MCH12140, MCK12140

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4

APPLICATIONS INFORMATION

The 12140 is a high speed digital circuit used as a phase

comparator in an analog phase-locked loop. The device

determines the “lead” or “lag” phase relationship and time

difference between the leading edges of a VCO (V) signal

and a Reference (R) input. Since these edges occur only once

per cycle, the detector has a range of

±2p radians.

The operation of the 12140 can best be described using the

plots of Figure 2. Figure 2 plots the average value of U, D

and the difference between U and D versus the phase

difference between the V and R inputs.

There are four potential relationships between V and R: R

lags or leads V and the frequency of R is less than or greater

than the frequency of V. Under these four conditions the

12140 will function as follows:

Figure 2. Average Output Voltage vs. Phase Difference

2

−2p

−pp

2p

U

Fv > Fr

R lags V

Fv < Fr

R leads V

2

D

2

U−D

2

−2p

−pp

2p

−2p

−pp

2p

R lags V in phase

When the R and V inputs are equal in frequency and the

phase of R lags that of V the U output will stay HIGH while

the D output will pulse from HIGH to LOW. The magnitude

of the pulse will be proportional to the phase difference

between the V and R inputs reaching a minimum 50% duty

cycle under a 180

° out of phase condition. The signal on D

indicates to the VCO to decrease in frequency to bring the

loop into lock.

V frequency > R frequency

When the frequency of V is greater than that of R the

12140 behaves in a similar fashion as above. Again the

signal on D indicates that the VCO frequency must be

decreased to bring the loop into lock.

R leads V in phase

When the R and V inputs are equal in frequency and the

phase of R leads that of V the D output will stay HIGH while

the U output pulses from HIGH to LOW. The magnitude of

the pulse will be proportional to the phase difference

between the V and R inputs reaching a minimum 50% duty

cycle under a 180

° out of phase condition. The signal on U

indicates to the VCO to increase in frequency to bring the

loop into lock.

V frequency < R frequency

When the frequency of V is less than that of R the 12140

behaves in a similar fashion as above. Again the signal on U

indicates that the VCO frequency must be decreased to bring

the loop into lock.

From Figure 2 when V and R are at the same frequency and

in phase the value of U − D is zero thus providing a zero error

voltage to the VCO. This situation indicates the loop is in lock

and the 12140 action will maintain the loop in its locked state.

ORDERING INFORMATION

Device

Package

MCH12140D

SOIC−8

98 Units / Rail

MCH12140DG

SOIC−8

(Pb−Free)

98 Units / Rail

MCH12140DR2

SOIC−8

2500 / Tape & Reel

MCH12140DR2G

SOIC−8

(Pb−Free)

2500 / Tape & Reel

MCK12140D

SOIC−8

98 Units / Rail

MCK12140DG

SOIC−8

(Pb−Free)

98 Units / Rail

MCK12140DR2

SOIC−8

2500 / Tape & Reel

MCK12140DR2G

SOIC−8

(Pb−Free)

2500 / Tape & Reel

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.