TDA5252G2 INFINEON [Infineon Technologies AG], TDA5252G2 Datasheet - Page 20

• Manufacturer Part Number: TDA5252G2
• Description: ASK/FSK 915MHz Wireless Transceiver
• Manufacturer: INFINEON [Infineon Technologies AG]

Receive Signal Strength Indicator (RSSI) generators are included in both limiters which produce DC
voltages that are directly proportional to the input signal level in the respective channels. The
resulting I- and Q-channel RSSI-signals are summed to the nominal RSSI signal.
2.4.8
The output differential signals of the I/Q limiters are fed to a quadrature correlator circuit that is used
to demodulate frequency shift keyed (FSK) signals. The demodulator gain is 2.4mV/kHz, the
maximum frequency deviation is ±300kHz as shown in Figure 2-4 below.
The demodulated signal is applied to the ASK/FSK mode switch which is connected to the input of
the data filter. The switch can be controlled by the ASKFSK pin (pin 4) and via the D11 bit in the
CONFIG register.
The modulation index m must be significantly larger than 2 and the deviation at least larger than
25kHz for correct demodulation of the signal.
Figure 2-4
2.4.9
The 2-pole data filter has a Sallen-Key architecture and is implemented fully on-chip. The bandwidth
can be adjusted between approximately 5kHz and 102kHz via the bits D4 to D7 of the LPF register
(see also Table 2-18).
Data Sheet
FSK Demodulator
Data Filter
1,6
1,5
1,4
1,3
1,2
1,1
0,9
0,8
0,7
0,6
0,5
1
-350 -300 -250 -200 -150 -100 -50
Typical Quadricorrelator Demodulation Characteristic
20
f /kHz
0
50
100 150 200 250 300 350
Functional Description
TDA5252 G2
Version 1.1
Qaudricorrelator.wmf
2007-02-26