ATR4252 Datasheet, PDF (6/10 Pages) ATMEL Corporation – All-in-One IC Solution for Active Antennas

3.4 FM AGC
The IC is equipped with an AGC capability to prevent overdriving of the amplifier in case the
amplifier is operated at strong antenna signals, e.g., near transmitters. It is possible to realize an
additional antenna amplifier path with integrated AGC and external RF transistor. The bandwidth
of the integrated AGC circuit is 900 MHz.
FM amplifier output FMC is connected to a capacitive voltage divider and the divided signal is
applied to the AGC level detector at pin FMDET. This level detector input is optimized for low
distortion. The rectified signal is compared against an internal reference. The threshold of the
AGC can be adjusted by tuning the divider ratio of the external voltage divider. If the threshold is
reached, pin FMPD opens an internal transistor, which controls the pin-diode current. By these
means, the amplifier input signal is limited and therefore the FM amplifier is prevented from sig-
nal overdrive.
The necessary driver for the external pin diode is already incorporated in the ATR4252 IC, which
reduces the BOM cost and the application size.
3.5 Supply Voltage Regulator
The driving voltage for an external power transistor is provided by an integrated regulator circuit.
An overvoltage protection circuit recognizes overvoltage condition and switches off the amplifier
and AGC circuits in order to reduce current consumption and avoid thermal overload.
3.6 Antenna Sensor
In addition, an antenna sensor has been integrated in order to recognize if the antenna is prop-
erly connected to the amplifier module. If no antenna is detected, the amplifier and AGC circuits
are switched off in order to signal this error via reduction of supply current consumption to the
unit that provides and monitors the supply current for the antenna amplifier (e.g., the car radio).
4. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Reference point is ground.
Parameters
Pin
Symbol
Min.
Max.
Unit
Supply voltage
Collector of FM amplifier
11
V_S
–0.3
+12
V
14
FMC
3
16
V
AM LNA input terminal
23
AM LNA IN
0
2
V
AM LNA output terminal
26 AM LNA OUT
7
12
V
Power dissipation
Junction temperature
Ambient temperature
Storage temperature
ESD HBM
P_tot
1200
mW
T_j
150
°C
T_amb
–40
+105
°C
T_stg
–50
+150
°C
all
V_HBM
–2
+2
kV
6 ATR4252 [Preliminary]
9154AS–AUDR–09/09