ATAB8402 Atmel, ATAB8402 Datasheet - Page 8

• Manufacturer Part Number: ATAB8402
• Description: BOARD DEMO 433MHZ RF TRANSMITTER
• Manufacturer: Atmel
• Type: Transmitterr

Specifications of ATAB8402

• Frequency: 433MHz
• Wireless Frequency: 315 MHz
• Modulation: ASK, FSK
• For Use With/related Products: ATA8402
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

2.3.1
2.3.2
2.4
8
Crystal Oscillator
ATA8401/ATA8402/ATA8403
ASK (OOK) Transmission
FSK Transmission
The load capacitor of the crystal (C1 in
quency. For ASK modulation, the PA_ENABLE will be switched alternating between high and
low voltage due to the data to be transmitted. This results in the switching on and off of the
power amplifier, which is known as OOK (On Off Keying).
The crystal pulling method is used for the FSK modulation
capacitor C2 will be used to modulate the crystal resonance frequency due to the data to be
transmitted. For this purpose the capacitor C2 will be connected to the capacitor C1 related to
the data. In practical terms this is a connection between capacitor C2 and the open drain port of
a microprocessor. In the event of modulation, the microprocessor switches the capacitor C2
alternately between high impedance condition and ground. This method pulls the crystal's series
resonance frequency between two values, which results in the RF operating frequency.
The crystal oscillator uses the crystal’s series resonance frequency to generate the reference
frequency. The series connection of the crystal and the load capacitor results in an impedance
Z
oscillate on the loaded resonance frequency f
means the imaginer part of the impedance Im{Z
The impedance Z
(pin 5) in steady state oscillation. For the oscillation start-up, the following conditions must be ful-
filled (see
Im{Z
Re{Z
Figure 2-8.
To achieve the condition described by equation 13 at the specified loaded crystal frequency, the
capacitance CL can be determined as:
With lm{Z
C
XTAL
L
=
XTO
XTO
------------------------------------ -
2 f
seen from the pin XTAL (pin 5). According to the crystal’s specification, the crystal will
+ Z
+ Z
L
XTAL
lm Z
Figure
1
XTAL
XTAL
} = –lm{Z
XTAL
Condition for Oscillation Start Up
} = 0
} < 0
2-8).
XTO
is the large signal input impedance of the XTO seen into the pin XTAL
XTO
}
Equation 13
Equation 14
Equation 15
XTAL
VS
Figure
Z
XTO
2-7a) is used to adjust the desired RF transmit fre-
XTAL
Z
L
XTAL
, in which the impedance Z
} is 0 .
XTAL
C
L
(seeFigure
2-7b). An additional
XTAL
9115A–INDCO–01/08
is real. This