6

9154AS–AUDR–09/09

ATR4252 [Preliminary]

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

11

–0.3

+12

V

Collector of FM amplifier

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

1200

mW

Junction temperature

150

°C

Ambient temperature

–40

+105

°C

Storage temperature

–50

+150

°C

ESD HBM

all

–2

+2

kV