ATA5283_07 ATMEL [ATMEL Corporation], ATA5283_07 Datasheet - Page 4

• Manufacturer Part Number: ATA5283_07
• Description: Interface IC for 125 kHz Wake-up Function
• Manufacturer: ATMEL [ATMEL Corporation]

3.3
4
Automatic Gain Control
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 regu-
lates the internal signal amplitude to the reference value (Ref2,
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 3-2.
Gain controlled
Internal comparator
Transmitted
With the variation of the gain the coil input impedance changes from high impedance to minimal
143 k because of the internal regulator circuit (see
signal
signal
input
Coil
N_DATA
signal
Automatic Gain Control
Gap detection
Gain control
reference
reference
Ref. 2
Ref. 1
Figure 3-8 on page
Figure
8).
3-2). It decreases the
50%
4598H–AUTO–03/07
100%