EV0181 Datasheet, PDF (12/18 Pages) CML Microcircuits – User Manual

Evaluation Kit User Manual for CMX018
EV0181
1.6 Detailed Description
The EV0181 Evaluation Kit comprises a single board containing the CMX018 UHF FM/FSK receiver,
frequency control potentiometer, VCO tank circuitry, IF filters, 79.3MHz overtone Colpitts crystal
oscillator, tuned 10.7MHz quadrature tank circuit, miniature control switches and audio amplifier.
A multi-turn potentiometer allows the user to select an RF operating frequency between 860-935MHz.
The operating bandwidth and centre frequency can be optimised by modifying the VCO tank
components.
The board is powered from a single 6-12V dc power supply. Regulation circuitry sets the analog(AV_DD)
supply for 3V operation. CMX018 supply current may be measured by removing the appropriate
jumper.
A low profile 2-way DIL switch controls the device enable and gain select lines.
Links, test points and SMA connector provide access to various points in the circuit.
This open-loop configuration is not recommended for the majority of customer applications. A closed-
loop PLL design is required to improve controllability and overcome stability and drift problems.
External PLL circuitry could be connected to test points TP11 (OSCOUT) and TP14. This
configuration also requires the capacitor C29 to be fitted and inductor L8 removed.
Alternatively PCB footprints are provided to allow the user drive the VCO externally from a stable
source to overcome frequency drift due to the frequency control potentiometer, RV1.
1.6.1 Hardware Description
1.6.1.1 Operating Voltage
The supply regulation circuitry contains a single regulator and associated components to provide the
analog supply (AV_DD). The operating voltage is set to 3.0V.
The supply feed is split three ways to reduce interference and to enable the user to separately
measure various device/circuitry currents.
The supply regulation can be bypassed and external supplies applied, via jumpers JP1 - JP2.
1.6.1.2 Current Measurement
Supply currents for the evaluation device and other board circuitry can be measured by removing the
appropriate jumper and replacing it with a multimeter.
1.6.1.3 RF Input and LNA
The RF SMA input connector, RFIN, J1, is connected to the LNAIN pin of the CMX018 via a 100pF ac
coupling capacitor. This capacitor can be removed and replaced by a low loss front end bandpass
SAW filter, whose frequency response is application specific.
The six pad SAW filter footprint employed in the EV0181 layout is compatible with a large range of
SAW filter devices available from various manufacturers.
© 1999 Consumer Microcircuits Limited
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