ATA5283 ATMEL Corporation, ATA5283 Datasheet - Page 4

• Manufacturer Part Number: ATA5283
• Description: Interface ic For 125 KHZ Wake-up Function
• Manufacturer: ATMEL Corporation

Automatic Gain Control
4
ATA5283
For a correct demodulation the signal conditioner needs appropriate internal signal
amplitude. To control the input signal the ATA5283 has a build in digital AGC. The gain
control circuit regulates the internal signal amplitude to the reference value (Ref2, Fig-
ure 4). It decreases the gain by one step if the internal signal exceeds the reference
level for two periods and it increases the gain by one step if eight periods do not achieve
the reference level. In the standby listen mode the gain is reset to the maximum value. If
a valid preamble signal (192 valid carrier clocks) is detected the automatic gain control
is activated.
Note:
Figure 4. Automatic Gain Control
Internal comparator
singal
Transmitted
signal
Coil
input
Gain controlled
signal
N_DATA
With the variation of the gain the coil input impedance changes from high impedance to
minimal 143 kW because of the internal regulator circuit (see Figure 10).
Gain control
reference
Gap detection
reference
Ref.2
Ref.1
4598A–AUTO–04/03