CMX017 データシートの表示（PDF） - CML Microsystems Plc

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CMX017

UHF FM/FSK Transmitter

CML Microsystems Plc 

1.5 General Description

The CMX017 is a single chip UHF FM/FSK transmitter that combines both the RF VCO Modulator and

RF Power Amplifier. It is suitable for both audio FM and digital FSK transmissions.

A buffered oscillator output provides the RF signal drive to an external synthesizer or fixed frequency

phase-locked loop for channel frequency selection. Modulator output power is adjustable over a 20dB

range and the integrated power amplifier delivers up to +20dBm. The device also includes a powersave

mode: “Transmit Standby” and a zero-power mode: “Sleep”. These allow independent power down

control of both the modulator and power amplifier, thereby maximising battery life. The device can be

used in conjunction with the CMX018, a double-conversion super-heterodyne receiver, to implement a

complete UHF radio link.

1.5.1 FM/FSK Modulator + PA Driver

The modulator circuit uses an integrated oscillator whose frequency can be directly modulated by the

DC-coupled input base-band signal, at the MODIN pin, to generate a frequency modulated (FM or

FSK) RF signal. The oscillator requires an external varactor and resonator circuit, connected at the

TANK pin, to tune to the required RF channel. A buffered oscillator signal is provided from an open-

collector output, at the OSCOUT pin, to drive an external frequency synthesizer for the channel

selection.

The output power, at the MODOUT pin, is variable over a 20dB range. The output power is maximum

when the GAIN pin is connected to Vcc and is reduced by typically 20dB when this pin is connected to

0V. The output impedance at the MODOUT pin is typically 50Ω.

1.5.2 Power Amplifier (PA)

The power amplifier has two internal stages, each biased for class-B operation, and is designed to

have a fixed overall power gain. The input and output impedances can be terminated with 50Ω.

A typical power gain improvement of 2dB is achieved using simple external matching networks.

1.5.3 Powersave and Zero-Power Modes

The Modulator and Buffered Oscillator stages are powered down independently of the PA Driver and

Power Amplifier stages, by means of the ENLMOD and ENLPA logic inputs:

A logic '0' at ENLMOD powers down the Modulator and Buffered Oscillator stages.

A logic '0' at ENLPA powers down the PA Driver and Power Amplifier stages.

Refer to the block diagram in Figure 1 and to the Applications Section 1.6.2.

© 1999 Consumer Microcircuits Limited

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D/017/3

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