tda5225 Infineon Technologies Corporation, tda5225 Datasheet - Page 34

• Manufacturer Part Number: tda5225
• Description: Enhanced Sensitivity Multi-channel Quad-conf Igurat Ion Receiver With Digital Slicer
• Manufacturer: Infineon Technologies Corporation

2.4.7
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.
Figure 13
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
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
Generator
RSSI
from
Clock Generation
ADC Sampling
A
f
sys
RSSI Peak Detector
f
AD C
D
Peak Detector Unit
RSSI Offset
RSSI Slope
ASK path
to
Integrate
I&D Averaging Filter
Divide
RSSI
by 4
Dump
Figure
34
f
AD C
/4
10) is used to measure the input signal
Peak Detector
Compare
Update
Value
Peak
Load
Functional Description
&
Register RSSIPRX
Read Access to
V1.0, 2010-02-19
RX_RUN
TDA5225
from
FSM
from
SPI Controller
RSSIPRX
RSSIRX