TDA5220XT Infineon Technologies, TDA5220XT Datasheet - Page 17

• Manufacturer Part Number: TDA5220XT
• Manufacturer: Infineon Technologies

Specifications of TDA5220XT

• Operating Temperature (min): -40C
• Operating Temperature (max): 125C
• 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

signal level as can be seen in Figure 4. 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 in its ‘High‘-state as
described in the next chapter.
2.4.6
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 200µV/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 signal with low frequencies applied to the
demodulator demodulated to logic zero and high frequencies demodulated to logic ones.
However this is only valid in case the local oscillator is low-side injected to the mixer
which is applicable to receive frequencies above 840 or 420MHz. In case of receive
frequencies below 840 or 420MHz high frequencies are demodulated as logical zeroes
due to a sign inversion in the downconversion mixing process as the L0 is high-side
injected to the mixer. See also Section 3.4.
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 3.6.
Table 3
MSEL
Open
Shorted to ground
The demodulator circuit is switched off in case of reception of ASK signals.
2.4.7
The data filter comprises an OP-Amp with a bandwidth of 100kHz used as a voltage
follower and two 100k on-chip resistors. Along with two external capacitors a 2nd order
Preliminary Specification
FSK Demodulator
Data Filter
MSEL Pin Operating States
17
Modulation Format
ASK
FSK
Functional Description
V 1.1, 2004-10-20
TDA 5220