ATR2732-40-EK2 Atmel, ATR2732-40-EK2 Datasheet - Page 6

• Manufacturer Part Number: ATR2732-40-EK2
• Description: KIT MEDIA/EVAL ATR2732+ATR2740
• Manufacturer: Atmel
• Type: DAB Digital Processingr

Specifications of ATR2732-40-EK2

• For Use With/related Products: ATR2740, ATR2732
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3.2
6
AGC in General
ATR2732 [Preliminary]
There are three AGCs in the ATR2732, one for the RF signals (around the LNAs) (1) and (3),
one for the very beginning of the IF path (mainly VHF mixer), and one for the IF amplifiers (5)
down to the output to baseband (7).
In these AGCs, the output signals of the relevant blocks are amplified, weakly band-pass fil-
tered, rectified, and, finally, low-pass filtered. The voltage derived in this power-measurement
process is compared to a voltage threshold which can be digitally controlled by several bits,
independently of each other. The setting is done via the control bus. Depending on the result of
this comparison, charge pumps feed a positive or negative current in order to charge or dis-
charge external capacitors. The voltage of these external capacitors is used to control the gains
of practically all blocks in the signal path.
By means of the control bus, the current of the AGC charge pump can be selected as specified
in the following table:
Table 3-1.
The input pin WAGC, set to logical 1, always sets all AGCs to time constant Infinite (meaning
there is practically no current to the AGC capacitors), regardless of the actual status of the bus
settings.
MSB
0
0
0
0
1
1
1
1
Selection of Time Constant Factor
0
0
1
1
0
0
1
1
LSB
0
1
0
1
0
1
0
1
Time Constant Factor
Infinite
32
16
8
4
2
1
0.2
4918AS–DAB–03/06