1997 May 26

9

Philips Semiconductors

Product specification

Low power PLL FM demodulator for

satellite TV receivers

TDA8012AM

13. For applications in which a fixed AGC threshold is used, it is recommended to use the internal resistor voltage divider

for lower AGC threshold spread. In this case, the threshold is set to 57 dB

µV.

14. In the application circuit (see Fig.4) the voltage at the AGC output decreases when the IF input level increases above

the adjusted AGC threshold.

15. The outputs from the AFC and carrier detector are combined at pin 19 (see Fig.3). During search tuning, when the

input frequency is outside the capture range, the combined output (carrier detector function) is at a LOW level

in Fig.3, the voltage at pin 19 is now a function of the centre frequency (AFC function). This information may be read

16. This current discharges the external capacitors between two energy dispersal peak values and avoid the use of

external resistors in parallel with capacitors.

17. The drift of the automatic frequency control voltage is measured in accordance with the following method:

pin 20 must be adjusted to obtain a 1.5 V output at the AFC output (pin 19).

(without input signal). The drift of the automatic frequency control voltage will then be equal to the difference

Fig.3 AFC and carrier detector output.

handbook, full pagewidth

MBH932

0

frequency

0.15

0.3

0.45

0.6

0.8

1

AFC DATA

V19

VCC

carrier detect on

f o

500 kHz