ATA5749-EK2 Atmel, ATA5749-EK2 Datasheet - Page 8

• Manufacturer Part Number: ATA5749-EK2
• Description: BOARD EVALUATION TPMS 433MHZ
• Manufacturer: Atmel
• Type: Transmitterr

Specifications of ATA5749-EK2

• Frequency: 433MHz
• For Use With/related Products: ATA5749
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.1.1
8
Atmel ATA5749
Antenna Impedance Matching
The PCB loop antenna should not exceed a trace width of 1.5mm otherwise the Q-factor of the
loop antenna is too high. C4 and C5 should be selected so that the XTO runs on the load reso-
nance frequency of the crystal. A crystal with a load capacitance of 9pF is recommended for
proper start-up behavior and low current consumption. When determining values for C4 and C5,
a parasitic capacitance of 3pF should be included. With value of 15pF for C4 and C5, an effec-
tive load capacitance of 9pF can be achieved, e.g., 9pF = (15pF + 3pF)/2. The supply V
typically delivered from a single Li-Cell.
The maximum output power is achieved by using load impedances according to
page 9
the impedance seen from the Atmel
not the output impedance of the IC but essentially the peak voltage divided by the peak current
with some additional parasitic effects (Cpar).
not contain information pertaining to C3 in
low power steps.
Figure 4-2
ure 4-3 on page 10
Table 4-2 on page 9
power levels. For reference, Z
ANT1, ANT2 into the matching network.
Figure 4-2.
and
is the circuit that was used to obtain the typical output power measurements in
Table 4-2 on page 9
Output Power Measurement Circuit
Power Meter
and typical current consumption in
50
provide recommended values and performance info at various output
LOPT
and the output power. The load impedance Z
is defined as the impedance seen from the Atmel ATA5749
C3
®
C2
ATA5749 ANT1, ANT2 into the matching network. This is
VS
Z
L1
Figure
LOPT
Table 4-1 on page 9
4-2, which is an option for better matching at
ANT2
ANT1
C1
4
5
Figure 4-4 on page
PA
and
Table 4-2 on page 9
10.
LOPT
Table 4-1
9128G–RKE–03/11
Table 4-1 on
is defined as
Fig-
and
S
do
is