MC33596(2007) 데이터 시트보기 (PDF) - Freescale Semiconductor

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MC33596
(Rev.:2007)

PLL Tuned UHF Receiver for Data Transfer Applications

Freescale Semiconductor 

Frequency Planning

It is also possible to define two different configurations for the receiver (frequency, data rate, data manager,

modulation, etc.) that are automatically loaded during wakeup or under MCU control.

If the PLL goes out of lock, received data are ignored.

9 Frequency Planning

9.1 Clock Generator

All clocks running in the circuit are derived from the reference frequency provided by the crystal oscillator

(frequency fref, period tref). The crystal frequency is chosen in relation to the band in which the MC33596

has to operate. Table 4 shows the value of the CF bits.

Table 4. Crystal Frequency and CF Values Versus Frequency Band

RF

Frequency CF1

(MHz)

304

0

315

0

426

0

433.92

0

868.3

1

916.5

1

CF0

LOF1

LOF0

FREF (Crystal

Frequency)

(MHz)

FIF (IF

Frequency)

(MHz)

Dataclk Fdataclk Digclk

Divider (kHz) Divider

Fdigclk

(kHz)

Tdigclk

(µs)

0

0

0

16.96745

0

1

0

17.58140

1

0

1

23.74913

1

0

1

24.19066

1

0

1

24.16139

1

1

1

25.50261

1.414

1.465

1.484

1.512

1.510

1.594

60 282.791 30 565.582 1.77

60 293.023 30 586.047 1.71

80 296.864 40 593.728 1.68

80 302.383 40 604.767 1.65

80 302.017 40 604.035 1.66

80 318.783 40 637.565 1.57

9.2 Intermediate Frequency

The IF filter is controlled by the crystal oscillator to guarantee the frequency over temperature and voltage

range. The IF filter center frequency, FIF, can be computed using the crystal frequency fref and the value

of the CF bits:

• If CF[0] = 0 : FIF = fref/9*1.5/2

• If CF[0] = 1 : FIF = fref/12*1.5/2

The cut-off frequency given in the parametric section can be computed by scaling to the FIF.

Example 1. Cut-off Frequency Computation

Compute the low cut-off frequency of the IF filter for a 16.9683 MHz crystal oscillator. For this

reference frequency, FIF = 1.414 MHz.

So, the 1.3751 MHz low cut-off frequency specified for a 1.5 MHz IF frequency becomes

1.3751*1.414/1.5 = 1.296 MHz

1. Refer to parameter 3.3 found in Section 18.1, “General Parameters.”

MC33596 Data Sheet, Rev. 3

8

Freescale Semiconductor

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