TDA5225 Datasheet, PDF (37/176 Pages) Infineon Technologies AG – Enhanced Sensitivity Multi-Channel Quad-Configuration Receiver

TDA5225
Functional Description
between 8 and 16 samples per chip. The oversampling factor within this range is
depending on the data rate (see Figure 10). The MF has to be adjusted accordingly to
this oversampling. After the MF a fractional sample rate converter (SRC) is applied using
linear interpolation. Depending on the data rate decimation is adjusted within the range
1...2. Finally, at the output of the fractional SRC the sampling rate is adjusted to 8
samples per chip for further processing.
2.4.8.2 Wake-Up Generator
A wake-up generation unit is used only in the Self Polling Mode for the detection of
exceeding a predefined level for RSSI, which then leads to a wake-up and to a change
to Run Mode Self Polling.
A configurable observation time for Wake-up on RSSI can be set in the x_WULOT
register. The Wake-up on RSSI criterion can be handled very quickly for FSK
modulation, while in case of ASK the nature of this modulation type has to be kept in
mind.
RSSI Level
x_WURSSIBHy
x_WURSSIBLy
Compare
Exceeding Threshold
x_WURSSITHy
Figure 16 Wake-Up Generation Unit
Wake-up
Generation
FSM
WU
No WU
The threshold x_WURSSITHy is used to decide whether the actual signal is a wanted
signal or just noise. Any kind of interfering RSSI level can be blocked by using an RSSI
blocking window. This window is determined by the thresholds x_WURSSIBLy and
x_WURSSIBHy, where y represents the actual RF channel. These two thresholds can
be evaluated during normal operation of the application to handle the actual interferer
environment.
The blocking window can be disabled by setting x_WURSSIBHy to the minimum value
and x_WURSSIBLy to the maximum value.
Data Sheet
37
V1.0, 2010-02-19