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PDF T5743 Data sheet ( Hoja de datos )
| Número de pieza | T5743 | |
| Descripción | UHF ASK/FSK Receiver | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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Features
• Two Different IF Receiving Bandwidth Versions Are Available (BIF = 300 kHz or 600 kHz)
• 5 V to 20 V Automotive Compatible Data Interface
• IC Condition Indicator, Sleep or Active Mode
• Low Power Consumption Due to Configurable Self Polling with a Programmable
Timeframe Check
• High Sensitivity, Especially at Low Data Rates
• Data Clock Available for Manchester- and Bi-phase-coded Signals
• Minimal External Circuitry Requirements, no RF Components on the PC Board Except
Matching to the Receiver Antenna
• Sensitivity Reduction Possible Even While Receiving
• Fully Integrated VCO
• SO20 Package
• Supply Voltage 4.5 V to 5.5 V, Operating Temperature Range -40°C to +105°C
• Single-ended RF Input for Easy Adaptation to λ/4 Antenna or Printed Antenna on PCB
• Low-cost Solution Due to High Integration Level
• ESD Protection According to MIL-STD. 883 (4KV 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 State-of-the-art SAWs.
• Communication to Microcontroller Possible Via a Single, Bi-directional Data Line
• Power Management (Polling) Is Also Possible by Means of a Separate Pin Via the
Microcontroller
• Programmable Digital Noise Suppression
UHF ASK/FSK
Receiver
T5743
Preliminary
Description
The T5743 is a multi-chip PLL receiver device supplied in an SO20 package. It has
been especially developed for the demands of RF low-cwowsw.tDadtaaShteaet4Utr.caomnsmission systems
with 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 U2741B. Its main
applications are in the areas of telemetering, security technology and keyless-entry
systems. It can be used in the frequency receiving range of f0 = 300 MHz to 450 MHz
for ASK or FSK data transmission. All the statements made below refer to 433.92 MHz
and 315 MHz applications.
System Block Diagram
Figure 1. System Block Diagram
UHF ASK/FSK
Remote control transmitter
U2741B
XTO
PLL
VCO
Antenna
Power
amp.
T5743
UHF ASK/FSK
Remote control receiver
Demod.
Control
1...5
µC
Antenna
IF Amp
PLL
XTO
LNA
VCO
Rev. 4569A–RKE–12/02
1
1 page  
T5743
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
applications. For applications where fRF = 315 MHz, MODE must be set to ‘0’. In the
case of fRF = 433.92 MHz, 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 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 parame-
ters. The parasitic board inductances and capacitances also influence the input
matching. The RF receiver T5743 exhibits its highest sensitivity at the best signal-to-
noise ratio in the LNA. Hence, noise matching is the best choice for designing the trans-
formation 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
DPRef = 40 dB can be achieved. There are SAWs available that exhibit a notch at
Df = 2 MHz. These SAWs work best for an intermediate frequency of fIF = 1 MHz. The
selectivity of the receiver is also improved by using a SAW. In typical automotive appli-
cations, a SAW is used.
Figure 5 shows a typical input matching network, for fRF = 315 MHz and fRF =
433.92 MHz using a SAW. Figure 6 illustrates an according input matching to 50 W
without a SAW. The input matching networks shown in Figure 6 are the reference net-
works for the parameters given in the electrical characteristics.
Table 1. Calculation of LO and IF Frequency
Conditions
Local Oscillator Frequency
fRF = 315 MHz, MODE = 0
fRF = 433.92 MHz, MODE = 1
300 MHz < fRF < 365 MHz,
MODE = 0
fLO = 314 MHz
fLO = 432.92 MHz
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
4569A–RKE–12/02
5
5 Page 
Sleep Mode
T5743
ISpoll = I--S----o--f--f--´-----T---T-S---Sl-e--l-ee---ep--p--+--+---I--ST---o-S--n-t--a-´-r--t-u(---Tp----S+---t-a-T--r--tB-u--i-pt----c-+-h---e-T--c--Bk---i-t----c--h---e---c--k---)
During TSleep and TStartup the receiver is not sensitive to a transmitter signal. To guaran-
tee the reception of a transmitted command the transmitter must start the telegram with
an adequate preburst. The required length of the preburst depends on the polling
parameters TSleep, TStartup, TBit-check and the start-up time of a connected microcontroller
(TStart,µC). Thus, TBit-check depends on the actual bit rate and the number of bits (NBit-check)
to be tested.
The following formula indicates how to calculate the preburst length.
TPreburst ³ TSleep + TStartup + TBit-check + TStart_µC
The length of period TSleep is defined by the 5-bit word Sleep of the OPMODE register,
the extension factor XSleep (according to Table 9), 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 to 1.
According to Table 8, the highest register value of sleep sets the receiver into a perma-
nent 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 and may also be used for microcontroller polling — via
Pin POLLING/_ON, the receiver can be switched on and off.
4569A–RKE–12/02
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet T5743.PDF ] | |
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