BU8871F Datasheet, PDF (8/12 Pages) Rohm – DTMF receiver for telephones

Communication ICs
FSelecting attached components
(1) Power supply components
(2) Oscillation components
(3) DTMF input
BU8871F
C502 : This is the VDD bypass capacitor, and is normally
100µF. The maximum recommended operating
power supply voltage is 5.25V, so a voltage
withstand value of 6.3V is sufficient.
JP501 : This is normally shorted. To test the current con-
sumption of the IC, insert a DC ammeter in place
of JP501.
X501 :
C591 :
Use a crystal or ceramic resonator with an os-
cillation frequency of 4.194304MHz. If using a
ceramic resonator, there may be problems with
the precision of the oscillation frequency, so
please consult the manufacturer of the resona-
tor to make sure problems will not occur.
If you are using the X501 dedicated resonator
designed for DTMF receivers, capacitor C591
should be left open.
If you are injecting an external clock, X501
should be omitted and DC blocking capacitor
C591 used in its place. Typically, this capacitor
should be 47nF.
C501 :
This is the DC blocking capacitor. Select a ca-
pacitor that will pass DTMF signals (greater
than 697Hz) without significantly attenuating
the signals.
JP592 : If DTMF signals are being input directly, both
ends should be shorted.
Q591
R591 X R595 ^{Use these to increase the sensitivity of}
C592, C593 ^{the DTMF receiver.}
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