BA6569AS Datasheet, PDF (7/12 Pages) Rohm – Speech network for telephones

Communication ICs
BA6569AS / BA6569AFP
FCircuit 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 mi-
crophone 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 re-
ceive” 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 hand-
set receiver.
(3) AGC
Gain is adjusted steplessly in response to the size of cur-
rent from the telephone line. When there is a large cur-
rent (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 in-
volved, the gain can be lowered by a constant volume re-
gardless of the current value. Fluctuation in the amount
of gain can be adjusted by changing the value connected
to the MPAD pin.
232