FX105A Datasheet, PDF (11/16 Pages) CML Microcircuits – Tone Detector

Tone Detector
FX105A
1.6.2.10 Calculation of PLL Filter Phase Shift
Capacitor C₄ is used to phase shift the input to the VCO commutating filter by 30°, thus shifting the
sampling clocks by the same amount. This enables the "Word" sampling filter to sample and integrate
at the maxima and minima of the input tone.
C₄ = tan (30°) / [2p f₀ R_V] » 0.092 / [f₀ R_V] » 164pF
1.6.3
Replacement for FX105
Figure 6 depicts the circuit changes required to replace a FX105 with a FX105A device. A 5V zener
diode and a resistor can be used to generate a 5V supply voltage from an existing 12V supply. If the
Detect Output needs to pull up beyond the 5V supply, a transistor amplifier following the output can
be used.
Figure 6 Circuit changes for 12V to 5V conversion
© 1999 Consumer Microcircuits Limited
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