MICRF220 Ver la hoja de datos (PDF) - Micrel

Número de pieza

componentes Descripción

Fabricante

MICRF220

300MHz to 450MHz, 3.3V ASK/OOK Receiver with RSSI and Squelch

Micrel 

Micrel, Inc.

RO2

C

RO1

C

V BIAS

R

MICRF220

Figure 5. Reference Oscillator Circuit

Reference oscillator crystal frequency can be calculated

according to Equation 3. For example, if fRF = 433.92MHz,

fREF = 13.52313MHz. Table 4 lists the values of reference

frequencies at different popular RF frequencies. To

operate the MICRF220 with minimum offset, use proper

loading capacitance recommended by the crystal

manufacturer.

Figure 6. Data Out Pin with No Squelch (VSQ = VDD)

RF Input Frequency (MHz)

315.0

390.0

418.0

433.92

Reference Frequency (MHz)

9.81713*

12.15446

13.02708

13.52313*

*Empirically derived, slightly different from Equation 3.

Table 4. Reference Frequency Examples

When squelch function is enabled by tying the SQ pin low,

the chip will monitor incoming pulse width before allowing

activity on DO pin. The pulse width is set by SEL1 and

SEL0 pins as shown in Table 5, and is inversely

proportional to frequency. When there is no input signal

and squelch is not enabled (SQ pin left floating), voltage on

DO chatters due to random noise as shown in Figure 6. If

SQ pin is tied low, the activity on DO pin is much reduced

as shown in Figure 7.

Squelch Operation

When squelch function is enabled by tying the SQ pin low,

the chip will monitor incoming pulse width before allowing

activity on DO pin. The pulse width is set by SEL1 and

SEL0 pins as shown in Table 5, and is inversely

proportional to frequency. When there is no input signal

and squelch is not enabled (SQ pin left floating), voltage on

DO chatters due to random noise as shown in Figure 6. If

SQ pin is tied low, the activity on DO pin is much reduced

as shown in Figure 7.

Figure 7. Data Out Pin with Squelch (VSQ = 0V)

August 2010

11

M9999-082610-A

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