LA1140
Proper cares in using LA1140
1)
The detector transformers should be designed to develop a quadrature signal (pin 11) of higher than 175 mVrms
(approximately 105 dBµ) under high antenna signal input. If the quadrature signal strength is less than 125 mVrms, the
muting drive output (V14) cannot decrease to zero even in a strong signal strength. Furthermore, when the quadrature signal
strength lies between 125 mV and 175 mV, the muting drive output may move from zero to plus under high temperature
conditions.
When designing a PC board, special care should be given to the ground pattern layout by referring to that of the recommend
PC board example as shown below.
Do not connect a capacitor directly between pin 16 and ground. If the signal intensity of IF input varies in the vicinity of
90 dBµ, the voltage at pin 16 varies. Thus, charging/discharging current flows into the capacitor and goes to the muting drive
output (pin 14) through the inverter inside the IC, thereby causing the muting to malfunction.
2)
3)
Sample Application Circuit 1
TOKO
Front end
higher
[Maximum Att. Adj.]
lower
[Muting ON level Adj.]
Unit (resistance:
Ω,
capacitance: F)
[Slope Adj.]
[Slope Adj.]
No. 729-9/15
SANYO [ SANYO SEMICON DEVICE ]
