Rainbow Electronics AT86RF231 - Manual (Page 13)

13
8111A–AVR–05/08
AT86RF231
the reference frequency, large parasitic capacitances should be avoided. Crystal lines should be
routed as short as possible and not in proximity of digital I/O signals. This is especially required
for the High Data Rate Modes, refer to
Section 11.3 “High Data Rate Modes” on page 137 .
Crosstalk from digital signals on the crystal pins or the RF pins can degrade the system perfor-
mance. Therefore, a low-pass filter (C3, R1) is placed close to the CLKM output pin to reduce
the emission of CLKM signal harmonics. This is not needed if the CLKM pin is not used as a
microcontroller clock source. In that case, the output should be turned off during device
initialization.
The ground plane of the application board should be separated into four independent fragments,
the analog, the digital, the antenna and the XTAL ground plane. The exposed paddle shall act as
the reference point of the individual grounds.
Table 5-1. Example Bill of Materials (BoM) for Basic Application Schematic
Designator Description Value Manufacture Part Number Comment
B1 SMD balun 2.4 GHz Wuerth 748421245
CB1
CB3 LDO VREG
bypass capacitor
1 µF
AVX
Murata 0603YD105KAT2A
GRM188R61C105KA12D X5R
(0603)
10% 16V
CB2
CB4
Power Supply decoupling
CX1, CX2 Crystal load capacitor 12 pF
AVX
Murata 06035A120JA
GRP1886C1H120JA01 COG
(0603)
5%
50V C1, C2 RF coupling capacitor 22 pF
Epcos
Epcos
AVX B37930
B37920
06035A220JAT2A COG 5%
(0402 or 0603)
C3
CLKM low-pass
filter capacitor
2.2 pF
AVX
Murata 06035A229DA
GRP1886C1H2R0DA01
COG
(0603)
±0.5 pF
Designed for f
CLKM
=1 MHz
C4 RF matching 0.47 pF Johnstech
R1
CLKM low-pass
filter resistor
680 Ω Designed for f
CLKM
=1 MHz
XTAL Crystal
CX-4025 16 MHz
SX-4025 16 MHz ACAL Taitjen
Siward XWBBPL-F-1
A207-011