BU8872FS-E2 Datasheet, PDF (7/10 Pages) Rohm – DTMF receiver for telephones BU8872 / BU8872FS

Communication ICs
BU8872 / BU8872FS
FOperation notes
(1) To prevent latch-ups, we recommend inserting a bypass capacitor (a capacitor between VDD and GND) close to
the VDD pin of the device.
(2) If using a pin-type ceramic resonator, connect a CH class capacitor between the OSCIN and OSCOUT pins and
the GND.
(3) This LSI is not equipped with the power-on reset function. Also, since the internal circuit (flip-flop circuit) becomes
unstable at the rising edge of the power supply, the internal circuit is initialized as shown below by the first DTMF se-
quence received after the rising edge of the power supply. Therefore, input four dummy ACK pulses before the DTMF
reception.
FSelecting attached components
(1) Power supply components
C502 : This is the VDD bypass capacitor, and is normally
100µF.
JP501 : This is normally shorted. To test the current con-
sumption of the IC, insert a DC ammeter in place
of JP501.
(2) Oscillation components
X501, C551, and C552 : Use a crystal or ceramic resona-
tor with an oscillation frequency of
4.194304MHz. If using a ceramic resonator,
there may be problems with the precision of the
oscillation frequency, so we recommend using
one of the ceramic resonators listed below.
X501
C551 C552
Murata CSA4.19MG
30pF 30pF
CST4.19MGW213 (internal capacitors)
Matsushita EFOEN4194
33pF 33pF
EFOEC4194
(internal capacitors)
TDK FCR4.19M5
33pF 33pF
FCR4.19MC5
(internal capacitors)
Kyocera KBR-4.19MSK 33pF 33pF
KBR-4.19MKS (internal capacitors)
Fujitsu FAR-C4j
(internal capacitors)
B-04194-K00
ROHM SFR3AU 4194 (internal capacitors)
C591 :
If you are using a dedicated resonator designed
for DTMF receivers, such as the X501, C551, or
C552, capacitor C591 should be left open. If you
are injecting an external clock, X501 should be
omitted and capacitor C591 used in its place.
Typically, this capacitor should be 47nF.
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