at86rf211 ATMEL Corporation, at86rf211 Datasheet - Page 7

• Manufacturer Part Number: at86rf211
• Description: Fsk Transceiver For Ism Radio Applications
• Manufacturer: ATMEL Corporation

Detailed Description
Frequency Synthesis
Crystal Reference Oscillator
Figure 6. Typical Networks
Notes:
Synthesizer
1942C–WIRE–06/02
C L = 16 pF
1. Various load capacitance (C
2. Thanks to the fine steps of the synthesizer (200 Hz), the trimmer capacitor can be replaced by a software adjustment.
must be re-calculated.
(1)
15 pF
XTAL1
C1 = 82 pF
6.5/30 pF
The reference clock is based on a classical Colpitts architecture with three external
capacitors.
An XTAL with load capacitor in the range of 10 pF - 20 pF is recommended. The bias
circuitry of the oscillator is optimized to produce a low drive level for the XTAL. This
reduces XTAL aging. Any standard, parallel mode 10.245 MHz or 20.945 MHz crystal
can be used.
Note:
Figure 5. Crystal Oscillator Inputs
A high-speed, high-resolution multi-loop synthesizer is integrated. The synthesizer can
operate within two frequency bands: 400 MHz to 480 MHz and 800 MHz to 950 MHz. All
channels in these two bands can be selected through software programming (registers
F0 to F3). All circuitry is on-chip with the exception of the PLL loop filter. The phase
comparison is made thanks to a charge pump topology. Typical charge pump current is
225 µA.
L
) crystals can be used. In case C
(2)
The PLL is activated only when the oscillator is stabilized.
XTAL2
C2 = 56 pF
XTAL2
C L = 20 pF
L
XTAL1
differs of 16 pF or 20 pF, the surrounding network (C1, C2)
33 pF
(1)
XTAL1
C1 = 68 pF
6.5/30 pF
(2)
AT86RF211
XTAL2
C2 = 68 pF
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