BU8874 Rohm Semiconductor, BU8874 Datasheet
BU8874
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BU8874 Summary of contents
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... The BU8874 and BU8874F are DTMF receiver ICs developed for use in telephone answering machines, and convert 16 different types of DTMF signals into 4-bit binary serial data. In addition to a compact 8-pin DIP (BU8874) package, these receivers feature a wide dynamic range, eliminating the need for an external input amplifier. Expertise from a num- ber of companies has been incorporated into these products to enable guard time control through a host microcontroller ...
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... Communication ICs FAbsolute maximum ratings (Ta=25_C) FRecommended operating conditions (Ta=25_C) FPin descriptions BU8874 / BU8874F 203 ...
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... Communication ICs FInput / output circuits INPUT OSC SD ESt 204 BU8874 / BU8874F PWDN ACK ...
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... Communication ICs FElectrical characteristics (unless otherwise noted, Ta=25_C, V BU8874 / BU8874F =5.0V) DD 205 ...
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... Any ACK pulses in excess of four are ig- nored until ESt goes HIGH again. Table 1 shows the for- mat of serial data output from the SD pin. 206 BU8874 / BU8874F (2) Power down interface The power down mode is activated by applying a rising edge at the PWDN pin when the ACK pin is LOW. The ACK pin may be taken from LOW to HIGH and back to LOW again while the circuit is in the power down mode ...
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... Communication ICs (3) Overall timing chart (4) Serial data correspondence table BU8874 / BU8874F (5) ACK and SD timing (6) Operation mode input logic 207 ...
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... If using a ceramic resonator, there may be problems with the precision of the oscillation frequency recommend using one of the ceramic resona- tors listed below. 208 BU8874 / BU8874F C502 : This is the V bypass capacitor, and is normally DD 100 F. JP501 : This is normally shorted. To test the current con- ...
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... HIGH level in the ESt guard time and the time constant is shown below. Figure 12 GH shows a timing diagram for guard times. BU8874 / BU8874F JP592 : If DTMF signals are being input directly, both ends should be shorted. Q591 Use these to increase the sensitivity of R591 X R595 the DTMF receiver ...
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... DTMF sequence received after the rising edge of the power supply. Therefore, input four dummy ACK pulses before the DTMF reception. FElectrical characteristic curves 210 BU8874 / BU8874F (2) Oscillation Oscillation frequency precision can be a problem with ce- ramic resonators. Before including a ceramic resonator in your design, please consult the resonator manufactur make sure this will not be a problem ...
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... Communication ICs FExternal dimensions (Units: mm) BU8874 / BU8874F 211 ...