ATA8403 ATMEL Corporation, ATA8403 Datasheet - Page 5

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ATA8403

Manufacturer Part Number
ATA8403
Description
Manufacturer
ATMEL Corporation
Datasheet
4.3
4.3.1
4.3.2
4983A–IND–02/07
CLK Output
Clock Pulse Take-over
Output Matching and Power Setting
Figure 4-1.
Using C
tances on each side of the crystal of C
crystal of C
ation of ±21.5 kHz with worst case tolerances of ±16.8 kHz to ±28.0 kHz.
An output CLK signal is provided for a connected microcontroller. The delivered signal is CMOS
compatible if the load capacitance is lower than 10 pF.
The clock of the crystal oscillator can be used for clocking the microcontroller. A special feature
of Atmel
with ENABLE = H, and after 4 ms assumes the clock signal of the transmission IC, so that the
message can be sent with crystal accuracy.
The output power is set by the load impedance of the antenna. The maximum output power is
achieved with a load impedance of Z
resistive path to V
The delivered current pulse of the power amplifier is 7.7 mA. The maximum output power is
delivered to a resistive load of 475 if the 0.53 pF output capacitance of the power amplifier is
compensated by the load impedance.
An optimum load impedance of:
Z
of 5.5 dBm.
The load impedance is defined as the impedance seen from the ATA8403’s ANT1, ANT2 into
the matching network. Do not confuse this large signal load impedance with a small signal input
impedance delivered as input characteristic of RF amplifiers and measured from the application
into the IC instead of from the IC into the application for a power amplifier.
Less output power is achieved by lowering the real parallel part of 475 where the parallel imag-
inary part should be kept constant.
Output power measurement can be done with the circuit shown in
that the component values must be changed to compensate for the individual board parasitics
until the ATA8403 has the right load impedance Z
damping of the cable used to measure the output power must be calibrated out.
Load
= 475 || j/(2
4
®
= 9.2 pF ±2%, C
’s ATARx9x is that it starts with an integrated RC-oscillator to switch on the ATA8403
0
= 3.2 pF ±10% and a crystal with C
Tolerances of Frequency Modulation
XTAL
S
to deliver the DC current.
V
p
S
f
5
= 6.8 pF ±5%, a switch port with C
0.53 pF) = (166 + j226) thus results in the maximum output power
C
Stray1
Load,opt
C
Stray1
M
= (166 + j226) at 868.3 MHz. There must be a low
L
= C
C
M
0
Stray2
M
= 13 fF ±10%, typically results in an FSK devi-
Load,opt
R
S
= 1 pF ±10%, a parallel capacitance of the
= (166 + j226) at 868.3 MHz. Also the
C
Switch
Stray2
C
5
Figure 4-2 on page
= 3 pF ±10%, stray capaci-
C
Switch
C
4
ATA8403
6. Note
5

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