RFPIC12C509AG Microchip Technology Inc., RFPIC12C509AG Datasheet - Page 41

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

7.6
The PLL output feeds the power amplifier (PA). The
open-collector differential output (ANT1, ANT2) can be
used to drive a loop antenna directly or converted to
single-ended output via an impenance matching net-
work or balanced-to-unbalanced (balun) transformer.
Pins ANT1 and ANT2 are open-collector outputs and
must be pulled-up to V
The differential output of the PA should be matched to
an impedance of 1 k
will cause excessive spurious and harmonic emissions.
The transmit output power can be adjusted in six dis-
crete steps from +2 dBm to -12 dBm by varying the volt-
age (V
example voltage divider network for ASK operation and
Figure 7-7 for FSK operation.
For FSK operation, the PS/DATA
a Power Select (PS) pin. An internal 20
source pushes current through the PS/DATA
resulting in a voltage drop across resistor R2 at the V
level selected for transmitter output power. V
the PA bias current. Higher transmit power will draw
higher current.
For ASK operation, the function of the PS/DATA
is to turn the Power Amplifier (PA) on and off. Resistors
R1 and R2 form a voltage divider network to apply volt-
age V
maximum transmitter output is desired, the output of a
GP0 pin can be connected directly to PS/DATA
TABLE 7-5:
©
2001 Microchip Technology Inc.
Note 1: Standard Operating Conditions (unless otherwise stated) T
Output Power
Transmitter
PS
PS
(dBm)
) at the PS/DATA
Power Amplifier
-10
-12
-60
2: V
3: The Power Select circuitry contains an internal 20 A current source. To ensure that the transmitter output
for the selected transmitter output power. If
+2
-1
-4
-7
V
power is at the minimum when transmitting a DATA
that the voltage drop across it is less than 0.1 volts.
DDRF
PS
is actual voltage on PS/DATA
POWER SELECT
= 3V, f
DDRF
Failure to match the impedance
Operating Current
ASK
TRANSMIT
Transmitter
through the load.
pin. Figure 7-6 shows an
(mA)
11.5
<4.8
8.6
7.3
6.2
5.3
4.8
ASK
= 433.92 MHz
pin only serves as
(1)
PS
A current
ASK
Power Select (PS)
ASK
ASK
selects
ASK
Voltage V
.
pin.
Preliminary
pin
pin
(Volts)
PS
<0.1
1.2
0.9
0.7
0.5
0.3
2.0
rfPIC12C509AG/509AF
(2)
PS
Table 7-5 lists typical values for R1 and R2 for both the
ASK and FSK modes.
FIGURE 7-6:
FIGURE 7-7:
ASK
DATA IN
= 0 (V
A
R1 ( )
OPEN
2400
6800
11K
15K
24K
43K
= 25°C, RF
SSRF
), select the value of resistor R2 such
R1
EXAMPLE FSK POWER
EXAMPLE ASK POWER
SELECT CIRCUIT
SELECT CIRCUIT
ASK
EN
PS/DATA
R2
R2 ( )
= 1,
V
PS
4700
4700
4700
4700
4700
4700
4700
ASK
PS/DATA
R2
(3)
V
PS
rfPIC12C509AF
ASK
20
DS70031A-page 39
A
To power
select
circuitry
rfPIC12C509AG
20
R2 ( )
4700
FSK
A
56K
47K
39K
27K
15K
75K
To power
select
circuitry