TDA5230 Datasheet, PDF (72/186 Pages) Infineon Technologies AG – Universal Low Power ASK/FSK Single Conversion Multi-Channel Image-Reject Receiver

TDA523x
Functional Description
2,50 V
2,00 V
1,50 V
1,00 V
Typical RSSI+ over Input Signal Power
mmin _aimxiummu ^{mof fgseaitn,}
mamxiimnimumumofgf ^saeint,
trimmed
mminiinmimuummofgfsaeint,
0,50 V
-125
-115
-105
-95
-85
-75
-65
-55
-45
-35
-25
Input Signal Pow er [dBm]
Figure 33 Typical RSSI+ over Input Signal Power
The true RSSI signal is calculated by the following rule:
RSSI
=


R---R--S---E--S--F--I--++--------––_{---------RR-----ES----FS-----I----}
The result of this calculation is about -1 for no input signal (=noise), and about +1 for
large input signals (e.g. -10 dBm).
The RSSI Signals are also sampled by an AD converter, with four differential input
signals for the RSSI and the RSSI voltage reference. The true RSSI is automatically
calculated, using the following formula and the result stretched to values from 0 to 255.
RSSI
=




R---R--S---E--S--F--I--++--------––_{---------RR-----ES----FS-----I----}
+
1_
×
1--
2
×
255
The digital output of the ADC is used for processing ASK modulated data, and for two
peak detectors, which are accessible via SFRs and are described in Chapter 2.4.8.3
RSSI Peak Detector. The range of the ADC is smaller than the range of real RSSI. It is
important that the true RSSI level at noise is >-0.92, which means it is clearly inside the
ADC range. Otherwise, small input signals are not recognized and sensitivity is
decreased.
Data Sheet
68
Version 4.0, 2007-06-01