© 1999 Consumer Microcircuits Limited

9

D/017/3

1.6.2

Powersave and Zero-Power Modes

It is possible to power down each section of the transmitter independently. This feature may be useful

when the CMX017 is configured, with the CMX018, as a radio transceiver. It allows the transmitter to

be powered on and off, thereby saving power, during the sleep and standby periods.

In SLEEP mode (ENLMOD = '0' and ENLPA = '0') all sections of the device are powered down and the

current consumption is reduced to less than 10

µA. This is the zero-power mode.

In TRANSMIT-STANDBY mode (ENLMOD = '1' and ENLPA = '0') only the PA Driver and Power

Amplifier stages are powered down, whilst the Modulator and Buffered Oscillator remain active. This

powersave mode allows the external frequency synthesizer to stabilise the channel centre -frequency

prior to the RF transmission.

In TRANSMIT mode (ENLMOD = '1' and ENLPA = '1') both the Modulator and Power Amplifier

sections of the device are fully operational.

Note: The device can be used as a stand alone “UHF Power Amplifier” by forcing (ENLMOD = '0' and

ENLPA = '1'). The efficiency is maximised by connecting the Vcc2 pin to 0V. (The Vcc1 pin must

remain connected to 3.0V.)

1.6.3

Lower Output Power Applications

For very short range applications the antenna drive can be taken from the modulator output, MODOUT,

at pin 26. The Power Amplifier is powered down by connecting Vcc3 and Vcc4 (pins 1 and 12) to 0V.

This allows the supply current to be minimised and the Modulator output to be enabled or disabled

using the ENLPA input at pin 13.

1.6.4

Example Schematic and Layout

The following schematic (Figure 3) and printed circuit layout (Figure 4) show a typical application

interface for the CMX017. To aid legibility, the schematic and layout are available electronically from

the CML website http://www.cmlmicro.co.uk or on floppy disk by request from CML's office.

Alternative components and component values are shown on the schematic. These should be

selected according to the intended application. The schematic uses the following ICs:

U2

IC Works

WB1315X

U4

Analog Devices AD8532-SO8