U3741BM-M2FLG3 TEMIC [TEMIC Semiconductors], U3741BM-M2FLG3 Datasheet - Page 3

• Manufacturer Part Number: U3741BM-M2FLG3
• Description: UHF ASK/FSK Receiver
• Manufacturer: TEMIC [TEMIC Semiconductors]

Rev. A1, 15-Oct-98
Block Diagram
RF Front End
The RF front end of the receiver is a heterodyne
configuration that converts the input signal into a 1-MHz
IF signal. According to figure 3, the front end consists of
an LNA (low noise amplifier) 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
controlled oscillator) generates the drive voltage
frequency f
voltage at Pin LF. f
frequency is compared to f
detector. The current output of the phase frequency
detector is connected to a passive loop filter and thereby
generates the control voltage V
LO
for the mixer. f
LNAGND
FSK/ASK
MIXVCC
LNA_IN
LO
CDEM
AGND
DGND
AVCC
SENS
is divided by factor 64. The divided
XTO
XTO
LF
LNA
LO
. The VCO (voltage-
by the phase frequency
for the VCO. By means
is dependent on the
Preliminary Information
RSSI
and data filter
Demodulator
FSK/ASK–
4. Order
IF Amp
IF Amp
3 MHz
3 MHz
LPF
LPF
Figure 3. Block diagram
Limiter out
Sensitivity
reduction
DEMOD_OUT
of that configuration V
f
calculated using the following formula:
The XTO is a one-pin oscillator that operates at the series
resonance of the quartz crystal. According to figure 4, the
crystal should be connected to GND via a capacitor CL.
The value 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
and hereby of f
of receiving bandwidth, the accuracy of the crystal and
the XTO must be considered.
LO
f
VCO
/64 is equal to f
64
Standby logic
f
XTO
Polling circuit
control logic
FE
= f
and
LO
LO
XTO
/64
. When designing the system in terms
XTO
CLK
50 k
. If f
W
LF
V
LO
is controlled in a way that
S
U3741BM
is determined, f
DATA
ENABLE
TEST
POUT
MODE
DVCC
LFGND
LFVCC
XTO
LF
15011
XTO
3 (25)
can be
XTO