TDA5212_06 INFINEON [Infineon Technologies AG], TDA5212_06 Datasheet - Page 29

• Manufacturer Part Number: TDA5212_06
• Description: ASK/FSK 915MHz Single Conversion Receiver
• Manufacturer: INFINEON [Infineon Technologies AG]

Wireless Components
0.18 mV/kHz
1.5 V......2.5 V
typ. 2 V
FSK PLL Demodulator
4.6.1
4.6 ASK/FSK Switch Functional Description
RSSI (ASK signal)
The TDA5211 is containing an ASK/FSK switch which can be controlled via Pin
15 (MSEL). This switch is actually consisting of 2 operational amplifiers that are
having a gain of 1 in case of the ASK amplifier and a gain of 11 in case of the
FSK amplifier in order to achieve an appropriate demodulation gain character-
istic. In order to compensate for the DC-offset generated especially in case of
the FSK PLL demodulator there is a feedback connection between the thresh-
old voltage of the bit slicer comparator (Pin 20) to the negative input of the FSK
switch amplifier. This is shown in the figure below:
Figure 4-7
FSK Mode
The FSK datapath has a bandpass characterisitc due to the feedback shown
above (highpass) and the data filter (lowpass). The lower cutoff frequency f2 is
determined by the external RC-combination. The upper cutoff frequency f3 is
determined by the data filter bandwidth.
The demodulation gain of the FSK PLL demodulator is 200µV/kHz. This gain is
increased by the gain v of the FSK switch, which is 11. Therefore the resulting
dynamic gain of this circuit is 2.2mV/kHz round about within the bandpass. The
ASK mode : v=1
FSK mode : v=11
R
+
+
-
-
4
=30k
ASK
FSK
ASK/FSK mode datapath
15
R
ASK/FSK Switch
3
=300k
MSEL
R
1
FFB
=100k
4 - 8
22
R
2
=100k
C
Data Filter
2
21
OPP
v = 1
C
1
SLP
19
R
Specification, December 2006
20
-
+
SLN
C
Comp
Applications
DATA Out
TDA 5212
ask_fsk_datapath.WMF
25