MICRF211 datasheet(10/18 Pages) MICREL

10 / 18 page

Micrel

MICRF211

March 2007

M9999-030107

(408) 944-0800

Crystal Y1 or Y1A (SMT or leaded respectively) is the

reference clock for all the device internal circuits.

Crystal characteristics of 10pF load capacitance,

30ppm, ESR < 50

Ω, -40ºC to +105ºC temperature

range are desired. Table 5 shows the crystal

frequencies and one of Micrel’s approved crystal

manufacturers (www.hib.com.br).

The oscillator of the MICRF211 is a Colpitts type. It is

very sensitive to stray capacitance loads. Thus, very

good care must be taken when laying out the printed

circuit board. Avoid long traces and ground plane on

the top layer close to the REFOSC pins RO1 and

RO2. When care is not taken in the layout, and

crystals from other vendors are used, the oscillator

may take longer times to start as well as the time to

good data in the DO pin to show up. In some cases, if

the stray capacitance is too high (> 20pF), the

oscillator may not start at all.

The crystal frequency is calculated by REFOSC = RF

Carrier/(32+(1.1/12)). The local oscillator is low side

injection (32 × 13.52127MHz = 432.68MHz), that is,

its frequency is below the RF carrier frequency and

the image frequency is below the LO frequency. See

Figure 6

. The product of the incoming RF signal and

local oscillator signal will yield the IF frequency, which

will be demodulated by the detector of the device.

Figure 6. Low Side Injection Local Oscillator.

REFOSC (MHz)

Carrier (MHz)

HIB Part Number

12.15269

390.0

SA-12.152690-F-10-H-30-30-X

13.02519

418.0

SA-13.025190-F-10-H-30-30-X

13.52127

433.92

SA-13.521270-F-10-H-30-30-X

Table 5. Crystal Frequency and Vendor Part Number.

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