ATA5824-PLQW 80 Atmel, ATA5824-PLQW 80 Datasheet - Page 13

• Manufacturer Part Number: ATA5824-PLQW 80
• Manufacturer: Atmel

Specifications of ATA5824-PLQW 80

• Operating Temperature (min): -40C
• Operating Temperature (max): 105C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 7mm
• Product Height (mm): 0.9mm
• Product Length (mm): 7mm
• Operating Supply Voltage (typ): 5V
• Lead Free Status / Rohs Status: Compliant

7.4
7.5
4829D–RKE–06/06
Frequency Accuracy of the Crystals in Bi-directional RKE/PEG
Frequency Accuracy of the Crystals in a Combined RKE/PEG and TPM System
As can be seen in
sitivity. The temperature has an influence of about +1.5/
±85 kHz also influences by about ±1 dB. All these influences, combined with the sensitivity of a
typical IC (
supply voltage and frequency offset. The integrated IF filter has an additional production toler-
ance of ±10 kHz, hence, a frequency offset between the receiver and the transmitter of ±75 kHz
can be accepted for XTAL and XTO tolerances.
Note:
This small sensitivity change over supply voltage, frequency offset and temperature is very
unusual in such a receiver. It is achieved by an internal, very fast and automatic frequency cor-
rection in the FSK demodulator after the IF filter, which leads to a higher system margin. This
frequency correction tracks the input frequency very quickly, if however, the input frequency
makes a larger step (e.g., if the system changes between different communication partners), the
receiver has to be restarted. This can be done by switching back to IDLE mode and then again
to RX mode. For that purpose, an automatic mode is also available. This automatic mode
switches to IDLE mode and back into RX mode every time a bit error occurs (see section
Control Logic” on page
The XTO is an amplitude regulated Pierce type oscillator with integrated load capacitors. The ini-
tial tolerances (due to the frequency tolerance of the XTAL, the integrated capacitors on XTAL1,
XTAL2 and the XTO’s initial transconductance gm) can be compensated to a value within
±0.5 ppm by measuring the CLK output frequency and tuning of f
registers 2 and 3 (see
a remaining influence of less than ±2 ppm overtemperature and supply voltage due to the band-
gap controlled gm of the XTO. Thus only 2.5 ppm add to the frequency stability of the used
crystals overtemperature and aging.
The needed frequency stability of the used crystals overtemperature and aging is hence
± 7 5 k H z / 4 3 3 . 9 2 M H z
±75 kHz/868.3 MHz
receiver and transmitter each need to be better than ±83.9 ppm for 433.92 MHz and ±40.7 ppm
for 868.3 MHz.
In a tire pressure measurement system working at 433.92 MHz and using a TPM transmitter
ATA5757 and a transceiver ATA5824 as a receiver, the higher frequency tolerances and the tol-
erance of the frequency deviation of this transmitter has to be considered.
In the TPM transmitter the crystal has an frequency error overtemperature
aging and tolerance of ±80 ppm (±34.7 kHz at 433.92 MHz). The tolerances of the XTO, the
capacitors used for FSK-Modulation and the stray capacitors, causing an additional frequency
error of ±30 ppm (±13 kHz at 433.92 MHz). The frequency deviation of such a transmitter varies
between ±16 kHz and ±24 kHz, since a higher frequency deviation is equivalent to an frequency
error, this has to be considered as an additional ±24 kHz
erance. All tolerances added, these transmitters have a worst case frequency offset of
±52.2 kHz.
For the demodulator used in the ATA5823/ATA5824, the tolerable frequency offset does not
change with the data frequency, hence, the value of ±75 kHz is valid for 1 Kbit/s to 20 Kbit/s.
–
105.5dBm), are then within a range of
Figure 7-2 on page 12
–
Table 12-7 on page 38
2
35).
–
±2.5 ppm = ±81.4 ppm for 868.3 MHz. Thus, the used crystals in
2
± 2 . 5 p p m = ± 1 6 7 . 8 4 p p m
the supply voltage has almost no influence on the sen-
and
–
Table 12-10 on page
102.5 dBm and
–
±19.5 kHz = ±4.5kHz frequency tol-
ATA5823/ATA5824
–
0.7 dB and a frequency offset of
RF
f o r
–
by programming the control
107 dBm overtemperature,
4 3 3 . 9 2 M H z
39). The XTO then has
–
40°C to +125°C,
“Digital
a n d
13