Evaluation Kit User Manual for CMX017

EV0171

© 1999 Consumer Microcircuits Limited

12

UM0171/2

1.6

Detailed Description

The EV0171 Evaluation Kit comprises a single board containing the CMX017 UHF FM/FSK

transmitter, frequency and gain potentiometers, VCO tank circuitry and miniature control switches.

A multi turn potentiometer allows the user to select an RF operating frequency between 860-

935MHz. The operating bandwidth and centre frequency can be adjusted by simply modifying the

VCO tank components.

The board is powered from a single 6 - 12 V dc power supply. Regulation circuitry sets the

analog(AV

CMX017 supply currents may be measured by removing

appropriate jumpers.

A low profile 2-way DIL switch controls the device enable lines, to obtain CMX017 powersave and

zero-power modes.

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 TP8 (OSCOUT) and TP9 after removal of

RV2.

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

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-JP3.

Note, due to the inductors dc resistance which is approximately 0.5

Ω (100nH), small voltage drops will

occur across inductors L3 and L1.

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 VCO Tank Circuitry

The tank resonator circuit is formed by two capacitors, C16 and C19, RG405 coaxial resonator, PR1,

and varacter diode, D1, which is driven by the frequency control potentiometer, RV2.

The dc control voltage derived from the frequency control potentiometer, RV2, can be measured at

TP9. Alternatively the potentiometer can be removed and control voltage applied to the VCO tank

circuitry via the test point TP9.