RFPIC12C509AG Microchip Technology Inc., RFPIC12C509AG Datasheet - Page 35

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

7.0
7.1
The transmitter is a fully integrated UHF ASK/FSK
transmitter consisting of crystal oscillator, phase-
locked loop (PLL), open-collector differential-output
Power Amplifier (PA), and mode control logic. External
components consist of bypass capacitors, crystal, and
PLL loop filter. The rfPIC12C509AG is capable of
Amplitude Shift Keying (ASK) modulation. The
rfPIC12C509AF is capable of ASK or Frequency Shift
Keying (FSK) modulation by employing an internal FSK
switch to pull the transmitter crystal via a second load
capacitor.
Figure 7-1 shows the internal structure of the transmit-
ter. Transmitter connections are independent from the
PICmicro microcontroller unit (MCU) to provide for
maximum design flexibility. Example application cir-
cuits for ASK or FSK modulation are presented at the
end of this section.
The rfPIC12C509AG/509AF are radio frequency (RF)
emitting devices. Wireless RF devices are governed by
a country’s regulating agency. For example, in the
United States it is the Federal Communications Com-
mittee (FCC) and in Europe it is the European Confer-
ence
Administrations (CEPT). It is the responsibility of the
designer to ensure that their end product conforms to
rules and regulations of the country of use and/or sale.
TABLE 7-1:
©
RF devices require correct board level implementa-
tion in order to meet regulatory requirements. Layout
considerations are listed at the end of each subsec-
tion. It is best to place a ground plane on the PCB to
reduce radio frequency emmissions and cross talk.
f
C
C
ESR
These values are for design guidance only.
XTAL
2001 Microchip Technology Inc.
L
O
Sym
UHF ASK/FSK TRANSMITTER
Transmitter Operation
of
Crystal Frequency
Load Capacitance
Shunt Capacitance
Equivalent Series Resistance
Postal
CRYSTAL PARAMETERS
Characteristic
and
Telecommunications
9.69
Min
10
—
—
Preliminary
Max
60
15
15
7
rfPIC12C509AG/509AF
7.2
Pins V
respectively to the transmitter. These power pins are
separate from power supply pins V
PICmicro MCU.
7.3
The transmitter crystal oscillator is a Colpitts oscillator
that provides the reference frequency to the PLL. It is
independent from the PICmicro oscillator. An external
crystal or AC coupled reference signal is connected to
the XTAL pin. The transmit frequency is fixed and
determined by the crystal frequency according to the
formula:
Due to the flexible selection of transmit frequency, the
resulting crystal frequency may not be a standard off-
the-shelf value. Therefore, for some carrier frequencies
the designer will have to consult a crystal manufacturer
and have a custom crystal manufactured. Crystal
parameters are listed in Table 7-1. For background
information on crystal selection see Application Note
AN588, PICmicro
Guide.
The crystal oscillator start time (t
Table 11-10, Transmitter AC Characteristics.
Layout Considerations - Provide low impedance
power and ground traces to minimize spurious emis-
sions. A two-sided PCB with a ground plane on the
bottom layer is highly recommended. Separate
bypass capacitors should be connected as close as
possible to each of the supply pins V
Connect V
separate PCB vias. Do not share a PCB via with mul-
tiple ground traces.
Units
f
MHz
transmit
pF
pF
DDRF
Supply Voltage (V
Crystal Oscillator
SS
f
and V
XTAL
Parallel Resonant Mode
and V
®
SSRF
Microcontroller Oscillator Design
Conditions
32
SSRF
supply power and ground
to the ground plane using
DDRF
DD
DS70031A-page 33
on
, V
DD
and V
) is listed in
SSRF
and V
SS
)
DDRF
to the
.