tda5235 Infineon Technologies Corporation, tda5235 Datasheet - Page 35

• Manufacturer Part Number: tda5235
• Description: Enhanced Sensitivity Double-configuration Receiver With Digital Baseband Processing
• Manufacturer: Infineon Technologies Corporation

2.4.7
The IC possesses several digital RSSI peak level detectors. The RSSI level is averaged
over 4 samples before it is fed to any of the peak detectors. This prevents the evaluated
peak values to be dominated by single noise peaks.
Figure 13
Peak Detector Payload is used to measure the input signal power of a received and
accepted data telegram. It is read via SFR RSSIPPL.
Observation of the RSSI signal starts at the detection of a TSI (FSYNC) and ends with
the detection of EOM. The internal RSSIPPL value is cleared after FSYNC. The
evaluated RSSI peak level RSSIPPL is transferred to the RSSIPPL register at EOM.
Starting the observation of the RSSI level can be delayed by a selectable number of data
bits and is controlled by the register x_PKBITPOS. A latency in the generation of FSYNC
and EOM of approx. 2..3 bits in relation to the contents of the Peak Detector must be
considered. Within the boundaries described, the register RSSIPPL always contains the
peak value of the last completely received data telegram. The register RSSIPPL is reset
to 0 at power up reset only.
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
Data Sheet
Generator
RSSI
from
Clock Generation
ADC Sampling
A
f
sys
RSSI Peak Detector
f
ADC
D
Peak Detector Unit
RSSI Offset
RSSI Slope
ASK path
to
Integrate
I&D Averaging Filter
Divide
RSSI
by 4
Dump
f
ADC
/4
35
Peak Detector
Peak Detector
Payload
Compare
Compare
Update
Value
Update
Peak-
Value
Peak
Load
Load
Functional Description
&
Peak Value
Detector
Register
Control
Update
Track
Peak
Register RSSIPRX
Read Access to
RX_RUN
V1.0, 2010-02-19
TDA5235
EOM
FSYNC
Bit
position
from
FSM
from
SPI Controller
RSSIPPL
RSSIPRX
RSSIRX