TDA5211 Datasheet, PDF (18/52 Pages) Infineon Technologies AG – ASK/FSK Single Conversion Receiver

TDA 5211
Functional Description
mined by connecting a capacitor to the TAGC pin (Pin 4) and should be chosen
along with the appropriate threshold voltage according to the intended operat-
ing case and interference scenario to be expected during operation. The opti-
mum choice of AGC time constant and the threshold voltage is described in
Section 4.1.
3.4.2 Mixer
The Double Balanced Mixer downconverts the input frequency (RF) in the
range of 310-350MHz to the intermediate frequency (IF) at 10.7MHz with a vol-
tage gain of approximately 21dB by utilising either high- or low-side injection of
the local oscillator signal. In case the mixer is interfaced only single-ended, the
unused mixer input has to be tied to ground via a capacitor. The mixer is fol-
lowed by a low pass filter with a corner frequency of 20MHz in order to suppress
RF signals to appear at the IF output (IFO pin). The IF output is internally con-
sisting of an emitter follower that has a source impedance of approximately
330Ω to facilitate interfacing the pin directly to a standard 10.7MHz ceramic filter
without additional matching circuitry.
3.4.3 PLL Synthesizer
The Phase Locked Loop synthesizer consists of a VCO, an asynchronous
divider chain, a phase detector with charge pump and a loop filter and is fully
implemented on-chip. The VCO is including spiral inductors and varactor
diodes. The FSEL pin (Pin11) has to be left open. The tuning range of the VCO
was designed to guarantee over production spread and the specified tempera-
ture range a receive frequency range between 310 and 350MHz depending on
whether high- or low-side injection of the local oscillator is used. The oscillator
signal is fed both to the synthesiser divider chain and to a divider that is dividing
the signal by 2 before it is applied to the downconverting mixer. Local oscillator
high side injection has to be used for receive frequencies between approxi-
mately 310 and 330 MHz, low side injection for receive frequencies between
330 and 350MHz - see also Section 4.4..
3.4.4 Crystal Oscillator
The on-chip crystal oscillator circuitry allows for utilisation of quartzes both in
the 5 and 10MHz range as the overall division ratio of the PLL can be switched
between 32 and 64 via the CSEL (Pin 16 ) pin according to the following table.
Table 3-2 CSEL Pin Operating States
CSEL
Open
Shorted to ground
Crystal Frequency
5.xx MHz
10.xx MHz
Wireless Components
3 - 10
Specification, May 2001