TDA7529_11 Datasheet, PDF (15/61 Pages) STMicroelectronics – RF front-end for AM/FM DSP car-radio with IF sampling

TDA7529
Function description
3.7
VCO
The 3.7 GHz VCO has an internal switch that allows extending the oscillation frequency
range. This is required by the fact that each of the two resulting VCO sub-bands
(upper/lower) cannot individually cover the complete required frequency range versus
temperature and process; for this reason a calibration procedure is needed to determine the
process type (typical, slow, fast) and select the transition frequency between the two VCO
sub-bands.
To run the procedure the VCO range 2 must be selected, the synthesized frequency needs
to be set to 4GHz; then if Vtuning > 2.6V then the process is 'slow', if Vtuning < 1.7V then is
'fast' and otherwise is 'typical'. The switching frequency as a function of the process is
reported in the following table:
Table 4. Switching frequency as a function of the process
Slow
Typ.
3.635 GHz
3.72 GHz
Fast
3.794 GHz
3.8
FREF
The reference frequency for the PLL can be derived by a XTAL directly connected to the
device or by means of an LVDS signal. In the latter case an external matching resistor must
be used to obtain the desired input signal level.
3.9
A/D converter
The front-end contains a 6 bit SAR A/D-converter for sensing several analog values of the
tuner. The following analog sources can be switched to the ADC input by software
command:
● FM RF AGC capacitor voltage
● AM RF AGC capacitor voltage
● IF AGC capacitor voltage (automatically connected to the FM or AM IF AGC filtering
capacitor)
● PLL tuning voltage
● Temperature sensor
● GPIO 1 voltage
● GPIO 2 voltage
● ADC reference generated from VCC.
The ADC can be clocked by an integrated RC-oscillator, in which case the oscillation
frequency is programmable, or by the PLL reference frequency.
Doc ID 13311 Rev 4
15/61