ATR2732N3 Datasheet, PDF (7/14 Pages) ATMEL Corporation – Integrated DAB One-chip Front End

ATR2732N3
3.3 Device Support Functions
The ATR2732N3 has incorporated some very useful additional functions for handling the device
and optimizing the performance. First of all, a very precise clocking engine is incorporated. To
optimize the performance of this front end, a tuning support for alignment of the filters is featured
by this part too, similar to Atmel’s other radio front ends.
3.4 Tuning Support Functions
The ATR2732N3 includes three operational amplifiers, and three programmable digital-analog
converters (DACs). These outputs are used for automatic filter alignment of the tunable VHF
antenna filter and the preselection filter. DACs are incorporated in the ATR2732N3 for this tun-
ing-support function.
For more details about the usage of the filter-tuning function contact your local Atmel sales office
and ask for the application note covering this feature.
3.5 DAC Usage
There are two DAC modes: pure DAC and Loop/Offset mode. In the pure DAC mode the DAC
sets a definite value. In the Loop/Offset mode the filter tuning voltage is derived from a reference
tank circuit (inductor plus varicap). An offset value can be added to this voltage. This Loop/Off-
set mode is the most useful mode and recommended for most applications. Temperature
compensation is also included in this mode.
3.6 RSSI Measurement
The ATR2732N3 offers the option of getting information about the field strength. This is not an
absolute real-field-strength value, but an indication of in which range the field strength is avail-
able. This information can be obtained from the 8 low bits of the status register.
3.7 Clocking Engine in General
The ATR2732N3 incorporates a convenient and flexible clocking engine. This includes VCOs
and PLLs for both bands, as well as a reference oscillator which can be precisely tuned using
the SPI interface. Together, this results in low external component count, but offers high flexibil-
ity and convenience.
3.8 PLL Part
The two PLL parts, the L-band PLL and the Band III PLL, perform phase lock of the LO signal to
an on-chip crystal reference oscillator. The Band III PLL incorporates a fractional part. This tech-
nique allows operation with an increased bandwidth of the PLL, which results in improved phase
noise.
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9129AS–DAB–04/08