L6726
LINEAR INTEGRATED CIRCUIT
APPLICATION INFORMATION(Cont.)
R15:
This resistor is used to set the driving capability of the receiver output amplifier. Common values are 0 Ω to 50 Ω.
Setting it for low driving capability results in function at lower line current. Breaking up pin 16 will give lower power
consumption and total mute of the receiver when muting the circuit. Disconnecting pin 15 will of cause also give total
receiver mute.
D1, D2, D3, D4, D5:
Rectifier bridge and over voltage protector. The zener voltage at D5 should be as low as possible. Common values
are between 12V~16V.
RDC1, RDC2:
Refer to fig. 5
The pre-set output voltage of 2.35V can easily, if needed, be changed to another value by applying one or two
resistor(RDC1,RDC2) in parallel with the internal resistors (each 15kΩ+/-20%).It is possible to get a rather high voltage
and current from the DC-supply as long as the high current and voltage is available from the line. The DC voltage
has to be filtered by a capacitor and this can, at high DC-voltage and low line current, interfere with the signal on the
line and cause distortion. You can minimize the interference, with a resistor in series with the filter capacitor. The DC
voltage will, of course, be more dependent of the DC-supply current. The DC-output pin has a very low input leak
current, to allow stand-by feeding of the dialer. It is also possible to use pin 9 to feed microphones etc. that do not
need stand-by feeding, without interfering with the stand-by feeding on pin 8. Note that a high current consumption
by the external device will alter the DC characteristics of the speech circuit
UNISONIC TECHNOLOGIES CO., LTD
9 of 13
QW-R108-015, C
www.unisonic.com.tw
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