ATA5744 ATMEL Corporation, ATA5744 Datasheet - Page 8

• Manufacturer Part Number: ATA5744
• Description: Ata5744 Uhf Ask Receiver
• Manufacturer: ATMEL Corporation

4.5
8
Receiving Characteristics
ATA5744
Table 4-1.
Each BR_Range is defined by a minimum and a maximum edge-to-edge time (tee_sig). These
limits are defined in the electrical characteristics. They should not be exceeded to maintain full
sensitivity of the receiver.
The RF receiver ATA5744 can be operated with and without a SAW front-end filter. In a typical
automotive application, a SAW filter is used to achieve better selectivity. The selectivity with and
without a SAW front-end filter is illustrated in
quency is reduced by 40 dB. The plots are printed relatively to the maximum sensitivity. If a
SAW filter is used, an insertion loss of about 4 dB must be considered.
When designing the system in terms of receiving bandwidth, the LO deviation must be consid-
ered as it also determines the IF center frequency. The total LO deviation is calculated to be the
sum of the deviation of the crystal and the XTO deviation of the ATA5744. Low-cost crystals are
specified to be within ±100 ppm. The XTO deviation of the ATA5744 is an additional deviation
due to the XTO circuit. This deviation is specified to be ±30 ppm. If a crystal of ±100 ppm is
used, the total deviation is ±130 ppm in that case. Note that the receiving bandwidth and the
IF-filter bandwidth are equivalent.
Figure 4-2.
BR_1
Definition of BR_Range by the Pins BR_0 and BR_1
Receiving Frequency Response
0
0
1
1
-100.0
-20.0
-40.0
-60.0
-80.0
0.0
-6.0
-5.0 -4.0
-3.0
-2.0
BR_0
-1.0
0
1
0
1
Figure 4-1 on page
df (MHz)
0.0
1.0
without SAW
2.0
with SAW
3.0
4.0
7. Note that the mirror fre-
5.0
6.0
BR_Range
0
1
2
2
4893A–RKE–11/05