T5760-TGQ Atmel, T5760-TGQ Datasheet - Page 4

• Manufacturer Part Number: T5760-TGQ
• Description: IC RX 868MHZ ISM ASK/FSK 20-SOIC
• Manufacturer: Atmel

Specifications of T5760-TGQ

• Frequency: 868MHz
• Sensitivity: -110dBm
• Data Rate - Maximum: 10 kBaud
• Modulation Or Protocol: ASK, FSK
• Applications: General Purpose Data Transmission Systems
• Current - Receiving: 7.8mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 105°C
• Package / Case: 20-SOIC (0.300", 7.50mm Width)
• Operating Temperature (min): -40C
• Operating Temperature (max): 105C
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -
• Memory Size: -
• Lead Free Status / Rohs Status: Not Compliant
• Other names: T5760-TGQTR

RF Front End
4
T5760/T5761
The RF front end of the receiver is a low-IF heterodyne configuration that converts the
input signal into a 950 kHz/1 MHz IF signal with an image rejection of typical 30 dB.
According to Figure 3 the front end consists of an LNA (Low Noise Amplifier), LO (Local
Oscillator), I/Q mixer, polyphase lowpass filter and an IF amplifier.
The PLL generates the carrier frequency for the mixer via a full integrated synthesizer
with integrated low noise LC-VCO (Voltage Controlled Oscillator) and PLL-loop filter.
The XTO (crystal oscillator) generates the reference frequency f
VCO generates two times the mixer drive frequency f
are generated with a divide by two circuit (f
and feeds into a phase frequency detector and compared with f
phase frequency detector is fed into an integrated loop filter and thereby generates the
control voltage for the VCO. If f
ing formula:
f
The XTO is a one-pin oscillator that operates at the series resonance of the quartz
crystal with high current but low voltage signal, so that there is only a small voltage at
the crystal oscillator frequency at Pin XTAL. According to Figure 4, the crystal should be
connected to GND with a series capacitor C
mended by the crystal supplier. Due to a somewhat inductive impedance at steady state
oscillation and some PCB parasitics a lower value of C
The value of C
value of f
find the right value for this capacitor) and hereby of f
terms of receiving bandwidth and local oscillator accuracy, the accuracy of the crystal
and the XTO must be considered.
If a crystal with ±30 ppm adjustment tolerance at 25°C, ±50 ppm over temperature
-40°C to +105°C, ±10 ppm of total aging and a CM (motional capacitance) of 7 fF is
used, an additional XTO pulling of ±30 ppm has to be added.
The resulting total LO tolerance of ±120 ppm agrees with the receiving bandwidth
specification of the T5760/T5761 if the T5750 has also a total LO tolerance of
±120 ppm.
Figure 4. XTO Peripherals
The nominal frequency f
frequency f
f
XTO
LO
= f
= f
RF
LO
- f
/128
XTO
IF
IF
using the following formula (low side injection):
(the best way is to use a crystal with known load resonance frequency to
L
should be optimized for the individual board layout to achieve the exact
LO
is determined by the RF input frequency f
LO
is determined, f
TEST 3
TEST 2
DVCC
XTAL
n.c.
V
LO
S
= f
L
. The value of that capacitor is recom-
VCO
XTO
/2). f
can be calculated using the follow-
LO
VCO
C
L
L
. When designing the system in
VCO
is normally necessary.
. The I/Q signals for the mixer
is divided by a factor of 256
XTO
XTO
. The integrated LC-
. The output of the
RF
4561B–RKE–10/02
and the IF