LA75503V
Continued from preceding page.
Pin No.
Pin
16
AFT OUT
Pin Function
Pin 16 is the AFT output pin.
Use external resistors of 47 kΩ and a filter
capacitance 0.1 µF.
The AFT circuit generates the AFT voltage by
comparing the signal obtained by dividing the
4-MHz reference frequency with the signal obtained
by dividing VCO.
Since it uses a digital phase comparator, a dead
zone exists in the AFT center.
waveform
Internal Circuit
Pin 17 is the RF AGC output.
RF AGC max is determined by R1 and R2.
RF AGC min is determined by R3 and R4.
Capacitor C1 prevents oscillation and capacitor C2 Comparator
17
RF AGC OUT
is the RF AGC filter.
Normally 30 kΩ is used for R1, but if the tuner's F/E
transistor is GaAS, the gate's impedance is lower,
so use approx. 10 kΩ.
Pin 18 is the IF AGC filter pin.
Normally, 0.01 µF to 0.02 µF polyester film
18
IF AGC FILTER
capacitor is used.
Determine the impedance based on H-SAG and
AGC speed.
19
NC
Not connected
Continued on next page.
No. 6804-9/15