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SM8224 数据表(PDF) 9 Page - Nippon Precision Circuits Inc |
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SM8224 数据表(HTML) 9 Page - Nippon Precision Circuits Inc |
9 / 11 page SM8224B NIPPON PRECISION CIRCUITS—9 FUNCTIONAL DESCRIPTION The SM8224B receiver with caller ID service con- forms to the Bellcore standards. It incorporates FSK demodulator and dual-tone detection functions in a single chip. It has a dedicated dual-tone signal input so that the FSK signal input amplification and dual- tone signal input amplification can be set indepen- dently. This allows systems can be easily constructed that provide pre- and mid-conversation information services. FSK Demodulator Calling number identification service is sent as an FSK signal, and the SM8224B FSK demodulator processes this signal. The FSK signal conforms to the following Bellcore standard. Note: S1, S0, MODE setting should be used from above combination except Test mode. Dual Tone Detector When using mid-conversation information services, 2 mixed signals of 2130Hz and 2750Hz are sent on lines L1 and L2. The SM8224B detects the 2 signals from the background noise. It uses 2 separate high- order filters with center frequencies of 2130Hz and 2750Hz to detect the presence of the signal frequen- cies. In series with the filters are level detectors. When the input level exceeds the preset rating, the signal is detected. When the input level is below the rating, the signal is not detected. If both the 2130Hz and 2750Hz signals are simulta- neously detected, DTDET goes HIGH and starts charging the time constant circuit comprised by an external capacitor and external resistor. When the time constant circuit voltage rises above a fixed volt- age level, STR signal goes LOW to indicate dual tone detection. Table 1. FSK signal P arameter Description Modulation type Continuous-phase binar y frequency-shift- keying Logic “1” data (mark) 1200 ± 12 Hz Logic “0” data (space) 2200 ± 22 Hz Signal level (mark) −32 to −12 dBm Signal level (space) −36 to −12 dBm Data transfer rate 1200 ± 12 baud Table 2. Function select S 1 S 0 MODE Function S T R L O W L O W HIGH P ow er-dow n HIGH HIGH L O W L O W Dual-tone detection from DT1/DT21 L O W (dual tone confirmation) L O W HIGH L O W FSK and dual-tone detection from TIP/RING L O W (dual tone confirmation) HIGH HIGH L O W FSK detection from TIP/RING HIGH L O W L O W L O W Test mode2 1. DT1, DT2, DTQ are active in this mode only. 2. Test mode should not be used. |
类似零件编号 - SM8224 |
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类似说明 - SM8224 |
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