MC33492 查看數據表（PDF） - Motorola => Freescale

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MC33492

PLL Tuned UHF Transmitter for Data Transfer Applications

Motorola => Freescale 

Freescale SMeCm33ic49o2nductor, Inc.

TRANSMITTER FUNCTIONAL DESCRIPTION

MC33492 is a PLL tuned low power UHF transmitter. The different modes of operation are controlled by the

microcontroller through several digital input pins. The power supply voltage ranges from 1.9V to 3.6V allowing

operation with a single lithium cell.

PHASE LOCKED LOOP AND LOCAL OSCILLATOR

The VCO is a completely integrated relaxation oscillator. The Phase Frequency Detector (PFD) and the loop

filter are fully integrated. The exact output frequency is equal to: fRFOUT = fXTAL x PLL divider ratio. The frequency

band of operation is selected through the BAND pin.

Table 1 provides details for each frequency band selection.

Table 1: Frequency band selection and associated divider ratios

BAND input level

Frequency

band (MHz)

PLL divider

ratio

Crystal oscillator

frequency (MHz)

High

Low

315

32

434

868

64

9.84

13.56

An out-of-lock function is performed by monitoring the PFD output voltage. When it exceeds its limits, the RF

output stage is disabled.

RF OUTPUT STAGE

The output stage is a single ended square wave switched current source. Harmonics will be present in the

output current drive. Their radiated absolute level depends on the antenna characteristics and output power.

Typical application demonstrates compliance to ETSI standard.

A resistor Rext connected to the REXT pin controls the output power allowing a tradeoff between radiated

power and current consumption.

The output voltage is internally clamped to Vcc ±2Vbe (typ. Vcc ±1.5V @ TA=25°C).

MODULATION

A low logic level has to be applied on pin MODE, to select the On Off Keying (OOK) modulation. This

modulation is performed by switching on/off the RF output stage. The logic level applied on pin DATA controls the

output stage state:

DATA=0 -> output stage off

DATA=1 -> output stage on

MICROCONTROLLER INTERFACE

Four digital input pins (ENABLE, DATA, BAND and MODE) enable the circuit to be controlled by a

microcontroller. It is recommended to configure the band frequency and the modulation type before enabling the

circuit. In a typical application the input pin MODE is hardwired to ground. To reduce total current consumption, it

is recommended to connect pin BAND according to the following table 2.

Table 2: Digital pins connecting recommendation

434MHz Frequency band BAND = I/O or ENABLE

868MHz Frequency band

BAND = GND

One digital output (DATACLK) provides to the microcontroller a reference frequency for data clocking. This

frequency is equal to the crystal oscillator frequency divided by 64 (see table 3).

Table 3: DATACLK frequency versus crystal oscillator frequency

Crystal oscillator frequency (MHz)

DATACLK frequency (kHz)

9.84

154

13.56

212

For More Information On This Product,

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