RFPIC12F675F-I/SS Microchip Technology, RFPIC12F675F-I/SS Datasheet - Page 53

• Manufacturer Part Number: RFPIC12F675F-I/SS
• Description: IC MCU 1KX14 RF FSK/ASK 20SSOP
• Manufacturer: Microchip Technology
• Series: PIC®r

Specifications of RFPIC12F675F-I/SS

• Package / Case: 20-SSOP
• Frequency: 380MHz ~ 450MHz
• Applications: RKE, Security Systems
• Modulation Or Protocol: ASK, FSK
• Data Rate - Maximum: 40 kbps
• Power - Output: 10dBm
• Current - Transmitting: 14mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Memory Size: 1024 x 14 words Flash, 128 x 8 Byte EEPROM, 64 x 8 Byte SRAM
• Voltage - Supply: 2V ~ 5.5V
• Operating Temperature: -40°C ~ 125°C
• Processor Series: RFPIC12F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 64 B
• Interface Type: USB
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 6
• Number Of Timers: 2
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Development Tools By Supplier: ICE2000, DV164102, AC164101, AC164103
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 4-ch x 10-bit
• Program Memory Type: Flash
• Program Memory Size: 1.75 KB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: XLT20SS-1 - SOCKET TRANSITION 18DIP 20SSOPAC164103 - MODULE RCVR RFPIC 433MHZAC164101 - MODULE TRANSMITTER RFPIC 433MHZDV164102 - KIT DEV RFPICKIT KIT 1AC124002 - MOD SKT PROMATEII 18SOIC/20SSOP
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: Q3188156

9.5
In FSK modulation the transmit data is sent by varying
the output frequency. This is done by loading the
reference crystal with extra capacitance to pull it to a
slightly lower frequency which the PLL then tracks.
Switching the capacitance in and out with the data
signal toggles the transmitter between two frequencies.
These two crystal based frequencies are then
multiplied by 32 for the RF transmit frequency.
Unlike the ASK transmit frequency the FSK center
frequency is not actually transmitted. It is the artificial
point
frequencies, calculated with this formula.
The other important parameter in FSK is the frequency
deviation of the transmit frequency. This measures how
far the frequency will swing from the center frequency.
Single ended deviation is calculated with this formula.
An FSK receiver will specify its optimal value of
deviation. The single ended deviation must be greater
than data rate/4. The minimum deviation is usually
limited by the frequency accuracy of the transmitter and
receiver components. The maximum deviation is usually
limited by the pulling characteristics of the transmitter
crystal.
An extra capacitor and the internal switch are added to
the ASK design to build an FSK transmitter as shown
in Figure 9-3. The C1 capacitor in series with the crystal
determines the maximum frequency.
With the DATA
the C2 capacitor does not affect the frequency. When
the DATA
and the C2 is thrown in parallel with C1. The sum of the
two caps pulls the oscillation frequency lower as shown
in Figure 9-4.
TABLE 9-3:
 2003 Microchip Technology Inc.
Note 1: Standard Operating Conditions, T
half
FSK Modulation
FSK
C1 (pF)
100
22
33
39
47
68
way
pin goes low, FSK
FSK
∆
TYPICAL TRANSMIT CENTER FREQUENCY AND DEVIATION (FSK MODE)
f
pin high the FSK
c
f
between
=
=
f
f
max
max
2
+
−
2
Freq (MHz) / Dev (kHz)
the
f
OUT
f
min
min
OUT
C2 = 1000 pF
433.612 / 34
433.604 / 25
433.598 / 20
433.596 / 17
433.593 / 13
433.587 / 8
two
shorts to ground,
pin is open and
transmitted
A
= 25°C, RF
Preliminary
Freq (MHz) / Dev (kHz)
EN
= 1, V
In FSK mode the DATA
enable the PA. The FSK circuit is shown in Figure 9-6.
Use accurate crystals for narrow bandwidth systems
and large values for C1 to reduce frequency drift.
FIGURE 9-3:
FIGURE 9-4:
433.601 / 11.5
C2 = 100 pF
433.619 / 27
433.610 / 19
433.604 / 14
433.598 / 9
Frequency
(MHz)
DDRF
—
Fmax
Fmin
= 3V, f
DATA
XTAL
FSK CRYSTAL CIRCUIT
FREQUENCY PULLING
FSK
C1
X1
C1
= 1 DATA
rfPIC12F675
Load Capacitance (pF)
= 13.55 MHz
C2
ASK
C1||C2
Freq (MHz) / Dev (kHz)
pin should be tied high to
FSK
433.600 / 5.5
433.625 / 21
433.614 / 14
433.608 / 10
rfPIC12F675K/F/H
XTAL
FSKOUT
C2 = 47 pF
433.604 / 8
= 0
DS70091A-page 51
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