MICRF221 Ver la hoja de datos (PDF) - Micrel

Número de pieza

componentes Descripción

Fabricante

MICRF221

3.3V, QwikRadio® 850 MHz to 950 MHz Receiver

Micrel 

Micrel Inc.

D0

D1

D2 MODE: Desense

0

X

X No Desense - default

1

0

0 7dB Desense

1

1

0 19dB Desense

1

0

1 32dB Desense

1

1

1 42dB Desense

Reference Control

There are two components in the Reference and

Control sub-block: 1) Reference Oscillator and 2)

Control Logic, Serial Interface and Parallel Inputs.

Reference Oscillator

RO2

C

V BIAS

R

RO1

C

Figure 4. MICRF221 Reference Oscillator Circuit

MICRF221

The reference oscillator in the MICRF221 uses a

basic Pierce crystal oscillator configuration with MOS

transconductor to provide negative resistance.

MICRF221 has built-in load capacitors for the crystal

oscillator, shown in Figure 4, even though external

load capacitors are still needed for tuning to the right

frequency. RO1 and RO2 are external pins of the

MICRF221 and are to connect to the reference

oscillator crystal.

The reference oscillator crystal frequency can be

calculated as follows:

FREF OSC = FRF/(64 + 1.1/12)

For 868.35 MHz,

FREF OSC = 13.54856 MHz

For 915 MHz

FREF OSC = 14.27643 MHz

To operate the MICRF221 with minimum offset,

crystal frequencies should be specified with 10pF

loading capacitance.

October 2008

9

M9999-100108

(408) 955-1690

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