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Datenblatt-Suchmaschine für elektronische Bauteile |
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Datenblatt-Suchmaschine für elektronische Bauteile |
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CPC5604 Datenblatt(PDF) 17 Page - Clare, Inc. |
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CPC5604 Datenblatt(HTML) 17 Page - Clare, Inc. |
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17 / 33 page  CPC5604 www.clare.com 17 XXX Ring Signal Detection The snoop circuit actively monitors the telephone line for 2 conditions: 1. Incoming ring signal 2. Caller ID information The Snoop circuit “snoops” the line continuously while the LiteLinkTM is in the on-hook mode. Current taken from the telephone line in the on-hook condition by the LITELINKTM is maintained at a low 2uA maximum thus meeting regulatory requirements for minimum on-hook impedance limitation. When the central office places the ring signal on the telephone line, that signal is cou- pled through a pair of RC circuits to a differential ampli- fier in the LiteLinkTM. Referring to Block Diagram, snoop capacitors connect- ed to the SNP1/SNP2 pins provide a high voltage isola- tion barrier between the host and the telephone line while coupling the AC signals to the snoop amplifier. The ring signal is digitized and brought out to the RING pin where the host can qualify it as a valid ring signal. The ring detection threshold is dependent on the values of 3 external components: RRXF (R3), RSNOOP (R5 or R6), and CS (C6 or C7). The default values in the typi- cal bill of materials reflects the parameters in the data sheet for typical operation. If it is desired to change the threshold, the values can be selected by using the equation: Where f = ring frequency typically 20Hz. = 330E-3 (R SNOOP) 2 + 1 5R RXF (2 πf C S) 2 VRING(PEAK) TXA1 TXA2 - + 0.1uf 0.1uf HOST DATA PUMP/CODEC SINGLE ENDED CONNECTION TO CPC5604A CPC5604A LITELINK TM TX- TX+ Figure 2D Connection To Host Single Ended (Transmit) Care should be taken when using this equation since RRXF (R3), CS (C6 or C7), and RSNOOP (R5 or R6) affect receive gain and Caller ID gain. It is recom- mended that RRXF (R3) be set to the typical value and then after adjusting the ring detect threshold, check that CID gain is acceptable. Caller ID Detection Caller ID (CID) is a service offered by the telephone company to provide caller information (i.e. caller’s tele- phone number) to the called party. CID service is optional and signals only appear on the telephone lines of subscribers that pay for this feature. The CID infor- mation appears on the telephone line after the first ring burst is sent from the central office (CO). Some of the characteristics of the CID signal are sum- marized below: Parameter Value Signal Level -13dBm Link Type Simplex, 2W Transmission Scheme Phase-coherent, FSK Logical 1 (mark) 1200±12Hz Logical 0 (Space) 2200± 22Hz Transmission Rate 1200bps Data serial binary async BER < 10E -5 Bit Duration 833±50uS (same for start/stop as well) Full details about the CID signal can be found in Bellcore document TR-TSY-000030, issue 1/1988. Figure 2.7.A shows the CID timing diagram. Waveform #1 represents the Analog signals on the telephone line (amplitude not drawn to scale), waveform #2 is the dig- ital RING detect output from the LiteLinkTM, waveform #3 is the CID input to the LiteLinkTM from the Host. After the first ring burst is detected by the host, the host enables the CID line which automatically couples the snoop circuit to the RX outputs on the LiteLinkTM. |
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