ATR4253-PVQW Atmel, ATR4253-PVQW Datasheet - Page 3

• Manufacturer Part Number: ATR4253-PVQW
• Description: IC ALL-IN-ONE FM ANT MX 16VQFN
• Manufacturer: Atmel

Specifications of ATR4253-PVQW

• Function: Antenna Amplifier
• Frequency: 76MHz ~ 108MHz
• Rf Type: FM
• Package / Case: 16-VFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3. Functional Description
3.1
3.2
9194CS–AUDR–10/10
RF Amplifier Stage
AGC
The Atmel
and functions. It compensates cable losses between the antenna and the car radio, which is
usually placed far away from the antenna. The device can be used in the frequency range of
50 up to 900MHz (i.e. FM, DAB (+), DMB, DVB-T, ISDB-T, etc.) and has the flexibility to
address different antenna types (e.g., glass, windscreen, roof antennas).
A separate automatic gain control (AGC) function is integrated in order to avoid overdriving the
RF amplifier at large signal conditions.
The integrated PIN diode drivers help to reduce the external component cost and to minimize
the board space.
The external component cost can be further reduced as the voltage regulation stage is also
integrated. This stage provides overvoltage protection and current limitation. An external tran-
sistor is used as power driver for this stage.
The RF amplifier is realized with a high-performance NPN transistor. This allows the use of an
amplifier configuration which is optimized for the individual application requirements. For
low-cost applications, the common emitter configuration enables good performance at reason-
able BOM cost. For high-end applications, a common base configuration with transformer
feedback provides high IP3 and low noise figures at reasonable current consumption. In both
configurations, gain, input and output impedance can be adjusted by modifying the external
components.
The bias voltage (BIAS) for the base of the NPN transistor is derived from an integrated volt-
age reference and has a PTAT (proportional to absolute temperature) behavior. The bias
current of the RF amplifier is defined by an external resistor and is kept constant over
temperature.
The IC is equipped with an AGC functionality to prevent overdriving 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 900MHz.
The amplifier output (RFC) is connected to a capacitive voltage divider and the divided signal
is applied to the AGC level detector at pin DET. This level detector input is optimized for low
distortion. The rectified signal is compared against an internal reference. The divider ratio of
the external voltage divider defines the AGC’s threshold. If the threshold is reached, pin PD1
drives a positive current through one or two external pin diodes in shunt configuration. In case
the limiting range of the shunt configuration is not sufficient, an additional pin diode in serial
configuration can be added and controlled via pin PD2. The current from PD2 through the
serial pin diode is opposite to the current of PD1. This helps to limit the amplifier input signal
and thus to prevent the FM amplifier from signal overdrive.
The drivers required for the external pin diode(s) are built-in into the ATR4253 IC, which
reduces the BOM cost and the application size.
®
ATR4253 is a highly integrated antenna amplifier with a broad range of features
Atmel ATR4253
3