7

AT86RF211

1942C–WIRE–06/02

Detailed Description

Frequency Synthesis

Crystal Reference Oscillator

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

canbeused.

Note:

The PLL is activated only when the oscillator is stabilized.

Figure 5. Crystal Oscillator Inputs

Figure 6. Typical Networks

Notes:

must be re-calculated.

2. Thanks to the fine steps of the synthesizer (200 Hz), the trimmer capacitor can be replaced by a software adjustment.

Synthesizer

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.

XTAL1

XTAL2

C1 = 82 pF

C2 = 56 pF

XTAL1

XTAL2

CL = 16 pF

15 pF

6.5/30 pF

C1 = 68 pF

XTAL1

XTAL2

CL = 20 pF

33 pF

6.5/30 pF

C2 = 68 pF

(1)

(2)

(1)

(2)