BU8872

Communication ICs DTMF receiver for telephones BU8872 / BU8872FS The BU8872 and BU8872FS 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 (BU8872) or 16-pin SSOP (BU8872FS) package, these receivers feature a wide dynamic range, eliminating the need for an external input amplifier. Expertise from a number of companies has been incorporated into these products to enable guard time control through a host microcomputer. FApplications Telephone answering machines FFeatures 1) Dynamic range of 45dB. (internal AGC) 2) 4-bit binary serial data output. 3) Guard time can be controlled through host microcomputer. 4) Input pins equipped with hysteresis. (ACK pin) FBlock diagram 5) 4.19MHz ceramic resonator or crystal resonator can be used. 6) 8-pin DIP package. (BU8872) 16-pin SSOP package. (BU8872FS) 192 Communication ICs FAbsolute maximum ratings (Ta=25_C) BU8872 / BU8872FS FRecommended operating conditions (Ta=25_C) 193 Communication ICs FElectrical characteristics DC characteristics (unless otherwise noted, Ta=25_C, VDD=5.0V) BU8872 / BU8872FS AC characteristics (unless otherwise noted, Ta=25_C, VDD=5.0V) 194 Communication ICs FPin descriptions BU8872 / BU8872FS FInput / output circuits 195 Communication ICs FCircuit operation A DTMF signal is supplied to the INPUT pin and applied to a pair of 6th-order bandpass filters, which separa...