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
µ
A. 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
U4
IC Works
WB1315X
Analog Devices AD8532-SO8
©
1999
Consumer Microcircuits Limited
9
D/017/3
CMLMICRO [ CML MICROCIRCUITS ]
