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GS1504 bảng dữ liệu(PDF) 7 Page - Gennum Corporation |
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GS1504 bảng dữ liệu(HTML) 7 Page - Gennum Corporation |
7 / 13 page 522 - 05 - 05 7 of 13 Fig. 19 CLI Voltage vs. Belden 1694A Cable Length Fig. 20 CLI Voltage vs. Belden 8281 Cable Length DETAILED DESCRIPTION The GS1504 is a high speed bipolar IC designed to equalize HD serial digital data at a rate of 1.485Gb/s. The device can typically equalize greater than 100 meters of Belden 8281 cable or 150 meters of Belden 1694 cable. Powered from a single +5V or -5V power supply, the device consumes approximately 250mW of power The HD serial data signal may be connected to the input pins (SDI/SDI) in either a differential or single ended configuration. AC coupling of the inputs is recommended, as the SDI and SDI inputs are internally biased at approximately 2.7 volts. The input signal passes through a variable gain equalizing stage whose frequency response closely matches the inverse cable loss characteristic. In addition, the variation of the frequency response with control voltage imitates the variation of the inverse cable loss characteristic with cable length. The edge energy of the equalized signal is monitored by a detector circuit which produces an error signal corresponding to the difference between the desired edge energy and the actual edge energy. This error signal is integrated by an internal AGC filter capacitor providing a steady control voltage for the gain stage. As the frequency response of the gain stage is automatically varied by the application of negative feedback, the edge energy of the equalized signal is kept at a constant level which is representative of the original edge energy at the transmitter. The equalized signal is also DC restored, effectively restoring the logic threshold of the equalized signal to its correct level independent of shifts due to AC coupling. The digital output signals have a nominal voltage of 400mVpp differential, or 200mVpp single ended when terminated with 50 Ω as shown in Figure 21. Fig. 21 Typical Output Voltage Levels CABLE LENGTH INDICATION/CARRIER DETECT/MUTE The GS1504 incorporates a versatile analog cable length indicator (CLI) output and a programmable threshold output mute (MCLADJ). In addition, a multi-function CD/MUTE pin allows control of the GS1504 MUTE functionality. The voltage output of CLI pin is an approximation of the amount of cable present at the GS1504 input. The CLI voltage versus cable length (signal strength) is shown in Figures 19 and 20. With 0m of cable (800mV input signal levels), the CLI output voltage is approximately 3.3V. As the cable length increases, the CLI voltage decreases providing an approximate correlation between the CLI voltage and cable length. In applications where there are multiple input channels using the GS1504, it is advantageous to have a programmable mute output. The output of the GS1504 can be muted when the input signal decreases below a preselected input level. The voltage applied to the MCLADJ pin vs input cable length is shown in Figure 12. The MCLADJ pin may be left unconnected for applications where output muting is not required. This feature has been designed for use in applications such as routers where signal crosstalk and circuit noise cause the equalizer to output erroneous data when no input signal is present. The use of a Carrier Detect function with a fixed internal reference does not solve this problem since the signal to noise ratio on the circuit board 3.5 3 2.5 2 1.5 1 0.5 0 0 50 100 150 200 CABLE LENGTH (m) 3.5 3 2.5 2 1.5 1 0.5 0 0 50 100 150 CABLE LENGTH (m) 50 50 SDO SDO +100mV -100mV VCM = 4.0V typical +100mV -100mV VCM = 4.0V typical |
Số phần tương tự - GS1504_04 |
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Mô tả tương tự - GS1504_04 |
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