SL1710
+j1
+j0.5
+j2
+j0.2
+j5
Marker
Zreal
Zimag
1 480MHz
= 75.7
= –36.4
0
0.2
0.5
1
2
5
–j0.2
–j5
–j0.5
–j1
–j2
START 350 MHz
STOP 650 MHz
Fig.4 Typical RF input impedance
APPLICATION NOTES
These application notes should be read in conjunction with
the circuit diagram Fig 3. and the PCB layout illustrated in Figs
9 and 10. An alternative oscillator configuration using a SAW
Resonator is shown in the circuit diagram Fig. 11 and the PCB
layout illustrated in Figs 12 and 13. These boards have been
designed to permit the initial evaluation of the SL1710
performance.
SAW RESONATOR OSCILLATOR
The application detailed in Fig. 11 shows an SL1710 with
a SAW Resonator controlled oscillator. In this instance the
frequency accuracy and stability of the oscillator are
determined by the Saw Resonator. The PCB detailed in Figs.
12 and 13 is designed to accommodate the following SAWR;
Manufacturer
MURATA
Part No
SAR479.45MB10X200
VARACTOR TUNED
The application detailed in Fig.3 uses a synthesised VCO.
The tuning range of the oscillator is;
Varactor line Voltage.
5 Volts
30 Volts
Oscillator Frequency
458MHz
504MHz
PRESCALER OUTPUTS
The VCO frequency/32 is available at the differential
prescaler outputs pins 10 and 11. This enables the on board
VCO to be synthesised via a PLL.
VCO DISABLE
The on-chip oscillator can be disabled by connecting the
VCO Disable (pin 15) to ground and enabled by connecting the
pin to V
CC
via a 4K7 pull up resistor.
This configuration gives a VCO sensitivity of 1.84MHz/
Volt. The inductor L1 is a 12nF surface mount component.
Different VCO centre frequencies and sensitivities can be
achieved by changing the values of L1, C12 and C13.
The VCO frequency is controlled by the SP5611
synthesiser which is programmed via an I
2
C bus. The RF
input to the synthesiser is from the SL1710 prescaler outputs
via RF inductors L3 and L4.
AGC
The DC voltage measured at TP1 should be adjusted using
VR1 to read 2.5 volts with respect to V
EE
. this voltage equates
to the nominal centre of the AGC control curve. The control
voltage applied to pin 1 can be varied between 0.5 Volts
(maximum gain) and V
CC
-0.5 Volts minimum gain)
5
MITEL [ MITEL NETWORKS CORPORATION ]
