 Rev. A | Page 11 of 16 CLK SDATA DATEN TXEN GND VCC VCC ZIN = 150Ω VCC GND GND GND DATEN SDATA CLK GND TXEN RAMP BYP SLEEP NC GND AD8324-JRQ 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 1k Ω 174 Ω 1k Ω 1k Ω 1k Ω 1k Ω SLEEP TO DIPLEXER ZIN = 75Ω TOKO 458PT-1556 VIN+ VIN– VIN+ VIN– VOUT+ VOUT– 10 μF 0.1 μF 0.1 μF 1:1 0.1 μF 0.1 μF Figure 23. Typical Application Circuit Table 7. Adjacent Channel Power Adjacent Channel Symbol Rate (kSym/s) Channel Symbol Rate (kSym/s) 160 320 640 1280 2560 5120 160 –63 –64 –68 –71 –72 –66 320 –63 –64 –66 –70 –72 –67 640 –64 –64 –65 –67 –71 –67 1280 –67 –65 –65 –66 –68 –67 2560 –70 –67 –66 –66 –67 –65 5120 –72 –70 –67 –67 –64 –64 POWER SUPPLY The 3.3 V supply should be delivered to each of the VCC pins via a low impedance power bus. This ensures that each pin is at the same potential. The power bus should be decoupled to ground using a 10 μF tantalum capacitor located close to the AD8324. In addition to the 10 μF capacitor, VCC pins should be decoupled to ground with ceramic chip capacitors located close to the pins. The bypass pin, labeled BYP, should also be decoupled. The PCB should have a low impedance ground plane covering all unused portions of the board, except in areas of the board where input and output traces are in close proximity to the AD8324 and the output transformer. All AD8324 ground pins must be connected to the ground plane to ensure proper grounding of all internal nodes. SIGNAL INTEGRITY LAYOUT CONSIDERATIONS Careful attention to printed circuit board layout details will prevent problems due to board parasitics. Proper RF design techniques are mandatory. The differential input and output traces should be kept as short as possible. Keeping the traces short will minimize parasitic capacitance and inductance, which is most critical between the outputs of the AD8324 and the 1:1 output transformer. It is also critical that all differential signal paths be symmetrical in length and width. In addition, the input and output traces should be adequately spaced to minimize coupling (crosstalk) through the board. Following these guide-lines will optimize the overall performance of the AD8324 in all applications. INITIAL POWER-UP When the supply voltage is first applied to the AD8324, the gain of the amplifier is initially set to gain code 1. As power is first applied to the amplifier, the TXEN pin should be held low (Logic 0) to prevent forward signal transmission. After power has been applied to the amplifier, the gain can be set to the desired level by following the procedure provided in the Gain Programming for the AD8324 section. The TXEN pin can then be brought from Logic 0 to Logic 1, enabling forward signal transmission at the desired gain level. RAMP PIN AND BYP PIN FEATURES The RAMP pin (Pin 15) is used to control the length of the burst on and off transients. By default, leaving the RAMP pin unconnected will result in a transient that is fully compliant with DOCSIS 2.0 Section 6.2.21.2, Spurious Emissions During Burst On/Off Transients. DOCSIS requires that all between burst transients must be dissipated no faster than 2 μs. Adding capacitance to the RAMP pin will slow the dissipation even more. |
类似零件编号 - AD8324JRQ |
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类似说明 - AD8324JRQ |
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