MRF24XA_15 Datasheet, PDF (10/258 Pages) Microchip Technology – Low-Power, 2.4 GHz ISM-Band IEEE 802.15.4™ RF

MRF24XA
2.4.1 POWER AND GROUND PINS
Table 2-3 lists the recommended bypass capacitors. VDD
pins 29 and 30 are power pins, which require different
bypass capacitors to ensure sufficient bypass decoupling
and stability. Bypass capacitors must have low serial
resistance. The 4.7 µF capacitors must be made of
ceramic or high-performance tantalum.
On PCB layout minimize trace length from the VDD pin
to the bypass capacitors and connect capacitors to the
pads as short as possible. PCB tracks must be wide
enough to minimize voltage drop and serial inductance
of the power line.
Analog and digital power lines must follow a star topol-
ogy, where the common point is the bypass capacitor
on pin 30.
TABLE 2-3: RECOMMENDED BYPASS CAPACITOR VALUES
VDD Pin
1
29
30
Symbol
AVDD
VREGOUT
VREGIN
Bypass Capacitor
3.3 pF
4.7 μF
10 nF + 4.7 µF
2.4.2 16 MHz MAIN OSCILLATOR PINS
The 16 MHz oscillator is connected to OSC1 and OSC2
pins as shown in Figure 2-2, which provides the
reference frequency for the internal RF, MAC and BB
circuitry. Table 2-4 lists the crystal parameters.
To minimize parasitic effects on pins, the crystal must
be put as close as possible to MRF24XA. It keeps the
tracks short. Crystal must be surrounded with ground
pour to minimize cross coupling effects. Crystal load
capacitors must be placed close to the crystal.
TABLE 2-4: 16 MHz CRYSTAL PARAMETERS⁽¹⁾
Parameters
Frequency
Frequency tolerance for 500, 250 and 125 kbps data rates (including manufac-
turing aging and temperature)
Frequency tolerance for 2 and 1 Mbps data rates (including manufacturing
aging and temperature)
Mode
Load Capacitance
ESR
Note 1: IEEE 802.15.4 defines ±40 ppm.
2: These values are only used for design guidance .
Value
16 MHz
±60 ppm⁽¹⁾
±40 ppm⁽²⁾
Fundamental
18 pF
80 Ohm max
FIGURE 2-2:
16 MHz MAIN OSCILLATOR CRYSTAL CIRCUIT
CL1
OSC1
X1
CL2
OSC2
16 MHz
Main Oscillator
DS70005023C-page 10
Preliminary
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