TDA7210 Datasheet, PDF (19/52 Pages) Infineon Technologies AG – Wireless Components ASK/FSK Single Conversion Receiver

TDA7210
Functional Description
sary.
The oscillator signal is fed both to the synthesiser divider chain and to the down-
converting mixer. In case of operation in the 400 to 440 MHz range, the signal
is divided by two before it is fed to the mixer. This is controlled by the selection
pin FSEL (Pin 11) as described in the following table. The overall division ratio
of the divider chain can be selected to be either 128 or 64, depending on the
frequency of the reference oscillator quartz (see below and Section 4.4). The
loop filter is also realised fully on-chip.
Table 3-2 FSEL Pin Operating States
FSEL
Open
Shorted to ground
RF Frequency
400-440 MHz
810-870 MHz
3.4.4 Crystal Oscillator
The on-chip crystal oscillator circuitry allows for utilisation of quartzes both in
the 6 and 13MHz range as the overall division ratio of the PLL can be switched
between 64 and 128 via the CSEL (Pin 16) pin according to the following table.
Table 3-3 CSEL Pin Operating States
CSEL
Open
Shorted to ground
Crystal Frequency
6.xx MHz
13.xx MHz
The calculation of the value of the necessary quartz load capacitance is shown
in Section 4.3, the quartz frequency calculation is explained in Section 4.4.
3.4.5 Limiter
The Limiter is an AC coupled multistage amplifier with a cumulative gain of
approximately 80 dB that has a bandpass-characteristic centred around
10.7 MHz. It has a typical input impedance of 330 Ω to allow for easy interfacing
to a 10.7 MHz ceramic IF filter. The limiter circuit also acts as a Receive Signal
Strength Indicator (RSSI) generator which produces a DC voltage that is
directly proportional to the input signal level as can be seen in Figure 4-2. This
signal is used to demodulate ASK-modulated receive signals in the subsequent
baseband circuitry. The RSSI output is applied to the modulation format switch,
to the Peak Detector input and to the AGC circuitry.
In order to demodulate ASK signals the MSEL pin has to be left open as
described in the next chapter.
Wireless Components
3 - 11
Data Sheet, December 2008