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PDF ATA3745 Data sheet ( Hoja de datos )
| Número de pieza | ATA3745 | |
| Descripción | UHF ASK/FSK Receiver | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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Features
• Supply Voltage 4.5V to 5.5V
• Operating Temperature Range –40°C to +85°C
• Minimal External Circuitry Requirements, No RF Components on the PC Board Except
Matching to the Receiver Antenna
• High Sensitivity, Especially at Low Data Rates
• Sensitivity Reduction Possible Even While Receiving
• Fully Integrated VCO
• Low Power Consumption Due to Configurable Self-polling with a Programmable Time
Frame Check
• Single-ended RF Input for Easy Matching to λ / 4 Antenna or Printed Antenna on PCB
• Low-cost Solution Due to High Integration Level
• ESD Protection According to MIL-STD 883 (4 KV HBM) Except Pin POUT (2 KV HBM)
• High Image Frequency Suppression Due to 1 MHz IF in Conjunction With a SAW
Front-end Filter. Up to 40 dB is Thereby Achievable With Newer SAWs
• Programmable Output Port for Sensitivity Selection or for Controlling External
Periphery
• Communication to the Microcontroller Possible via a Single, Bi-directional Data Line
• Power Management (Polling) is also Possible by Means of a Separate Pin via the
Microcontroller
UHF ASK/FSK
Receiver
ATA3745
1. Descriptionwww.DataSheet4U.com
The ATA3745 is a multi-chip PLL receiver device supplied in an SO20 package. It has
been specially developed for the demands of RF low-cost data transmission systems
with low data rates from 1 kBaud to 10 kBaud in Manchester or Bi-phase code. The
receiver is well-suited to operate with Atmel’s PLL RF transmitter ATA2745. It can be
used in the frequency receiving range of f0 = 310 MHz to 440 MHz for ASK data trans-
mission. All the statements made below refer to 433.92 MHz and 315 MHz
applications.
The main applications of the ATA3745 are in the areas of outside temperature meter-
ing, socket control, garage door openers, consumption metering, light/fan or
air-conditioning control, jalousies, wireless keyboards, and various other consumer
market applications.
Rev. 4901A–RKE–11/05
1 page  
ATA3745
To determine fLO, the construction of the IF filter must be considered at this point. The nominal IF
frequency is fIF = 1 MHz. To achieve a good accuracy of the filter’s corner frequencies, the filter
is tuned by the crystal frequency fXTO. This means that there is a fixed relation between fIF and
fLO that depends on the logic level at pin MODE. This is described by the following formulas:
MODE
=
0 (USA) fIF
=
-f--L---O---
314
MODE
=
1 (Europe) fIF
=
------f--L--O-------
432.92
The relation is designed to achieve the nominal IF frequency of fIF = 1 MHz for most applica-
tions. For applications where fRF = 315 MHz, the MODE must be set to “0”. In the case of
fRF = 433.92 MHz, the MODE must be set to “1”. For other RF frequencies, fIF is not equal to
1 MHz. fIF is then dependent on the logical level at pin MODE and on fRF. Table 3-1 summarizes
the different conditions.
The RF input either from an antenna or from a generator must be transformed to the RF input
pin LNA_IN. The input impedance of that pin is provided in the electrical parameters. The para-
sitic board inductances and capacitances also influence the input matching. The RF receiver
ATA3745 exhibits its highest sensitivity at the best signal-to-noise ratio (SNR) in the LNA.
Hence, noise matching is the best choice for designing the transformation network.
A good practice when designing the network is to start with power matching. From that starting
point, the values of the components can be varied to some extent to achieve the best sensitivity.
If a SAW is implemented into the input network, a mirror frequency suppression of ∆PRef = 40 dB
can be achieved. There are SAWs available that exhibit a notch at ∆f = 2 MHz. These SAWs
work best for an intermediate frequency of IF = 1 MHz. The selectivity of the receiver is also
improved by using a SAW. In typical automotive applications, a SAW is used.
Figure 3-2 on page 6 shows a typical input matching network for fRF = 315 MHz and
fRF = 433.92 MHz using a SAW. Figure 3-3 on page 6 illustrates an input matching to 50Ω with-
out a SAW. The input matching networks shown in Figure 3-3 on page 6 are the reference
networks for the parameters given in the section “Electrical Characteristics” on page 23.
Table 3-1. Calculation of LO and IF Frequency
Conditions
Local Oscillator Frequency
fRF = 315 MHz, MODE = 0
fRF = 433.92 MHz, MODE = 1
fLO = 314 MHz
fLO = 432.92 MHz
300 MHz < fRF < 365 MHz, MODE = 0
fLO
=
------f--R----F-------
1 + ----1-----
314
Intermediate Frequency
fIF = 1 MHz
fIF = 1 MHz
fIF
=
-f--L---O---
314
365 MHz < fRF < 450 MHz, MODE = 1
fLO
=
-----------f--R---F-----------
1 + --------1---------
432.92
fIF
=
------f--L--O-------
432.92
4901A–RKE–11/05
5
5 Page 
ATA3745
5.2.1
Sleep Mode
The length of period TSleep is defined by the 5-bit word Sleep of the OPMODE register, the exten-
sion factor XSleep described inTable 5-8 on page 20, and the basic clock cycle TClk. It is
calculated to be:
TSleep = Sleep × XSleep × 1024 × TClk
In US and European applications, the maximum value of TSleep is about 60 ms if XSleep is set to 1.
The time resolution is about 2 ms in that case. The sleep time can be extended to almost half a
second by setting XSleep to 8. XSleep can be set to 8 by bit XSleepStd or by bit XSleepTemp, resulting in
a different mode of action as described below:
XSleepStd = 1 implies the standard extension factor. The sleep time is always extended.
XSleepTemp = 1 implies the temporary extension factor. The extended sleep time is used as long
as every bit check is OK. If the bit check fails once, this bit is set back to 0 automatically, result-
ing in a regular sleep time. This functionality can be used to save current in presence of a
modulated disturber similar to an expected transmitter signal. The connected microcontroller is
rarely activated in that condition. If the disturber disappears, the receiver switches back to regu-
lar polling and is again sensitive to appropriate transmitter signals.
Table 5-6 on page 19 shows how the highest register value of Sleep sets the receiver to a per-
manent sleep condition. The receiver remains in that condition until another value for Sleep is
programmed into the OPMODE register. This function is desirable where several devices share
a single data line.
4901A–RKE–11/05
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet ATA3745.PDF ] | |
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