ATA5823 ATMEL Corporation, ATA5823 Datasheet - Page 6

• Manufacturer Part Number: ATA5823
• Description: Uhf Ask/fsk Transceiver Ata5823 Ata5824
• Manufacturer: ATMEL Corporation

3. Typical Key Fob Application for Bi-directional RKE
Figure 3-1.
6
ATA5823/ATA5824
Typical Key Fob Application for Bi-directional RKE with 5 dBm TX Power, 433.92 MHz
Loop antenna
AVCC
C
Figure 3-1
10 capacitors, 1 resistor, 2 inductors and a crystal. C
capacitors. C
internal quasi-peak detector and for the high-pass frequency of the data filter. C
matching capacitors in the range of 1 pF to 33 pF. L
56 nH. L
grated. R
quality factor is somewhat reduced by this application due to the quality factor of L
RX/TX switch. On the other hand, this lower quality factor is necessary to have a robust design
with a bandwidth that is wide enough for production tolerances. Due to the single-ended and
ground-referenced design, the loop antenna can be a free-form wire around the application as it
is usually employed in RKE unidirectional systems. The ATA5823/ATA5824 provides sufficient
isolation and robust pulling behavior of internal circuits from the supply voltage as well as an
integrated VCO inductor to allow this. Since the efficiency of a loop antenna is proportional to the
square of the surrounded area, it is beneficial to have a large loop around the application board
with a lower quality factor to relax the tolerance specification of the RF matching components
and to get a high antenna efficiency in spite of their lower quality factor.
10
L
2
L
1
2
1
C
is a feed inductor of about 120 nH. A load capacitor of 9 pF for the crystal is inte-
C
shows a typical 433.92 MHz RKE key fob application. The external components are
is typically 22 k and sets the output power to about 5.5 dBm. The loop antenna’s
5
C
C
11
8
9
5
R
is a 10 nF supply blocking capacitor. C
1
C
NC
NC
NC
RF_IN
NC
433_N868
NC
R_PWR
PWR_H
RF_OUT
NC
NC
7
C
1
ATA5823/ATA5824
+
Litihum-cell
C
2
SDO_TMDO
SDI_TMDI
TEST3
CDEM
VSINT
POUT
RSSI
SCK
CLK
IRQ
1
NC
CS
1
is a matching inductor of about 5.6 nH to
6
to C
XTAL2
C
is a 15 nF fixed capacitor used for the
6
3
are 68 nF voltage supply blocking
13.25311 MHz
VCC
C
3
Microcontroller
VSS
7
4829D–RKE–06/06
to C
2
11
and the
are RF