ATA5744 ATMEL Corporation, ATA5744 Datasheet - Page 3

• Manufacturer Part Number: ATA5744
• Description: Ata5744 Uhf Ask Receiver
• Manufacturer: ATMEL Corporation

Figure 2-2.
3. RF Front End
4893A–RKE–11/05
Block Diagram
LNAGND
The RF front end of the receiver is a heterodyne configuration that converts the input signal into
a 1-MHz IF signal. According to
fier), LO (Local Oscillator), a mixer and RF amplifier.
The LO generates the carrier frequency for the mixer via a PLL synthesizer. The XTO (crystal
oscillator) generates the reference frequency f
erates the drive voltage frequency f
is divided by factor 64. The divided frequency is compared to f
tor. The current output of the phase frequency detector is connected to a passive loop filter and
thereby generates the control voltage VLF for the VCO. By means of that configuration, VLF is
controlled in a way that f
the following formula:
f
The XTO is a one-pin oscillator that operates at the series resonance of the quartz crystal.
According to
of that capacitor is recommended by the crystal supplier. The value of CL should be optimized
for the individual board layout to achieve the exact value of f
ing the system in terms of receiving bandwidth, the accuracy of the crystal and the XTO must be
considered.
MIXVCC
XTO
LNA_IN
CDEM
AGND
DGND
AVCC
RSSI
= f
LO
/64
LNA
Figure
BR_0
and data filter
Demodulator
RSSI IF Amp
3-1, the crystal should be connected to GND via a capacitor CL. The value
4. Order
IF Amp
ASK-
3 MHz
3 MHz
LPF
LPF
BR_1
RSSI
LO
/64 is equal to f
Dem_out
Figure
LO
f
VCO
for the mixer. f
2-2, the front end consists of an LNA (Low-Noise Ampli-
64
XTO
Data interface
. If f
XTO
Standby logic
Test
. The VCO (Voltage-Controlled Oscillator) gen-
LO
XTO
LO
is determined, f
is dependent on the voltage at pin LF. f
XTO
XTO
DATA
TEST
MODE
DVCC
ENABLE
LFGND
LFVCC
XTO
LF
and hereby of f
by the phase frequency detec-
XTO
can be calculated using
LO
ATA5744
. When design-
LO
3