BU8871F

Communication ICs DTMF receiver for telephones BU8871F The BU8871F is a DTMF receiver ICs developed for use in telephone answering machines, and converts 16 different types of DTMF signals into 4-bit binary serial data. It features 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 microcontroller. FBlock diagram 4) Input pins equipped with hysteresis. (ACK pin) 5) 4.19MHz crystal resonator can be used. 180 Communication ICs FAbsolute maximum ratings (Ta=25_C) BU8871F FRecommended operating conditions (Ta=25_C) FPin descriptions 181 Communication ICs FInput / output circuits BU8871F 182 Communication ICs FElectrical characteristics DC characteristics (unless otherwise noted, Ta=25_C, VDD=5.0V) BU8871F AC characteristics (unless otherwise noted, Ta=25_C, VDD=5.0V) 183 Communication ICs FMeasurement circuits BU8871F 184 Communication ICs FCircuit operation (1) An overview of operation A DTMF signal is supplied to the INPUT pin and applied to a pair of 6th-order bandpass filters, which separate the DTMF signal into its high (COL) and low (ROW) frequencies. The separated tones are converted into square waves and fed to a digital ...