RFHCS362G_11 Datasheet, PDF (27/54 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder with UHF ASK/FSK Transmitter

6.3.1
CRYSTAL OSCILLATOR ASK
OPERATION
The rfHCS362G/362F crystal oscillator can be config-
ured for ASK operation. Figure 6-1 shows an example
ASK circuit.
Capacitor C1 trims the crystal load capacitance to the
desired circuit load capacitance and places the crystal
on the desired frequency.
rfHCS362G/362F
FIGURE 6-1: EXAMPLE ASK EXTERNAL
CRYSTAL CIRCUIT
XTAL
X1
rfHCS362G/
362F
C1
TABLE 6-2: XTAL OSC APPROXIMATE FREQ. VS. CAPACITANCE (ASK MODE) ⁽¹⁾
C1
Predicted Frequency
(MHz)
PPM from 13.55 MHz
Transmit Frequency (MHz)
(32 * fXTAL)
22 pF
13.551438
+106
433.646
39 pF
13.550563
+42
433.618
100 pF
13.549844
-12
433.595
150 pF
13.549672
-24
433.5895
470 pF
13.549548
-33
433.5856
1000 pF
13.549344
-48
433.579
Note 1: Standard Operating Conditions (unless otherwise stated) TA = 25°C, RFEN = 1, VDDRF = 3V,
fXTAL = 13.55 MHz
© 2011 Microchip Technology Inc.
DS41189B-page 27