Communication ICs Speech network for telephones BA6569AS / BA6569AFP The BA6569AS and BA6569AFP are speech networks which possesses the basic functions required for handset communications. In addition to amplifying signals from a transmitter and sending them to a telephone line, they also amplify only reception signals from a telephone line and drive the receiver. In addition to a function which compensates for fluctuation in the transmission and reception volume caused by the length of the telephone line (AGC), they are also equipped with a manual PAD function in order to accommodate PBX. FApplications Telephones and telephone equipment FFeatures 1) Basic speech network functions built in. 2) Single output pin of reception pre-amplifier is separate. 3) Single input pin of reception pre-amplifier is separate, enabling mixing of input. 4) Input to microphone pre-amplifier is balanced and offers high resistance to in-line noise. 5) Input pin of MF pre-amplifier enables mixing of input. 6) Manual pad pin included. 7) Pre-amplifiers for reception, microphone, and MF employ AGC based on telephone line current. FAbsolute maximum ratings (Ta = 25_C) 226 8) AC impedance can be raised by altering the positive feedback. This enables configuration of power supply circuits for microcomputers and other applications using only a single resistor. 9) A BTL circuit is used for reception output, and the wide dynamic range enables both dynamic and ceramic receivers to be accommodated. 10) Few external attachments are required. 11) 22-pin SDIP and 24-pin HSOP packages available. Communication ICs BA6569AS / BA6569AFP Block diagram 227 Communication ICs BA6569AS / BA6569AFP FElectrical characteristics (unless otherwise noted, Ta = 25_C, f = 1kHz, BPF = 400Hz to 30kHz) 228 Communication ICs BA6569AS / BA6569AFP Electrical characteristic curves 229 Communication ICs 230 BA6569AS / BA6569AFP Communication ICs BA6569AS / BA6569AFP Measurement circuits 231 Communication ICs Circuit operation The BA6569AS and BA6569AFP carry out the following basic operations. (1) Handset talk and receive Voice signals received from a telephone line are output to a handset speaker. Voice signals from the handset microphone are also output to the telephone line. (2) DTMF send and key tone input The BA6569AS and BA6569AFP have a mute switch which can be switched between a “handset send and receive” mode and a “DTMF send and key tone input” mode by an external logic signal. In the “DTMF send and key tone input” mode, it transmits DTMF signals from the dial pad to the telephone line, and key tones to the handset receiver. 232 BA6569AS / BA6569AFP (3) AGC Gain is adjusted steplessly in response to the size of current from the telephone line. When there is a large current (a short distance is involved), the gain is lowered. The gain volume can also be adjusted by changing the value of the resistor connected to the AGC pin. (4) Manual pad In order to accommodate situations such as a PBX, where there is little current but a short distance is involved, the gain can be lowered by a constant volume regardless of the current value. Fluctuation in the amount of gain can be adjusted by changing the value connected to the MPAD pin. Communication ICs BA6569AS / BA6569AFP Pin descriptions 233 Communication ICs Operation notes The maximum power dissipation for the BA6569AS is 1100mW, and for the BA6569AFP, the maximum power dissipation is 1200mW (when mounted on 90mm 50mm 1.6mm glass epoxy boards, however, fins should be soldered to the foil pattern). Since the maximum power dissipation varies with temperature, the product of the applied voltage VL and the total current drawn by the IC, after factoring in the temperature, should not exceed the maximum dissipation. 234 BA6569AS / BA6569AFP Communication ICs BA6569AS / BA6569AFP Application example 235 Communication ICs Application board pattern 236 BA6569AS / BA6569AFP Communication ICs BA6569AS / BA6569AFP Application board component layout External dimensions (Units: mm) 237