TDA5211XT Infineon Technologies, TDA5211XT Datasheet - Page 19

• Manufacturer Part Number: TDA5211XT
• Manufacturer: Infineon Technologies

Specifications of TDA5211XT

• Operating Temperature (min): -40C
• Operating Temperature Classification: Automotive
• Product Depth (mm): 4.4mm
• Product Length (mm): 9.7mm
• Operating Supply Voltage (min): 4.5V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / Rohs Status: Compliant

Wireless Components
3.4.5
3.4.6
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.
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
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.
FSK Demodulator
To demodulate frequency shift keyed (FSK) signals a PLL circuit is used that is
contained fully on chip. The Limiter output differential signal is fed to the linear
phase detector as is the output of the 10.7 MHz center frequency VCO. The
demodulator gain is typically 140µV/kHz. The passive loop filter output that is
comprised fully on chip is fed to both the VCO and the modulation format switch
described in more detail below. This signal is representing the demodulated sig-
nal with low frequencies applied to the demodulator demodulated to logic ones
and high frequencies demodulated to logic zeroes. However this is only valid in
case the local oscillator is low-side injected to the mixer which is applicable to
receive frequencies above 330MHz (e.g. 345MHz). In case of receive frequen-
cies below 330MHz (e.g.315MHz) high frequencies are demodulated as logical
ones due to a sign inversion in the downconversion mixing process. See also
Section 4.4.
The modulation format switch is actually a switchable amplifier with an AC gain
of 11 that is controlled by the MSEL pin (Pin 15) as shown in the following table.
This gain was chosen to facilitate detection in the subsequent circuits. The DC
gain is 1 in order not to saturate the subsequent Data Filter wih the DC offset
produced by the demodulator in case of large frequency offsets of the IF signal.
The resulting frequency characteristic and details on the principle of operation
of the switch are described in Section 4.6.
Table 3-3 MSEL Pin Operating States
MSEL
Open
Shorted to ground
3 - 11
Modulation Format
to allow for easy interfacing
Functional Description
ASK
FSK
Specification, May 2001
TDA 5211