LMC567 datasheet(11/14 Pages) TI1

11 / 14 page

IN (PIN 3)

OUT (PIN 8)

INPUT

2.8 F

OSC

1.4 F

INPUT

OSC

2 F

LMC567

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SNOSBY1C – JUNE 1999 – REVISED DECEMBER 2015

10.2.2 Detailed Design Procedure

10.2.2.1 Timing Components

As VCO frequency (FOSC) runs at twice the frequency of the input tone, the desired input detection frequency can

be defined by Equation 7:

(7)

The central frequency of the oscillator is set by timing capacitor and resistor. The timing capacitor value (CT)

must be set in order to calculate the timing resistor value (RT). This is given by Equation 8:

(8)

So, in order to found the required component values to set the detection frequency Equation 9:

(9)

This approximation is valid with lower frequencies; considerations must be taken when using higher frequencies.

More information on this can be found in Oscillator.

10.2.2.2 Bandwidth

Detection bandwidth is represented as a percentage of FOSC. It can be approximated as a function of FOSC × C2

following the behavior indicated in Figure 4. More information on this can be found in Loop Filter.

10.2.2.3 Output Filter

The size of the output filter capacitor C1 is a tradeoff between slew rate and carrier ripple. More information on

this can be found in Output Filter.

10.2.2.4 Supply Decoupling

The decoupling of supply pin 4 becomes more critical at high supply voltages with high operating frequencies,

requiring C4 to be placed as close as possible to pin 4.

10.2.3 Application Curve

SPACE

Figure 9. Frequency Detection

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LMC567 Datasheet(PDF) 11 Page - Texas Instruments