TDA5225 Datasheet, PDF (34/176 Pages) Infineon Technologies AG – Enhanced Sensitivity Multi-Channel Quad-Configuration Receiver

TDA5225
Functional Description
2.4.7 RSSI Peak Detector
The IC possesses digital RSSI peak level detectors. The RSSI level is averaged over 4
samples before it is fed to the peak detectors. This prevents the evaluated peak values
to be dominated by single noise peaks.
fsys
ADC Sampling
Clock Generation
fAD C
A
from
D
RSSI
Generator
RSSI Slope
RSSI Offset
Divide
by 4
fA D C/4
Integrate
D um p
RSSI
I&D Averaging Filter
Compare
Peak Detector
to
ASK path
U pdate
Peak
Value
Load
RSSIPRX
R X_ R U N
from
FSM
&
Read Access to
Register RSSIPRX
from
SPI Controller
Figure 13 Peak Detector Unit
RSSIRX
Peak Detector is used to measure RSSI independent of a data transfer and to digitally
trim RSSI. It is read via SFR RSSIPRX.
Observation of the RSSI signal is active whenever the RX_RUN signal is high. The
RSSIPRX register is refreshed and the Peak Detector is reset after every read access to
RSSIPRX.
It may be required to read RSSIPRX twice to obtain the required result. This is because,
for example, during a trim procedure in which the input signal power is reduced, after
reading RSSIPRX, the peak detector will still hold the higher RSSI level. After reading
RSSIPRX the lower RSSI level is loaded into the Peak Detector and can be read by
reading RSSIPRX again.
Register RSSIPRX should not be read-out faster than 41µs in case AGC is ON (as
register value would not represent the actual, but a lower value).
When the RX_RUN signal is inactive, a read access has no influence to the peak
detector value. The register RSSIPRX is reset to 0 at power up reset.
Peak Detector Wake-Up RSSIPWU (see Figure 10) is used to measure the input signal
power during Wake-Up search. The internal signal RSSIPWU gets initialized to 0 at start
of the first observation time window at the beginning of each configuration/channel. The
peak value of this signal is tracked during Wake-Up search.
Data Sheet
34
V1.0, 2010-02-19