LA8518NM Datasheet, PDF (22/31 Pages) Sanyo Semicon Device – Signal Processor for Cordless Telephone Base Sets

LA8518NM
c LINE amplifier attenuator
Normally, the attenuator is set to 0 dB. It is set to −6 dB when serial data 3 dB is on.
Crosspoint switch
c REC amplifier V/I conversion
PB input
V_IN = 0.3 V_P-P
PRE Amp output level
Internal reference voltage 2.3 V
In order to derive the recording current for the DC bias, this circuit performs V/I conversion. The conversion gain and the bias
current can be controlled by the external resistor connected to pin 20. Current equal to the current output from pin 20 is output
from pin 22.
DC bias current = 2.3 V/(100 Ω + 15 kΩ) 6 150 µA
Signal current = 1.0 Vp-p/(100 Ω + 15 kΩ//22 kΩ) 6 110 µAp-p
c VOX
1 The VOX circuit determines whether or not conversation is taking place. If the VOX input (pin 36) signal is −24dB or
higher, the VOX output (pin 45) goes low. The output level is adjusted by inserting a resistor between VOX TH (pin 32)
and V_REF (pin 30).
2 Because the circuit can be used as a waveform shaper by connecting VOX C (pin 37) to V_CC (setting pin 37 high), a
400 Hz beep tone can be detected.
(Open collector output)
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