ATA8202-PXQW Atmel, ATA8202-PXQW Datasheet - Page 15

• Manufacturer Part Number: ATA8202-PXQW
• Description: RF Wireless Misc Switchable Rx-IC f/Industrial(433MHz)
• Manufacturer: Atmel

Specifications of ATA8202-PXQW

• Package / Case: QFN-24
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2.8
3. XTO
4971C–INDCO–04/09
Frequency Synthesizer
The LO generates the carrier frequency for the mixer via a PLL synthesizer. The XTO (crystal
oscillator) generates the reference frequency f
erates the drive voltage frequency f
32 (ATA8202). The divided frequency is compared to f
current output of the phase frequency detector is connected to the fully integrated loop filter, and
thereby generates the control voltage for the VCO. By means of that configuration, the VCO is
controlled in a way, such that f
calculated using the following formula: f
phase noise of –130 dBC/Hz at 3 MHz and spurs of –75 dBC.
Care must be taken with the harmonics of the CLK output signal, as well as with the harmonics
produced by a microprocessor clocked using the signal, as these harmonics can disturb the
reception of signals.
The XTO is an amplitude-regulated Pierce oscillator type with external load capacitances
(2
side, the load capacitance amounts to 2
The XTO oscillation frequency f
When designing the system in terms of receiving and transmitting frequency offset, the accuracy
of the crystal and XTO have to be considered.
The XTO’s additional pulling (including the R
perature, aging, and tolerances is then the main source of frequency error in the local oscillator.
The XTO frequency depends on XTAL properties and the load capacitances C
and XTAL2. The pulling (p) of f
mula:
C
capacitance of the XTAL, are found in the datasheet. C
the crystal in the circuit, and consists of C
Figure 3-1.
p
m
=
, the crystal’s motional capacitance; C
C
------- -
16 pF). Due to additional internal and board parasitics (C
2
m
---------------------------------------------------------------
C
O
+
Crystal Equivalent Circuit
C
C
LN
LN
C
–
L1
C
C
L
O
XTAL
+
C
L
LO
XTO
XTO
/ 24 (f
10
LO
from the nominal f
-6
is the reference frequency for the integer-N synthesizer.
C
ppm
for the mixer. f
L2
LO
XTO
L1
/ 32) is equal to f
0
18 pF (9 pF total).
, the shunt capacitance; and C
and C
M
= f
tolerance) is only ±5 ppm. The XTAL versus tem-
XTO
LO
. The VCO (voltage-controlled oscillator) gen-
L2
/ 24 (f
C
connected in series.
Crystal Equivalent Circuit
LO
L
XTO
= C
XTAL
is divided by the factor 24 (ATA8201) or
L
L
m
XTO
L1
is the total actual load capacitance of
by the phase frequency detector. The
is calculated using the following for-
XTO
ATA8201/ATA8202
C
= f
C
L2
P
. If f
m
/ (C
) of approximately 2 pF on each
LO
C
0
L1
/ 32). The synthesizer has a
LO
R
+ C
m
is determined, f
L2
)
LN
, the nominal load
L1,2
at pin XTAL1
XTO
can be
15