LA1867NM
3. FM muting on: Pin 33 (R33 = 100 kΩ)
The –3 dB limiting sensitivity can be changed by varying R33.
(Currently, R33 is 25 kΩ to set the –3 dB limiting sensitivity to 8 dBµ.)
4. FM muting attenuation adjustment: Pin 22 (R22 is a 30 or 50 kΩ variable resistor)
The pin 23 voltage is divided by the R22 variable resistor and input to pin 22. The no-input noise convergence is
determined by value of the pin 22 voltage.
(The LA1867NM has a noise convergence design target of from 5 dB to 30 dB.)
5. Muting time constant
The LA1867NM allows the volume level to be changed gradually for field variations during weak field reception by
setting the attack and recovery times for the soft mute function.
Attack time setting
ta = R23 * C22 = 940 µsec
Recovery time setting
tr = C22 * R23 = 23500 µsec
Unit (resistance: Ω, capacitance: F)
6. FM mute off function
The muting function is turned off if pin 22 is forcibly connected to ground.
No. 4619-19/32