RFPIC12C509AG Microchip Technology Inc., RFPIC12C509AG Datasheet - Page 38

• Manufacturer Part Number: RFPIC12C509AG
• Description: 18/20-pin 8-bit Cmos Microcontroller With Uhf Ask/fsk Transmitter
• Manufacturer: Microchip Technology Inc.

OUT is high-impedance effectively coupling only
capacitor C1 to the crystal and the resulting transmit
frequency equals f
is grounded to V
Selecting the appropriate values for C1 and C2 sets the
center frequency and frequency deviation. Capacitor
C1 sets f
rfPIC12C509AG/509AF
7.3.2
The rfPIC12C509AF crystal oscillator can be config-
ured for FSK operation. Figure 7-3 shows an example
FSK circuit. Capacitors C1 and C2 achieve FSK modu-
lation by pulling the crystal. When DATA
C1. The resulting transmit frequency will equal f
f
ship. The transmit center frequency f
TABLE 7-3:
FIGURE 7-3:
DS70031A-page 36
MIN
Note 1: Standard Operating Conditions (unless otherwise stated) T
. The graph in Figure 7-4 illustrates this relation-
MAX
C1 (pF)
CRYSTAL OSCILLATOR FSK
OPERATION
100
f
22
33
39
47
68
XTAL
and capacitors C1 and C2 in parallel set
SSRF
= 13.55 MHz
TYPICAL TRANSMIT CENTER FREQUENCY AND FREQUENCY DEVIATION
(FSK MODE)
EXAMPLE FSK EXTERNAL
CRYSTAL CIRCUIT
MAX
and will parallel capacitor C2 with
X1
C1
. When DATA
C2
Freq (MHz) / Dev (kHz)
XTAL
FSKOUT
rfPIC12C509AF
(1)
C2 = 1000 pF
433.612 / 34
433.604 / 25
433.598 / 20
433.596 / 17
433.593 / 13
433.587 / 8
FSK
C
is defined as:
FSK
= 0, FSKOUT
= 1, FSK-
MIN
Preliminary
.
Freq (MHz) / Dev (kHz)
The frequency deviation of the transmit frequency is
defined as:
FIGURE 7-4:
Layout considerations - Avoid parallel traces in order
to reduce circuit stray capacitance. Keep traces as
short as possible. Isolate components to prevent cou-
pling. Use ground traces to isolate signals.
433.601 / 11.5
C2 = 100 pF
433.619 / 27
433.610 / 19
433.604 / 14
433.598 / 9
f
Frequency
c
f
(MHz)
—
Fmax
A
f
Fmin
f
max
max
= 25°C, RF
2
DATA
2
f
f
min
min
FSK
VERSUS CHANGE IN
TRANSMITTED FREQUENCY
LOAD CAPACITANCE
C1
= 1 DATA
EN
Load Capacitance (pF)
©
= 1, V
C1||C2
2001 Microchip Technology Inc.
Freq (MHz) / Dev (kHz)
FSK
DDRF
433.600 / 5.5
433.625 / 21
433.614 / 14
433.608 / 10
C2 = 47 pF
433.604 / 8
= 0
= 3V,
—